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In this study, FeCo 2 O 4 @Co 3 O 4 bifunctional catalysts with a unique structure combining nanosheets and nanowires were prepared on nickel foam by a simple hydrothermal + annealing method. The catalysts exhibited excellent catalytic activity for hydrogen production during urea electrooxidation reaction (UOR) and ethanol oxidation reaction (EOR). For UOR, the potential at 10 mA/cm2 current density is 1.387 V and the tafel slope is 67 mV/dec. In the configured two-electrode electrolytic cell, the FeCo 2 O 4 @Co 3 O 4 catalysts in the UOR and EOR processes required only 1.425 and 1.471 V, respectively, to produce a current density of 10 mA/cm2, which is much less than that of the (oxygen evolution reaction) OER (1.640 V). In addition, the current density remained stable at a fixed potential during a long time (20 h) i-t test in the urea solution. [Display omitted] • FeCo 2 O 4 @Co 3 O 4 nanocomposites were synthesized by a two-step hydrothermal + annealing method. • FeCo 2 O 4 @Co 3 O 4 electrode showed better electrocatalytic properties of UOR and EOR than that of OER. • FeCo 2 O 4 @Co 3 O 4 /NF//Pt electrolyzer displayed low potentials and stable long cycle life. • The study presented a promising FeCo 2 O 4 @Co 3 O 4 electrode for energy-saving H 2 production. [ABSTRACT FROM AUTHOR]

Nickel‐based catalysts have been regarded as one of the most promising electrocatalysts for urea oxidation reaction (UOR), however, their activity is largely limited by the inevitable self‐oxidation reaction of Ni species (NSOR) during the UOR. Here, we proposed an interface chemistry modulation strategy to trigger the occurrence of UOR before the NSOR via constructing a 2D/2D heterostructure that consists of ultrathin NiO anchored Ru−Co dual‐atom support (Ru‐Co DAS/NiO). Operando spectroscopic characterizations confirm this unique triggering mechanism on the surface of Ru‐Co DAS/NiO. Consequently, the fabricated catalyst exhibits outstanding UOR activity with a low potential of 1.288 V at 10 mA cm−2 and remarkable long‐term durability for more than 330 h operation. DFT calculations and spectroscopic characterizations demonstrate that the favorable electronic structure induced by this unique heterointerface endows the catalyst energetically more favorable for the UOR than the NSOR. [ABSTRACT FROM AUTHOR]

The urine/urea oxidation reaction through catalysts with a higher performance in direct urea microfluidic fuel cells (DUµFC) is a promising method for power generation due to the large amount of human and animal urine containing 2–2.5 wt% urea. This paper presents a study that used urea as fuel in a DUµFC in the presence of palladium supported by reduced graphene oxide (rGO) for power generation. Some parameters, such as urea, KOH and H2SO4 concentration and flux rate, among others, are optimized in order to carry out the evaluation of urine samples as fuel in an air-breathing microfluidic fuel cell. The results show that the Pd/rGo catalyst mixed with Nafion® in the anodic compartment is dispersed and attached to the paper fibers, generating electrical contact and giving rise to the reactions of interest. In addition, XRD analysis confirmed the successful deposition of Pd and rGo on the substrate. These electrochemical results are promising, since, despite the decrease in the general performance of the DUµFC under ideal conditions with respect to normal cells, the generation of energy from urine was demonstrated. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) urea splitting is of great significance for urea wastewater remediation and hydrogen production with low energy consumption simultaneously. Nickel hydroxides as electrocatalysts have been widely investigated for urea electrolysis. However, it is an open question how to synthesize highly catalytic Ni(OH)2 for the PEC urea splitting. Herein, we take advantage of the instability of metal–organic frameworks (MOFs) to perform an in situ synthesis of Ni(OH)2 catalysts on the surface of TiO2 nanorod arrays. This transformed Ni(OH)2 (T-Ni(OH)2) possesses a superior PEC catalytic activity for water/urea splitting in comparison to the Ni(OH)2 prepared by the impregnation method. The in situ transition of a Ni-MOF is accomplished through an electrochemical treatment under AM1.5G illumination in a KOH-and-urea mixed electrolyte. The specific transition mechanism of Ni-MOFs is the substitution of ligands with OH− in a 1 M KOH electrolyte and the successive phase transition. The T-Ni(OH)2@TiO2 photoanode delivers a high photocurrent density of 1.22 mA cm−2 at 1.23 VRHE, which is 4.7 times that of Ni(OH)2@TiO2 prepared with the impregnation method. The onset potential of T-Ni(OH)2@TiO2 is negatively shifted by 118 mV in comparison to TiO2. Moreover, the decline of photocurrent during the continuous test can be recovered after the electrochemical and light treatments. [ABSTRACT FROM AUTHOR]

Urea oxidation reaction (UOR) is a promising substitution of oxygen evolution reaction (OER) in overall water splitting technology because of the lower theoretical potential; thereby, a win-win benefit is achieved due to the simultaneous hydrogen generation and water purification. The efficient UOR catalysis substantially depends on the exposed active sites and mass transfer resistance, especially at high current density to meet the requirement of industrial water splitting technology. In this work, we have synthesized α-Ni(OH) 2 porous nanoflowers (α-Ni(OH) 2 –PNF) using ZIF-67 as template. Ascribing to the Kirkendall effect, nanopores are created on α-Ni(OH) 2 nanosheets benefiting for the formation of abundant oxygen vacancies as well as drop-off in mass transfer resistance during UOR catalysis. Meanwhile, the binding strength between active site and CO 2 , rate-determining step of UOR, is weakened by oxygen vacancies; as a result, only 1.477 V vs. RHE is demanded for α-Ni(OH) 2 –PNF to catalyze UOR with 100 mA cm−2, 67 mV lower than α-Ni(OH) 2 nanosheets. Besides, an exceptional stability is also achieved for α-Ni(OH) 2 –PNF with negligible degradation during 20 h catalysis. • α-Ni(OH) 2 porous nanoflowers are synthesized using ZIF-67 as sacrificed template. • α-Ni(OH) 2 –PNF exhibits more oxygen vacancies due to the porous structure. • Binding strength between active sites and CO 2 is loosened ascribed to abundant oxygen vacancies. [ABSTRACT FROM AUTHOR]

The Co 8 FeS 8 @CoFe–MOF/NF heterojunction array with abundant phase interface was formed on the surface of nickel foam (NF) via a simple solvothermal method for water and urea splitting. The designed Co 8 FeS 8 @CoFe–MOF/NF heterojunction electrocatalyst exhibits superior activity towards oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and urea oxidation reaction (UOR), which only requires low overpotentials of 213 mV, 191 mV and 81 mV to reach a current density of 10 mA cm−2, respectively. Moreover, it shows low cell voltages of 1.62 V and 1.55 V at 10 mA cm−2 for overall water and urea splitting, respectively. [Display omitted] Designing efficient electrocatalysts to improve the overall water splitting and urea electrolysis efficiency for hydrogen generation can greatly solve the dilemma of energy shortage and environmental pollution. In this work, Co 8 FeS 8 @CoFe–MOF/NF heterojunction arrays were fabricated by embedding sulfides into the surface of metal-organic frameworks (MOFs) nanosheets as multifunctional electrocatalyst. The introduction of sulfide on CoFe–MOF/NF can not only adjust the electronic structure (electron-rich state) and change the surface properties (more hydrophilic), but also increase the active area to enhance the catalytic activity. The in situ Raman shows Co 8 FeS 8 @CoFe–MOF/NF is more easily to generate active species at low potentials and generates a higher content of active β-MOOH phase than CoFe–MOF/NF. Therefore, the Co 8 FeS 8 @CoFe–MOF/NF exhibits excellent oxygen evolution reaction (OER) performance with an overpotential of 213 mV at 10 mA cm−2. Furthermore, when used as a urea oxidation reaction (UOR), only an ultralow potential of 1.311 V at 10 mA cm−2. More importantly, the assembled two-electrode drives overall water splitting and urea electrolysis with cell voltages of 1.62 V and 1.55 V at 10 mA cm−2, respectively. This work provides insights into the preparation of electrocatalysts with multifunctional heterostructure arrays for hydrogen production. [ABSTRACT FROM AUTHOR]

Defect and interface engineering has been established as efficient methods for altering the electrical structure and improving the activity of electrocatalysts. Here, a rational design architecture consisting of Ni 2 P nanoparticles embedded in P-doped carbonized wood fibers (Ni 2 P/PCWF) is synthesized by simultaneous carbonization and phosphorization. A synergistic enhancement effect between electronic structure manipulation and interface regulation is observed in Ni 2 P/PCWF during the urea oxidation reaction (UOR). First, the P doping of carbon can optimize the electronic structure of Ni 2 P/PCWF. Second, the charge transport process is aided by the Ni 2 P nanoparticles embedded in the PCWF. Lastly, electron transfer can be accelerated by the in-situ formed heterogeneous interface between metal phosphides and metal hydroxides (hydroxyl oxides). Due to the synergy of the structural and electrical modulation, Ni 2 P/PCWF exhibits remarkable electrocatalytic properties toward the UOR under alkaline conditions. It only requires 1.34 V (vs. RHE) to achieve a current density of 50 mA cm−2, and the increase in potential at 10 mA cm−2 for 70 h is insignificant (≈2.9%). This work supports the development of new strategies using sustainable, renewable wood fibers to develop excellent UOR catalysts for energy-saving H 2 generation. [Display omitted] • A simple simultaneous phosphorization and carbonization strategy is developed to synthesize Ni 2 P/PCWF. • P doping into the carbon matrix can induce additional defects in carbon. • Metal phosphides/metal hydroxide heterogeneous interface was in-situ formed during the UOR process. • Ni 2 P/PCWF exhibits outstanding electrocatalytic performance for UOR. [ABSTRACT FROM AUTHOR]

Developing highly efficient bifunctional urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) catalysts for urea splitting to hydrogen are one of the strategies to cope with the energy crisis. Here, a series of Cr x P y -a/Co m P n -b composites were synthesized on Ni foam through hydrothermal and low-temperature phosphorization process for the first time. It is worth noting that Cr x P y -1/Co m P n -3@NF exhibited excellent UOR performance (1.331 V at 100 mA cm−2) and HER performance (0.299 V at 100 mA cm−2) in an electrolyte of 1 M KOH and 0.5 M urea due to the synergistic effect of Cr–Co. The Cr x P y -1/Co m P n -3@NF||Cr x P y -1/Co m P n -3@NF two-electrode system call for only 1.52 V to provide current density of 10 mA cm−2, which is one of the best electrochemistry performances reported up to now. Experimental analysis show that the promoted electrochemistry performances is assigned to faster charge transfer rate, the exposure of more reaction site and better properties of metals. Density Functional theory (DFT) results demonstrate that the presence of the Co m P n material accelerates the kinetics of hydrogen production and the Cr x P y material improves the properties of metals for the electrode. The work provides a new idea to develop the environmentally friendly and low cost overall urea splitting catalyst with transition metals instead of noble metals. The Cr x P y -1/Co m P n -3@NF||Cr x P y -1/Co m P n -3@NF two-electrode system call for only 1.52 V to provide current density of 10 mA cm−2, which is one of the best electrochemistry performances reported up to now. [Display omitted] • A series of Cr x P y -a/Co m P n -b composites were synthesized on Ni foam through hydrothermal process. • Cr x P y -1/Co m P n -3@NF exhibited excellent UOR performance (1.331 V at 100 mA cm−2) and HER performance (0.299 V at 100 mA cm−2). • The work provides a new idea to develop the environmentally friendly and low cost overall urea splitting catalyst. [ABSTRACT FROM AUTHOR]

Water electrolysis is known as an efficient strategy in the direction of green energy production to remove fossil fuels and generate hydrogen. On the other hand, the slow kinetics of the anodic half-reaction (OER) significantly reduces the efficiency of this system. Therefore, choosing an alternative to OER has become a new and reliable approach. Urea oxidation reaction (UOR) is considered an excellent alternative to OER due to its low required potential (0.37V), the abundance of urea sources (industrial waste and human/animal urine), and harmless by-products (N 2 , CO 2). Electrocatalysts based on non-noble metals such as nickel, cobalt, molybdenum, manganese, iron, and copper in electrochemical urea-assisted water splitting due to their high electrocatalytic performance and lower price than noble metals play an essential role in reducing costs and increasing the efficiency of this system. This review investigated the electrochemical water splitting reaction and its anodic and cathodic half-reactions. Then, urea, electro-oxidation of urea, methods of making catalysts, measuring parameters of electrocatalytic properties, solutions to improve performance, and types of non-noble catalysts used in this field were reviewed, and finally, challenges and solutions to improve results in the future were introduced. • Hydrogen production efficiency can be enhanced assisted by urea oxidation reaction. • Different HER, OER and UOR mechanisms have been addressed in this article. • Recent advances in catalysts for UOR assisted hydrogen production was reviewed. [ABSTRACT FROM AUTHOR]

Simple Summary: It is vitally important that scientists are able to describe their work simply and concisely to the public, especially in an open access online journal. The simple summary consists of no more than 200 words in one paragraph and contains a clear statement of the problem addressed, the aims and objectives, pertinent results, conclusions from the study, and how they will be valuable to society. This should be written for a lay audience, i.e., no technical terms without explanations. No references are cited, and no abbreviations included. Submissions without a simple summary will be returned directly. Developing renewable energy sources and controlling water pollution are critical but challenging problems. Urea oxidation (UOR) and methanol oxidation (MOR), both of which have high research value, have the potential to effectively address wastewater pollution and energy crisis problems. A three-dimensional neodymium-dioxide/nickel-selenide-modified nitrogen-doped carbon nanosheet (Nd2O3-NiSe-NC) catalyst is prepared in this study by using mixed freeze-drying, salt-template-assisted technology, and high-temperature pyrolysis. The Nd2O3-NiSe-NC electrode showed good catalytic activity for MOR (peak current density ~145.04 mA cm−2 and low oxidation potential ~1.33 V) and UOR (peak current density ~100.68 mA cm−2 and low oxidation potential ~1.32 V); the catalyst has excellent MOR and UOR characteristics. The electrochemical reaction activity and the electron transfer rate increased because of selenide and carbon doping. Moreover, the synergistic action of neodymium oxide doping, nickel selenide, and the oxygen vacancy generated at the interface can adjust the electronic structure. The doping of rare-earth-metal oxides can also effectively adjust the electronic density of nickel selenide, allowing it to act as a cocatalyst, thus improving the catalytic activity in the UOR and MOR processes. The optimal UOR and MOR properties are achieved by adjusting the catalyst ratio and carbonization temperature. This experiment presents a straightforward synthetic method for creating a new rare-earth-based composite catalyst. [ABSTRACT FROM AUTHOR]

In this paper, a porous nitrogen-doped carbon was firstly covered on nickel foam, which was followed by high-temperature vapor deposition with DPPF to obtain Fe-doped Ni 12 P 5 nanorod arrays for urea oxidation reaction. The characterizations revealed that the DPPF-induced growth of nickel phosphide has the structure of straight nanorods with a length of up to tens of micrometers, and the composition can be identified as Fe-doped Ni 12 P 5. [Display omitted] Synthesis of regular morphology catalysts with self-growing substrates is one of the effective methods to solve the problem of easy shedding of heterogeneous catalysts. In this study, Fe-doped Ni 12 P 5 nanorods were prepared by depositing 1,1′ -bis (diphenylphosphine) ferrocene (DPPF) on N-doped C/NF. The bottom-up growth of the nanorod is ascribed to the preferential adsorption of DPPF with a P site to NF that is surface-doped with the solid-solving C, and the length of nanorods can reach tens of microns and has good robustness. The N-doped carbon-constrained rod-shaped Fe-doped Ni 12 P 5 catalyst (Fe-Ni 12 P 5 /N d C/NF-800) that grows on NF has excellent catalytic performance for the urea oxidation reaction. In addition, the current density can be maintained as high as 100 mA cm−2 and the current attenuation is weak for 12 h, and the rod shape remains good. This work provides a new idea for synthesizing self-growing catalysts with regular morphology to improve the performance of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Binder-free nickel–cobalt phosphate (NiCoPO) micro flakes are evenly grown on the nickel foam (NF) by a simple hydrothermal method, which can act as a highly efficient bifunctional electrocatalyst (NiCoPO/NF) for both oxygen evolution reaction (OER) and urea oxidation reaction (UOR). NiCoPO/NF presents the relatively prominent OER and UOR activities with ultralow potentials of 1.51 V and 1.34 V (vs. reversible hydrogen electrode) to reach the current density of 100 mA cm−2, respectively. The outstanding UOR and OER performance of NiCoPO/NF might be attributed to the fact that the successful incorporation of oxygen atoms into Ni/Co phosphate is beneficial for the oxidation of metal atoms at high overpotential. In addition, NF can improve the electrical conductivity to accelerate the electron transfer from the electrode to the catalyst. Additionally, in the alkaline solution (1 M KOH), NiCoPO/NF shows excellent durability and stability after the consecutive OER and UOR tests for 48 h. The design of NiCoPO/NF would pave the way to construct more efficient bifunctional electrodes for electrocatalytic water splitting with or without urea in alkaline solution, which provides a novel technological platform for the conversion of human waste into the sustainable energy. [ABSTRACT FROM AUTHOR]

The overall energy efficiency of electrochemical systems is severely hindered by the traditional anodic oxygen evolution reaction (OER). Utilizing urea oxidation reaction (UOR) with lower thermodynamic potential to replace OER provides a promising strategy to enhance the energy efficiency. Amorphous and heterojunctions electrocatalysts have been aroused extensive studies owing to their unique physicochemical properties and outperformed activity. Herein, we report a simple method to construct a novel crystalline—amorphous NiO-CrOx heterojunction grown on Ni foam for UOR electrocatalyst. The NiO-CrOx electrocatalyst displays excellent UOR performance with an ultralow working potential of 1.32 V at 10 mA·cm−2 and ultra-long stability about 5 days even at 100 mA·cm−2. In-situ Raman analysis and temperature-programmed desorption (TPD) measurement verify that the presence of the amorphous CrOx phase can boost the reconstruction from NiO to active NiOOH species and enhance adsorption ability of urea molecule. Besides, the unique crystalline—amorphous interfaces are also benefit to improving the UOR performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ferrocene-based MOF was phosphorized to construct electrocatalyst. • The prepared CoFeP/MOF catalyst displays outstanding OER and UOR performance. • The catalytic performances of MOFs can be greatly enhanced via phosphorization. • A new strategy for the improvement of high-performance water-splitting catalysts. Developing high-performance and inexpensive water-splitting electrocatalysts is crucial for addressing current energy and environmental issues. In this work, a ferrocene (Fc)-based metal organic framework (MOF) was rationally phosphorized to construct a CoFeP/MOF composite electrocatalyst. Thanks to the excellent conductivity, high specific surface area, and rich heterojunction interfaces, the prepared catalyst exhibits outstanding catalytic activity and long-term endurance, which can realize 50 mA cm−2 at an overpotential of 246 mV for oxygen evolution reaction (OER) in 1.0 M KOH and a cell potential of 1.441 V (vs. RHE) for urea oxidation reaction (UOR) in 1.0 M KOH and 0.5 M urea. The electrolyzer assembled from the prepared electrode and Pt/C electrode can drive 50 mA cm−2 at 1.605 V and 1.524 V (vs. RHE) in the overall/urea-assisted water splitting tests, demonstrating great application prospects. This work provides valuable reference for improving the performance of MOF type bifunctional water electrolysis catalysts. [ABSTRACT FROM AUTHOR]

Ni is regarded as active site for provoking urea oxidation reaction (UOR); nevertheless, monometallic Ni-based catalysts can not possess sufficiently high performance owing to poisoning susceptibility of Ni towards carbonaceous intermediates and the poor electrical conductivity. In response, NiS x -VS 4 -C is synthesized via a facile glycerol coking strategy in hydrothermal system. It is found that NiS x -VS 4 -C is composed of many nanoparticles with a relatively small size (approximately 70 nm). Besides acting as the precursor of carbon, glycerol can regulate the morphology and structure of catalysts, and promote the formation of vacancy defects. Using as catalyst for UOR, a specific current activity of 652 mA cm−2 mg−1 for NiS x -VS 4 -C can be achieved at 0.52 V (vs. Hg/HgO), which is much higher than that for NiS x or VS 4 synthesized in glycerol solution. Glycerol coking is important for boosting catalytic activity. NiS x -VS 4 -C synthesized in glycerol solution exhibits much better catalytic activity than that synthesized in other alcohol solutions. Potential dependent impedance analyses reveal that urea indirect electro-oxidation mechanism should be mainly obeyed when NiS x -VS 4 -C is employed as catalyst. Both Ni and V with high chemical valence are active sites, where Ni species is mainly in charge of the oxidation of amine intermediate and V species is mainly in charge of the oxidation of CO intermediate. Carbon, especially graphitized phase, will significantly enhance the electrical conductivity and accelerate the charge transfer process. Therefore, constructing dual active sites and enhancing electrical conductivity via polyalcohol coking provide promising strategies for Ni-based catalysts towards UOR. [Display omitted] • NiS x -VS 4 -C is synthesized via a facile glycerol coking strategy in hydrothermal system. • NiS x -VS 4 -C exhibits superior catalytic performance towards UOR. • Ni species can facilitate the oxidation of ammine intermediate. • V species can facilitate the oxidation of CO intermediate. • The existence of carbon plays a vital role in promoting the charge transfer process. [ABSTRACT FROM AUTHOR]

The escalating demand for clean energy has intensified the pursuit of efficient hydrogen production methods. The urea emerges as an alternative to traditional electrolysis. Despite the inherent sluggish kinetics posed by the 6-electron transfer process, Ni-based catalysts have demonstrated remarkable potential in accelerating urea oxidation reaction (UOR) kinetics. This comprehensive review focuses on Ni and its hydroxide/oxide derivatives as promising electrocatalysts for the UOR, key to facilitating the transition to a hydrogen-based economy. It underscores the critical role of Ni-based materials in enhancing UOR kinetics, with an emphasis on the development of innovative synthetic approaches and the manipulation of material structures to optimize catalytic performance. The paper encapsulates the mechanisms of UOR catalysis, the impact of nanostructuring, and the integration of heteroatoms to boost activity. By examining recent advances and identifying future directions, this review sets the stage for the advancement of Ni-based catalysts for efficient hydrogen production via urea electrolysis. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Identified UOR active states over nickel-based catalysts: The high UOR overpotentials on Ni-based catalysts originate from the Ni3+ state formation via electrochemical structural reconstruction. • Element doping to reduce barriers of the Ni 3+ state generation: The Mn doping optimizes the electronic states and intercalation of guest anions weakens the interlayer interactions, which ultimately tunes Ni 3+ generation kinetics toward the superior UOR activity. • In-situ spectroscopic methods to confirm the UOR mechanism: The urea molecule is completely oxidized via multi-step processes including deprotonation of amino group, intermolecular or intramolecular N-N coupling, and nucleophilic substitution. Reducing the urea oxidation reaction (UOR) barriers is a key knot for accelerating its practical applications. Here, we demonstrate that NiMn-LDH with sulfate anion interaction can enable urea electrooxidation with a low anodic potential of 1.36 V at 100 mA cm−2. We find that the UOR on NiMn-LDH is driven by Ni3+ species and the Ni3+ generation is the rate-determining step of UOR. Both the Mn doping and sulfate anion interaction contribute to the low-barrier phase transformation from Ni(OH) 2 to NiOOH to produce the Ni3+ state with high activity in UOR, owing to that Mn doping optimizes the electronic states and intercalation of guest anions weakens the interlayer interactions, which ultimately tunes Ni3+ generation kinetics toward the superior UOR activity. Our findings provide new insights into the design of the highly active UOR catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Hydrogen production by electrocatalytic water splitting is considered to be an effective and environmental method, and the design of an electrocatalyst with high efficiency, low cost, and multifunction is of great importance. Herein, we developed a crystalline NiFe phosphide (NiFeP)/amorphous P-doped FeOOH (P-FeOOH) heterostructure (defined as P-NiFeO x H y) as a high-efficiency multifunctional electrocatalyst for water electrolysis. The NiFeP nanocrystals provide remarkable electronic conductivity and plenty of active sites, the amorphous P-FeOOH improves the adsorption energy of oxygen-containing species, and the crystalline/amorphous heterostructure with superhydrophilic and superaerophobic surface generates synergistic effects, providing plentiful active sites and efficient charge/mass transfer. Benefiting from this, the designed P-NiFeO x H y displays ultralow overpotentials of 159.2 and 20.8 mV to achieve 10 mA cm−2 for oxygen evolution reaction and hydrogen evolution reaction, and also shows the superior performance of urea oxidation reaction with a low voltage of 1.37 V at 10 mA cm−2 in 1 M KOH with 0.33 M urea. In-situ Raman spectra and ex-situ XPS analysis were also used to investigate the catalytic process and reveal the surface structure evolution of P-NiFeO x H y under electrochemical oxidation. Accordingly, the designed P-NiFeO x H y is employed as both cathode and anode to assemble into the urea-assisted water electrolysis device, which can reach 10 mA cm−2 with a low 1.36 V and could be further driven by a solar cell. The work reveals a design of superior activity, cost-effective and multifunctional electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Urea electrolysis is regarded as a prospective method for energy-saving hydrogen production. However, the practical application of this technology is limited by the lack of high-performance bifunctional catalysts for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Herein, a heterostructure catalyst composed of NiFe layered double hydroxide (LDH) and sulfides (NiFe LDH-NiFeSx/NF) catalysts is prepared via a simple one-step hydrothermal approach. Remarkably, the prepared NiFe LDH-NiFeSx/NF required 138 mV and 1.34 V to achieve 10 mA cm−2 for HER and UOR in 1 M KOH and 0.33 M urea, respectively. Furthermore, when NiFe LDH-NiFeSx/NF is used as a cathode for urea electrolysis, only 1.44 V is required at 10 mA cm−2, which is much lower than the 1.53 V needed for overall water splitting. [ABSTRACT FROM AUTHOR]

The Mott-Schottky heterojunction of Se/NiSe 2 as electrocatalyst not only offers an extraordinary energy saving pathway for alkaline seawater splitting coupled with urea oxidation but also avoid corrosive chlorine evolution reaction at anode. [Display omitted] • The present work proposes an energy efficient strategy of seawater splitting by coupling with urea decomposition. • Se/NiSe2 Mott-Schottky heterojunction as electrocatalyst is beneficial in this regard allowing interfacial charge transfer. • The electrocatalyst offered saving of energy by 314 mV at 100 mA cm−2 in urea containing alkaline seawater. • The urea-assisted pathway for seawater splitting is found to be very sustainable process over 50 h long run at 100 mA cm−2. Seawater electrolysis is considered to be very challenging owing to competitive reaction kinetics in between oxygen evolution reaction and corrosive chlorine evolution reaction mechanism at anode, especially towards higher current density. The present work, proposes a promising and energy efficient strategy by coupling seawater splitting with urea decomposition lowering oxidation potential and thereby avoiding hypochlorite formation even at high current density. The rational design of Mott-Schottky heterojunction of Se/NiSe 2 as electrocatalyst is considered to be highly effective in this regard. The developed Se/NiSe 2 exhibits extraordinary energy saving for alkaline seawater splitting in presence of urea. The Se/NiSe 2 /NF || Se/NiSe 2 /NF electrolyser configuration achieved 10 and 50 mAcm−2 current densities with cell voltage of 1.59 and 1.70 V along with outstanding operational durability over 50 h. The large number of carrier density generates by synergistic self-driven electron transfer from Se to NiSe 2 at the heterojunction, unique metallic properties of selenium (Se), and also abundance accessible reactive edges on the porous channel of Ni foam are believed to be the reason behind such enhanced electrocatalytic activities towards urea oxidation reaction and hydrogen evolution reaction offering unique and much energy saving approach for alkaline-urea-seawater electrolysis avoiding hypochlorite formation. [ABSTRACT FROM AUTHOR]

The Ce doped Co 3 O 4 material shows excellent oxidation properties of water (overpotential of 320 mV@ 50 mA cm−2) and urea (potential of 1.39 V@ 50 mA cm−2). [Display omitted] Electrocatalytic water splitting has become one of the most promising and effective ways to solve energy crises and environmental pollution. In this work, a series of M-doped Co 3 O 4 materials with foreign ions (M = Ce, Ni and Fe) were grown on a Ni foam substrate through classical hydrothermal and calcination methods. It is worth noting that not all doping of foreign ions can promote the electrocatalytic performance of intrinsic materials. The Ce-doped Co 3 O 4 material shows excellent oxidation properties of water (overpotential of 320 mV at 50 mA cm−2) and urea (potential of 1.39 V at 50 mA cm−2). However, the doping of Ni reduces the water oxidation performance of the intrinsic material (overpotential of 410 mV@ 50 mA cm−2), and the doping of Fe reduces the urea oxidation performance of the inherent material (potential of 1.45 V@ 50 mA cm−2). A series of experimental results indicate that the improved activity of the Ce-Co 3 O 4 electrode is attributed to faster electron transport capacity, higher exposure to active sites, and improved conductivity due to doping of Ce. It is noteworthy that the doping of these ions does alter the rate-determination step for the water oxidation reaction. The stability test demonstrated that the current density of water oxidation and urea oxidation of the catalyst had no significant attenuation after a long electrocatalytic activity test. This work provides a new idea for improving the electrocatalytic activity of catalysts by a doping strategy. [ABSTRACT FROM AUTHOR]

Amorphous chromium oxide confined Ni/NiO nanoparticles-assembled nanosheets are designed for highly efficient and stable overall urea splitting. [Display omitted] Applications of urea oxidation reaction (UOR) in various sustainable energy-conversion systems are greatly hindered by its slow kinetics. Herein, we demonstrate an in - situ confined synthesis method that produces amorphous chromium oxide confined Ni/NiO nanoparticles-assembled nanosheets (Ni/NiO@CrO x) with fast reaction kinetics towards UOR. The confinement effect of the in - situ generated CrO x overlay contributes to ultrafine Ni/NiO nanoparticles, bringing about rich Ni/NiO and NiO/CrO x interfaces. In - situ Raman and electrochemical characterization show that both CrO x and metallic Ni can promote the formation of the NiOOH species and the electron transfer, leading to high intrinsic activity and fast reaction kinetics. At 1.40 V vs. reversible hydrogen electrode, the Ni/NiO@CrO x delivers a current density of 275 mA cm−2, which is about 2.6 and 6.1 times as large as those of the NiO@CrO x and NiO, respectively. In addition, the protective effect of the CrO x overlay leads to robust working stability towards UOR. Further, the Ni/NiO@CrO x nanosheets are used as bifunctional catalysts for overall urea splitting, and a small electrolysis cell voltage of 1.44 V is needed to reach the benchmark current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

A novel MOF-assisted in - situ synthetic strategy is developed to fabricate NiOOH-rich bimetallic catalysts for highly efficient urea oxidation reaction. [Display omitted] NiOOH has been considered as the active center for urea oxidation reaction (UOR), but it remains challenging to synthesize high-performance NiOOH-based catalysts. Herein, we realize the synthesis of a high-performance NiOOH-based catalyst through in - situ transformation from the NiMn-based metal–organic framework to NiMnOOH. X-ray photoelectron spectroscopy characterization shows that the Ni3+/Ni2+ ratio in the NiMnOOH is 3.9 times as big as that in the Ni(OH) 2 , and in - situ Raman characterization further consolidates the presence of the NiOOH species in the NiMnOOH and as well unveils the faciliated Ni2+/Ni3+ redox reaction. The abundant NiOOH species, the markedly facilitated Ni2+/Ni3+ redox reaction and the Ni-Mn synergy contribute to the high intrinsic activity of the NiMnOOH towards UOR. The NiMnOOH exhibits an impressively low onset potential of 1.305 V vs reversible hydrogen electrode (RHE) and requires only a small potential of 1.34 V vs RHE to deliver a current density of 100 mA cm−2 in 1.0 M KOH + 0.33 M urea. In addition, the NiMnOOH catalyst possesses good long-term working stability. [ABSTRACT FROM AUTHOR]

The Ni/NiMoO x can be successfully used as both anodic and cathodic electrodes to construct hybrid water splitting system by employing UOR to replace sluggish OER for H 2 generation. [Display omitted] • The Ni/NiMoO x was reconstructed from NiMoO 4 precursor under H 2 /Ar atmosphere. • The Ni/NiMoO x exhibits superior electrocatalytic activities toward UOR, OER, and HER. • The Ni/NiMoO x is employed to assemble a hybrid water splitting cell as both cathode and anode. • DFT results prove that the heterojunction effectively modulates the surface polarization of Ni/NiMoO x , improving its activity for UOR. Electrocatalytic urea oxidation (UOR) has attracted significant interest as a promising anodic half-reaction to replace sluggish oxygen evolution reaction (OER) toward water splitting. However, the activation and decomposition of urea molecule maintains a challenge during electrocatalytic process because of its 6e− oxidation procedure. Herein, Ni nanoparticles decorated NiMoO x nanorod (Ni/NiMoO x) electrocatalyst with abundant heterojunction interfaces is fabricated and the density functional theory (DFT) calculation testifies that the interfaces are favorable for enhancing the conductivity and modulating the surface polarization of Ni/NiMoO x , thus improving its UOR's activity. The Ni/NiMoO x performs superb electrocatalytic capacities toward UOR with a potential of 1.355 V (vs RHE) at 20 mA cm−2, and HER with an overpotential of 98 mV at 10 mA cm−2. A hybrid two-electrode water splitting cell is further assembled via applying the Ni/NiMoO x as both anodic and cathodic electrodes with presence of 0.33 M urea, delivering 50 mA cm−2 at voltage of 1.589 V. The findings help to provide a reliable strategy for rational reconstruction of Ni based metal oxide with rich interfaces for diverse electrocatalytic reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] It is urgent to develop non-noble metal electrocatalysts with both excellent activity and durable stability for H 2 production via water electrolysis. Electric energy is mainly consumed by the sluggish anodic oxygen evolution reaction (OER). The electrocatalytic urea oxidation reaction (UOR) has been regarded as a promising reaction to replace OER because of its small thermodynamic oxidation potential. However, developing a facile and large-scale preparation method for bifunctional hydrogen evolution reaction (HER) and UOR electrocatalysts is still challenging. Herein, phosphate-modified (4.46 atomic%) NiMoO 4−x net-like nanostructures are formed on Ni foam (NF) via H 3 PMo 12 O 40 etching strategy at room temperature (denoted as NF/P-NiMoO 4−x). The etched NF can directly serve as HER electrode, and delivers overpotential of 116 mV at current density of 10 mA/cm2 with Tafel slope of 77.5 mV/dec. Furthermore, it displays excellent UOR activity with potential of 1.359 V at current density of 10 mA/cm2 and Tafel slope of 19.3 mV/dec. The apparent activation energy of NF/P-NiMoO 4−x is 20.6 kJ/mol, lower than that of NF (37.7 kJ/mol), indicating smaller apparent barrier for C N bond cleavage in urea. The cell voltage of urea electrolysis is around 1.48 V for H 2 production to deliver current density of 10 mA/cm2, and better long-term stability for 50 h than that of Ir/C||Pt/C. The etching solution can be recycled for five times by addition of H 2 O 2 , turning heteropoly blue into its original state. This work develops a facile and large-scale method to prepare bifunctional HER and UOR electrocatalysts for H 2 production in a less-energy saving way via urea electrolysis. [ABSTRACT FROM AUTHOR]

Photocatalysis and photoelectrocatalysis, as green and low-cost pollutant treatment technologies, have been widely used to simultaneously degrade pollutants and produce clean energy to solve the problems of environmental pollution and energy crisis. However, the disadvantages of photocatalysts in a narrow absorption range and low utilization rate of solar energy still hinder the practical application. Here we fabricate two-dimensional porous Ruddlensden–Popper type nickel-based perovskite oxide La2NiO4 as a noble metal-free photoanode for photoelectrocatalytic urea oxidation under full spectrum sunlight irradiation. The transient photocurrent density under near infrared (NIR) light (λ > 800 nm) can reach 50 μA cm−2. Urea wastewater was used as the fuel to obtain low-energy hydrogen production, and round-the-clock hydrogen production was achieved with the optimal yield of 22.76 μmol cm−2 h−1. Moreover, a photocatalytic urea fuel cell (PUFC) was constructed with La2NiO4 as the photoanode. The power density under UV-vis-NIR was 0.575 μW cm−2. Surprisingly, the filling factor (FF) under NIR light was 0.477, which was much higher than those under UV-vis-NIR and visible light. The results demonstrated that PUFCs constructed from low-cost nickel-based perovskite oxides have potential applications for low-energy hydrogen production and efficient utilization of sunlight. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrocatalytic urea oxidation reaction (UOR) is a prospective method to substitute the slow oxygen evolution reaction (OER) and solve the problem of urea-rich water pollution due to the low thermodynamic voltage, but its complex six-electron oxidation process greatly impedes the overall efficiency of electrolysis. Here, density functional theory (DFT) calculations imply that the metallic Ni 3 S 2 and semiconductive MoS 2 could form Mott-Schottky catalyst because of the suitable band structure. Therefore, we synthesized MoS 2 /Ni 3 S 2 electrocatalyst by a simple hydrothermal method, and studied its UOR and hydrogen evolution reaction (HER) performance. The formed MoS 2 /Ni 3 S 2 Schottky heterojunction is only required 109 and 166 mV to obtain ±10 mA cm−2 for UOR and HER, respectively, showing great bifunctional catalytic activity. Moreover, the full urea electrolysis driven by MoS 2 /Ni 3 S 2 delivers 10 and 100 mA cm−2 at a relatively low potential of 1.44 and 1.59 V. Comprehensive experiments and DFT calculations demonstrate that the MoS 2 /Ni 3 S 2 Schottky heterojunction causes self-driven charge transfer at the interface and forms built-in electric field, which is not only benefit to reduce H* adsorption energy, but also helps to adjust the absorption and directional distribution of urea molecules, thereby promoting the activity of decomposition of water and urea. This research furnishes a tactic to devise more efficient catalysts for H 2 generation and the treatment of urea-rich water pollution. [ABSTRACT FROM AUTHOR]

In this study, CoS/MnCo 2 O 4 -MnO 2 (CMM) nanocomposites were synthesised by hydrothermal + electrochemical deposition and their electrochemical properties were systematically investigated for supercapacitors and energy-saving H 2 production. As an electrode material for supercapacitor, CMM achieves a specific capacitance of 2320F g−1 at 1 A/g, and maintains a specific capacitance of 1216F g−1 at 10 A/g. It also shows good cycling stability (72.8 % capacitance retention after 8000 cycles). The aqueous asymmetric supercapacitor (CMM//AC ASC) assembled from CMM electrodes (positive) and AC electrodes (negative) exhibited high energy storage capacity (887.86F g−1 specific capacitance at a current density of 1 A/g), good rate performance and cycling stability. In addition, CMM shows excellent UOR and MOR performances energy-saving H 2 production. compared to OER (1.635 V) at 20 mA cm−2, The potentials was reduced by 213 mV for UOR and 233 mV for MOR, respectively. MMC electrodes maintain a stable catalytic current for 100h and 55h, respectively. Furthermore, As a bifunctional catalyst for both UOR (MOR) and HER, CMM exhibits excellent catalytic and stability performances.Therefore, this study shows the promising practical applications of CMM nanocomposites for energy storage and energy-saving H 2 production. [Display omitted] • CoS/MnCo 2 O 4 -MnO 2 (CMM) nanocomposites were synthesised by hydrothermal and then electrochemical deposition. • CMM achieves a specific capacitance of 2320F g−1 at 1 A g−1, and maintains a specific capacitance of 1216F g−1 at 10 A g−1. It also shows good cycling stability (72.8 % capacitance retention after 8000 cycles). • The aqueous asymmetric supercapacitor (CMM//AC ASC) assembled from CMM electrodes (positive) and AC electrodes (negative) exhibited high energy storage capacity (887.86F g−1 specific capacitance at a current density of 1 A g−1). • CMM shows excellent UOR and MOR performances energy-saving H 2 production. compared to OER (1.635 V) at 20 mA cm−2, The potentials was reduced by 213 mV for UOR and 233 mV for MOR, respectively. In this study, CoS/MnCo 2 O 4 -MnO 2 (CMM) nanocomposites were synthesized by hydrothermal and then electrochemical deposition. Their electrochemical properties were systematically investigated for supercapacitors and energy-saving H 2 production. As an electrode material for supercapacitor, CMM demonstrates a specific capacitance of 2320F g−1 at 1 A/g, and maintains a specific capacitance of 1216F g−1 at 10 A/g. It also shows 72.8 % capacitance retention after 8000 cycles. The aqueous asymmetric supercapacitor exhibited high energy storage capacity (887.86F g−1 specific capacitance at a current density of 1 A/g), good rate performance and cycling stability. Besides, CMM shows outstanding urea oxidation reaction(UOR) and glycol oxidation reaction (MOR) performances for H 2 production. Compared to oxygen evolution reaction (OER) (1.635 V) at 20 mA cm−2, the potentials were reduced by 213 mV for UOR and 233 mV for MOR, respectively. Therefore, this study shows the promising practical applications of CMM nanocomposites for energy storage and energy-saving H 2 production. [ABSTRACT FROM AUTHOR]

Urea oxidation reaction (UOR) with a low equilibrium potential offers a promising route to replace the oxygen evolution reaction for energy‐saving hydrogen generation. However, the overpotential of the UOR is still high due to the complicated 6e− transfer process and adsorption/desorption of intermediate products. Herein, utilizing a cation exchange strategy, Ni‐doped CuO nanoarrays grown on 3D Cu foam are synthesized. Notably, Ni‐CuO NAs/CF requires a low potential of 1.366 V versus a reversible hydrogen electrode to drive a current density of 100 mA cm−2, outperforming various benchmark electrocatalysts and maintaining robust stability in alkaline media. Theoretical and experimental studies reveal that Ni as the driving force center can effectively enhance the urea adsorption and stabilize CO*/NH* intermediates toward the UOR. These findings suggest a new direction for constructing nanostructures and modulating electronic structures, ultimately developing promising Cu‐based electrode catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Substituting water oxidation half of water splitting with anodic oxidation of urea can reduce the cost of H 2 production and provide an avenue for treating urea-rich wastewater. However, developing an efficient and stable electrocatalyst is necessary to overcome the indolent kinetics of the urea oxidation reaction (UOR). Accordingly, we have used the Schikorr reaction to deposit Fe 3 O 4 particles on the nickel foam (Fe 3 O 4 /NF). Results from the various analysis indicated that under the operational conditions, Fe 3 O 4 underwent surface reconstruction to produce a heterolayered structure wherein a catalytically active FeOOH layer encased a conducting Fe 3 O 4. Fe 3 O 4 /NF outperformed RuO 2 as a UOR catalyst and delivered a current density of 10 50 and 100 mA cm−2 at low applied potentials of 1.38 1.42 and 1.46 V, respectively, with a Tafel slope of 28 mV dec−1. At the applied potential of 1.4 V, Fe 3 O 4 /NF demonstrated a turnover frequency (TOF) of 2.8 × 10−3 s−1, highlighting its superior intrinsic activity. In addition, a symmetrical urea electrolyzer constructed using Fe 3 O 4 /NF produced the current density of 10 mA cm−2 at a cell voltage of 1.54 V. [ABSTRACT FROM AUTHOR]

The pursuit of efficient and stable urea oxidation reaction (UOR) electrocatalysts is paramount for the sustainable utilization of renewable energy sources and the treatment of wastewater with urea content. This research introduces the successful fabrication of (Fe 0.5 Ni 0.5 ) 0.96 S/Co 9 S 8 /NF mesh heterojunction materials, which are replete with interfaces that facilitate enhanced catalytic activity. Benefiting from the electron transfer behavior from (Fe 0.5 Ni 0.5 ) 0.96 S to Co 9 S 8 , and the promotion of surface adsorption of SO 4 2- , the (Fe 0.5 Ni 0.5 ) 0.96 S/Co 9 S 8 /NF electrocatalyst has excellent UOR catalytic performance. The experimental characterization and theoretical simulation show that the d-band center/thermodynamic barrier of (Fe 0.5 Ni 0.5 ) 0.96 S/Co 9 S 8 /NF is regulated by the redistribution of electrons at the heterojunction interface, and the adsorption of SO 4 2- on the surface. The reaction barrier of the adsorption strength/rate-controlling step of urea and reaction intermediates is optimized, which promotes the catalytic kinetics and thermodynamics of UOR, offering a promising strategy for advancing energy and environmental technologies., (© 2025 Wiley‐VCH GmbH.)

Constructing built-in electric field (BIEF) in heterojunction catalyst is an effective way to optimize adsorption/desorption of reaction intermediates, while its precise tailor to achieve efficient bifunctional electrocatalysis remains great challenge. Herein, the hollow Mo/MoS Vn nanoreactors with tunable BIEFs are elaborately prepared to simultaneously promote hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) for sustainable hydrogen production. The BIEF induced by sulfur vacancies can be modulated from 0.79 to 0.57 to 0.42 mV nm -1 , and exhibits a parabola-shaped relationship with HER and UOR activities, the Mo/MoS V1 nanoreactor with moderate BIEF presents the best bifunctional activity. Theoretical calculations reveal that the moderate BIEF can evidently facilitate the hydrogen adsorption/desorption in the HER and the breakage of N─H bond in the UOR. The electrolyzer assembled with Mo/MoS V1 delivers a cell voltage of 1.49 V at 100 mA cm -2 , which is 437 mV lower than that of traditional water electrolysis, and also presents excellent durability at 200 mA cm -2 for 200 h. Life cycle assessment indicates the HER||UOR system possesses notable superiority across various environment impact and energy consumption. This work can provide theoretical and experimental direction on the rational design of advanced materials for energy-saving and eco-friendly hydrogen production., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

The catalytic activities of the Fe-N-C single-atom catalysts (SACs) are associated with the varying atomic interactions through its characteristic coordination geometry. Yet, modulation of the surface curvature of carbon acting as a supporting body has not been investigated. Herein, we report the superior catalytic activity, for both the oxygen reduction reaction (ORR) and urea oxidation reaction (UOR), of single Fe atoms anchored on a highly curved N-doped carbon dodecahedron with concave morphology (Fe SA/NhcC). Theoretical calculations and in situ spectroscopy disclose that the curvature of the carbon support helps to shorten the bond length of Fe-N, spatially redistributing the charges around the Fe and thereby lowering the d-band center toward an optimal adsorption for oxygenated species. The Fe SA/NhcC catalyst displays an ultrahigh half-wave potential of 0.926 V for ORR and a small potential difference of 0.686 V for bifunctional ORR/UOR. A rechargeable Zn-urea-air battery with the Fe SA/NhcC cathode displays robust discharge durability, excellent cycling lifespan and higher energy efficiency compared to conventional Zn-air batteries. This work provides new insight into promoting the catalytic activity of SACs through varying the surface curvature of the supporting carbon, tailoring geometric configuration and electronic states of SACs., (© 2025 Wiley‐VCH GmbH.)

The photoelectrochemical (PEC) urea oxidation reaction (UOR) presents a promising half-reaction for green hydrogen production, but the stable resonance structure of the urea molecule results in sluggish kinetics for breaking the C-N bond. Herein, we realize the record PEC UOR performance on a NiO-modified n-Si photoanode (NiO@Ni/n-Si) by harnessing the adsorbate-adsorbate interaction. We quantificationally unveil a dependence of the UOR activation barrier on the coverage of photogenerated surface high-valent Ni-oxo species (Ni IV =O) by employing operando PEC spectroscopic measurements and theoretical simulations. The strong attraction between Ni IV =O and adsorbed urea facilitates their N-O coupling while weakening the C-N bonding within urea, manifesting as the decreased UOR activation energy from 0.74 to 0.41 eV when the surface coverage of Ni IV =O is enhanced from zero to full, corresponding to more than two orders of magnitude enhancement for the UOR rate. Furthermore, an industrial-grade photocurrent density of 100 mA cm -2 is achieved at a potential as low as 1.08 V RHE by stimulating the Ni IV =O accumulation under 10 Suns, which is 300 mV lower than the potential required for most reported electrochemical counterparts. This work opens new prospects for achieving high-performance PEC urea oxidation via adsorbate-adsorbate interaction., (© 2025 Wiley-VCH GmbH.)

Nickel hydroxide (Ni(OH) 2 ) is considered to be one of the most promising electrocatalysts for urea oxidation reaction (UOR) under alkaline conditions due to its flexible structure, wide composition and abundant 3D electrons. However, its slow electrochemical reaction rate, high affinity for the reaction intermediate *COOH, easy exposure to low exponential crystal faces and limited metal active sites that seriously hinder the further improvement of UOR activities. Herein it is reported electrocatalyst composed of rich oxygen-vacancy (O v ) defects with amorphous SeO x -covered Ni(OH) 2 (O v -SeO x /Ni(OH) 2 ). Surprisingly, at 100 mA cm -2 , compared with Ni(OH) 2 (1.46 V (vs RHE)), O v -SeO x /Ni(OH) 2 has a potential of 1.35 V. Meanwhile, O v -SeO x /Ni(OH) 2 catalyst also showed good hydrogen evolution reaction (HER) performance, so it is used as the electrolytic cell assembled by UOR and HER bifunctional catalysts and only 1.57 V could reach 100 mA cm -2 . Density functional theory (DFT) study revealed that introduce of amorphous SeO x optimizes the electronic structure of the central active metal, amorphous/crystalline interfaces promote charge-carrier transfer, shift d-band center and entail numerous spin-polarized electrons during the reaction, which speeds up the UOR reaction kinetics., (© 2025 Wiley‐VCH GmbH.)

Hydrogen can be produced by electrolyzing urea aqueous solution under smaller overpotentials, owing to the lower thermodynamic potential of urea oxidation reaction (UOR) at anode than oxygen evolution reaction (OER). The efficient and selective electrocatalysts for UOR are crucial to achieve this. Herein, two NiS-based NiS/Ni 3 S 2 and NiS/NiS 2 heterojunctions with Ni cores embedding in nitrogen-doped carbon nanotubes (NiS/Ni 3 S 2 - and NiS/NiS 2 -Ni@NCNT) are demonstrated as efficient UOR electrocatalysts. The electrocatalytic UOR performance over heterojunctions is efficiently tuned by altering the electron transfer direction on their interfaces. NiS/Ni 3 S 2 -Ni@NCNT with interface electrons transferring from Ni 3 S 2 to NiS, delivers a 10 mA cm -2 UOR current density in 1.0 m KOH with 0.5 m urea at 1.37 V, superior to NiS/NiS 2 -Ni@NCNT with the electron transfer direction from NiS to NiS 2 . Experimental and theoretical calculation results reveal that NiS/Ni 3 S 2 Mott-Schottky heterojunctions facilitate the rapid in situ formation of NiOOH active species by removing electrons of Ni 3 S 2 , and also accelerate the adsorption and conversion of urea molecules and key intermediates of * CON 2 at its interfaces. This work demonstrates an interface electron transfer direction tuning strategy on heterojunctions for harvesting high-performance UOR electrocatalysts., (© 2024 Wiley‐VCH GmbH.)

The creation of highly efficient and economical electrocatalysts is essential to the massive electrolysis of water to produce clean energy. The ability to use urea reaction of oxidation (UOR) in place of the oxygen/hydrogen evolution process (OER/HER) during water splitting is a significant step toward the production of high-purity hydrogen with less energy usage. Empirical evidence suggests that the UOR process consists of two stages. First, the metal sites undergo an electrochemical pre-oxidation reaction, and then the urea molecules on the high-valence metal sites are chemically oxidized. Here, the use of scandium-doped CoTe supported on carbon nanotubes called Sc@CoTe/CNT is reported and CoTe/CNT as a composite to efficiently promote hydrogen generation from highly durable and active electrocatalysts for the OER/UOR/HER in urea and alkali solutions. Electrochemical impedance spectroscopy indicates that the UOR facilitates charge transfer across the interface. Furthermore, the Sc@CoTe/CNT nanocatalyst has high performance in KOH and KOH-containing urea solutions as demonstrated by the HER, OER, and UOR (215 mV, 1.59, and 1.31 V, respectively, at 10 mA cm -2 in 1 m KOH) and CoTe/CNT shows 195 mV, 1.61 and 1.3 V, respectively. Consequently, the total urea splitting system achieves 1.29 V, whereas the overall water splitting device obtaines 1.49 V of Sc@CoTe/CNT and CoTe/CNT shows 1.54, 1.48 V, respectively. This work presents a viable method of combining HER with UOR for maximally effective hydrogen production., (© 2024 Wiley‐VCH GmbH.)

Investigating advanced electrocatalysts is crucial for improving the efficacy of water splitting to generate environmentally friendly fuel. The discovery of highly effective electrocatalysts, capable of driving oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in urea-alkaline environments, is pivotal for advancing large-scale hydrogen production. This study aims to introduce a new method that involves creating nanosheets of high-loading iridium single atoms embedded in a manganese-containing nickel oxyhydroxide matrix (Ir@Mn─NiOOH). These nanostructures are derived from self-supported hydrate pre-catalyst nanosheets grown on nickel foam and then activated through electrochemical etching pretreatment. The Ir@Mn─NiOOH nanoarchitecture displays outstanding electrocatalytic activity, having a low overpotential of just 258 mV and a potential of 1.319 V (at 10 mA cm -2 ) for OER and UOR, respectively. Such extraordinary catalytic characteristics of Ir@Mn─NiOOH is mainly owing to the strong synthetic electronic interaction between Ir single atoms and Mn─NiOOH, which can change its electronic characteristics and boost electrochemical catalytic sites. This research presents a new way to produce exceptionally efficient catalysts by adding a synergistic effect to complex multi-electron processes., (© 2024 Wiley‐VCH GmbH.)

Water electrolysis using renewable energy is considered as a promising technique for sustainable and green hydrogen production. Conventional water electrolysis has two components - hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occurring at the cathode and anode respectively. However, electrolysis of water suffers from high overpotential due to the slow kinetics of OER. To overcome this hybrid water electrolysis has been developed by replacing conventional anode oxidation producing oxygen with oxidation of cost-effective materials producing value-added chemicals. This review summarizes recent advances in organic oxidative reactions such as alcohols, urea, hydrazine, and biomass at the anode instead of OER. Furthermore, the review also highlights the use of membrane-free hybrid water electrolysis as a method to overcome the cost and complexity associated with conventional membrane-based electrolyzer thereby improving overall efficiency. This approach holds promise for scalable and cost-effective large-scale hydrogen production along with value-added products. Finally, current challenges and future perspectives are discussed for further development in membrane-free hybrid water electrolysis., (© 2024 Wiley‐VCH GmbH.)

Urea is an essential molecule for life and the environment. In particular, in biological fluids, the urea concentration can be indicative of several pathologies. Herein, we propose a photoelectrochemical system activated by infrared irradiation (850 nm) for the detection of urea. Our sensor is made of a photoactive Si photoanode protected by a silicon oxide/Ni thin film and is coated with a Ni–Mo–O film that catalyzes the urea oxidation reaction. This approach is employed for the sensitive quantification of urea, and the operation of the system in a wide range of concentrations (from μM to 10 mM) is demonstrated, revealing a sub-μM limit of detection. Sensing is performed at a constant potential of 0.24 V vs Hg/HgO under infrared illumination, and the photocurrent output depends on the urea concentration. This new device has good reliability for urea analysis in alkaline aqueous solutions. The method is tested in the determination of the urea concentration in human urine samples, and the results are compared with a reference enzymatic photochemistry assay. The method is promising for the analysis of urine samples and can open new doors in biosensing and environmental analysis.

[Display omitted] Exploring highly efficient, robust, and stable catalysts for urea electrolysis is intensively desirable for hydrogen production but remains a challenging task. In this work, novel, well-aligned, self-supported NiS/Ni 3 S 4 heteronanorod arrays deposited on graphitized carbonized wood (GCW) are designed (denoted as NiS/Ni 3 S 4 /GCW) and synthesized by a facile hydrothermal sulfidation strategy. Benefitting from the optimized surface hydrophilicity/aerophobicity, enhanced electrical conductivity, and 3D hierarchical directional porous architectures, the NiS/Ni 3 S 4 /GCW show excellent activity toward the urea oxidation reaction and hydrogen evolution reaction in alkaline electrolytes. The arrays achieved a low potential of 1.33 V (vs. RHE) and 91 mV (overpotential) at 10 mA cm−2 as well as robust stability for 100 h. Significantly, when employed as anode and cathode simultaneously, the urea electrolyzer constructed by NiS/Ni 3 S 4 /GCW catalysts merely requires a low voltage of 1.44 V to drive 10 mA cm−2 with superior stability for 50 h. This work not only demonstrates the application of heterogeneous sulfide for urea-assisted hydrogen production but also provides an effective guideline for using renewable wood for designing efficient catalysts in an economical way. [ABSTRACT FROM AUTHOR]

[Display omitted] • A milder strategy for converting MOF into Mn-Ni(OH) 2 porous nanowire arrays is developed. • The porous nanowire arrays afford abundant spaces/channels to facilitate the active sites exposure and electron/mass transfer. • The Mn doping can modulate the electronic structural configuration of Ni(OH) 2. • Mn-Ni(OH) 2 PNAs exhibited superior activity and robust durability toward UOR. Replacement of the sluggish anodic reaction in water electrocatalysis by a thermodynamically favorable urea oxidation reaction (UOR) offers the prospect of energy-saving H 2 generation, additionally mitigating urea-rich wastewater pollution, whereas the lack of highly efficient and earth-abundant UOR catalysts severely restricts widespread use of this catalytic system. Herein, Mn-doped nickel hydroxide porous nanowire arrays (denoted Mn-Ni(OH) 2 PNAs) are rationally developed and evaluated as efficient catalysts for the UOR in an alkaline solution via the in situ electrochemical conversion of NiMn-based metal–organic frameworks. Mn doping can modulate the electronic structural configuration of Ni(OH) 2 to significantly increase the electron density and optimize the energy barriers of the CO*/NH 2 * intermediates of the UOR. Meanwhile, porous nanowire arrays will afford abundant spaces/channels to facilitate active site exposure and electron/mass transfer. As a result, the Mn-Ni(OH) 2 PNAs delivered superior UOR performance with a small potential of 1.37 V vs. RHE at 50 mA cm−2, a Tafel slope of 31 mV dec-1, and robust stability. Notably, the overall urea electrolysis system coupled with a commercial Pt/C cathode demonstrated excellent activity (1.40 V at 20 mA cm−2) and durability operation (only 1.40% decay after 48 h). [ABSTRACT FROM AUTHOR]

[Display omitted] Urea electrooxidation with favorable thermodynamic potential is highly anticipated but suffering from sluggish kinetics. Deciphering the activity origin and achieving rational structure design are pivotal for developing highly efficient electrocatalyst for urea oxidation reaction (UOR). Herein, nitrogen penetrated nickel nanoparticles confined in carbon nanotubes (Ni-NCNT) is successfully achieved to drive UOR. Active origin of Ni-NCNT is decoded to be the in-situ generated Ni2+δO(OH) ads according to comprehensive analysis. The electrophilic Ni2+δ and protophilic OH ads could targeted capture O and H atoms from urea, respectively, achieving molecule activation and accelerating the subsequent proton coupled electron transfer reactions. Nitrogen penetration is identified to promote prior formation of Ni2+δO(OH) ads and push up the d band center of Ni-NCNT, enhancing urea adsorption and subsequent molecule cleavage reactions. As a result, Ni-NCNT exhibits superior UOR performance. This work supplies valuable insights for the rational design and construction of efficient nickel-based catalyst for driving UOR. [ABSTRACT FROM AUTHOR]

The development of high-performance, low-cost, and non-noble metal catalysts for the urea oxidation reaction (UOR) as an alternative to oxygen evolution reaction (OER) has received much attention but remains a huge challenge. In this work, NiSe 2 /TiN@Ni 12 P 5 /NF catalysts with a stalactite structure were prepared by chemical vapor deposition to obtain the integrated electrode Ni 12 P 5 /NF on the nickel foam (NF), and subsequently NiSe 2 /TiN was formed on the Ni 12 P 5 /NF surface by the hydrothermal method. The designed catalyst delivers an ultra-low potential of 1.270 V at 10 mA cm−2, and a Tafel slope of 33.3 mV dec−1 for UOR. Furthermore, the catalyst only shows a 1.7% decrease in potential after an 80-h stability test, which demonstrates its excellent stability. The prepared NiSe 2 /TiN@Ni 12 P 5 /NF shows a high specific surface area, and the strengthening effect between TiN and NiSe 2 , endowing the catalyst a high activity and durability. [Display omitted] • The NiSe 2 /TiN@Ni 12 P 5 /NF catalyst with stalactite structure is prepared by the hydrothermal method. • The TiN as the second phase particle combines with NiSe 2 to form a catalyst with a dispersion strengthening effect. • The NiSe 2 /TiN@Ni 12 P 5 /NF catalyst indicates that the ultra-low potential of UOR is 1.270 V at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

[Display omitted] Constructing heterostructure is an efficient method to provide more active sites and optimize electronic structure for improving the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) performance. Herein, the 3D FeOOH@Co 3 O 4 heterostructure was constructed using FeOOH layer (10–20 nm) coated on the surface of Co 3 O 4 nanoneedles through the strong hydrolysis of Fe3+. The FeOOH@Co 3 O 4 heterostructure not only retains the nanoneedle structure with open frameworks, but also improves the specific surface area and expedites the charge transfer. The FeOOH@Co 3 O 4 -240 heterostructure affords a remarkable OER performance with low overpotential of 228 mV at 10 mA·cm−2 in 1 M KOH solution. The symmetrical urea electrolyzer using FeOOH@Co 3 O 4 -240 as both anode and cathode delivers 10 mA/cm2 at 1.43 V. Density functional theory (DFT) calculations unveil that the FeOOH@Co 3 O 4 -240 heterostructure could adjust the electronic structure and strengthen the conductivity. This work offered a facile strategy for designing heterojunction catalysts in an economic way. [ABSTRACT FROM AUTHOR]

The anode oxygen evolution reaction (OER) is a delayed half-reaction of water splitting that requires a relatively high overpotential. Therefore, a more easily oxidized urea oxidation reaction (UOR) has been implemented to replace OER. Co–Mo-based bimetallic oxides have been recognized as interesting candidates for electrocatalytic water splitting due to their unique d electron configurations, but the low conductivity and limited active sites still hinder their development. Herein, we demonstrated that anion-modulation in CoMoO 4 nanoplates as coupled hydrogen evolution reaction (HER) and UOR for convenient and efficient urea-assisted hydrogen-production system are demonstrated. The findings of the experiments show that nitrogen doping and phosphorus doping exhibit excellent activity toward alkaline HER and UOR, respectively. As a result, the N–CoMoO 4 and P–CoMoO 4 electrode exhibit low potentials of −0.062 V and 1.251 V (vs. RHE) to reach a current of 10 mA cm−2 for HER and UOR. The full urea electrolysis is driven by N–CoMoO 4 ||P–CoMoO 4 executes stably for 24 h at a low potential of 1.41 V. This is a unique anion-modulation method in electrocatalysts to combine hydrogen generation and sewage treatment, which could pave the way for the creation of long-term energy conversion systems. [Display omitted] • Modification of bimetallic oxides using anionic regulation strategies. • The incorporation of nitrogen and phosphorus ions encourages HER and UOR, respectively. • The electrocatalyst presents a low potential of 1.251 V at 10 mA cm−2 for UOR. • The full urea electrolysis delivered the current density of 10 mA cm−2 at 1.41 V for 24 h. [ABSTRACT FROM AUTHOR]

Summary: In this work, SnS/SnS2 heterostructured film on a nickel foam (NF) through solution process was grown and employed directly as cathode and anode to the urea oxidation reaction (UOR). The as‐fabricated SnS/SnS2 film achieves high efficiency toward UOR with a lower potential of 1.38 V vs RHE to deliver 50 mA cm−2, which is approximately 200 mV less than the potential demanded for the oxygen evolution reaction (OER). More importantly, the electrolyzer consisting of two identical electrodes with the SnS/SnS2/NF ǁ SnS/SnS2/NF vs RHE assembly oxidizes urea at a lower potential of 1.36, 1.38, and 1.39 V vs RHE to deliver a current density of 10, 50, and 100 mAcm−2, respectively. The superior UOR performance of the SnS/SnS2‐based electrode is attributed to the combined merits of the SnS and SnS2 phases in the heterostructure, enhancing the catalytic active sites and providing the easy charge transport between the electrode and electrolyte. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is a sustainable and feasible strategy for hydrogen production but is hampered by the sluggish anodic oxygen evolution reaction (OER). Herein, an effective approach is introduced to significantly decrease the cell voltage by replacing the anodic OER with a urea oxidation reaction (UOR). A Ni2P/NiMoP nanosheet catalyst with a hierarchical architecture is uniformly grown on a nickel foam (NF) substrate through a simple hydrothermal and phosphorization method. The Ni2P/NiMoP achieves impressive HER activity, with a low overpotential of only 22 mV at 10 mA cm–2 and a low Tafel slope of 34.5 mV dec–1. In addition, the oxidation voltage is significantly reduced from 1.49 V to 1.33 V after the introduction of 0.33 M urea. Notably, a two-electrode electrolyzer employing Ni2P/NiMoP as a bifunctional catalyst exhibits a current density of 10 mA cm–2 at a cell voltage of 1.35 V and excellent long-term durability after 80 h.

Developing high-performance catalysts for electrocatalytic urea oxidation reaction (UOR) is significant in treating urea-rich wastewater but remains a considerable challenge. Herein, CuNiCo-7.8 %Mo/CF (7.8 % is the Mo atom percentage; CF: copper foam) medium entropy alloy catalyst with moderate local lattice tensile strain and built-in electric field is prepared by solvothermal and calcination methods to obtain the good UOR performance. Besides, the operando electrochemical impedance and quasi-operando Raman spectroscopy proved that CuNiCo-7.8 %Mo/CF can favor the direct oxidation reaction in a solution of 1.0 M KOH and 0.5 M urea. The electrochemical results show that CuNiCo-7.8 %Mo/CF has a better UOR activity (E 10/500/1000 = 1.27/1.44/1.51 V) than other studied samples during the UOR process. Meanwhile, CuNiCo-7.8 %Mo/CF can stably work for 100 h at 1000 mA cm−2. Therefore, a CuNiCo-7.8 %Mo/CF material is designed for high-efficiency UOR at large current density and it is provided as a feasible method for large-scale treating urea-rich wastewater. [Display omitted] • Adjusting the local lattice tensile strain of CuNiCo MEA by adding Mo atoms. • Addition of Mo induces the generation of built-in electric field in the CuNiCo MEA. • The direct oxidation reaction mechanism is explored during the UOR process. • CuNiCo-7.8 %Mo/CF shows good UOR performance at ampere-level current density. [ABSTRACT FROM AUTHOR]