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Two new supramolecular photocatalysts made of covalently linked Ru(II) polypyridine chromophore subunits ([Ru(bpy)3]2+-type species; bpy = 2,2′-bipyridine) and [RuL(pic)2] (L = 2,2′-bipyridine-6,6′-dicarboxylic acid; pic = 4-picoline) water oxidation catalyst subunits have been prepared. The new species, 1 and 2, contain chromophore and catalyst subunits in the molecular ratios 1:1 and 1:2, respectively. The model chromophore species [Ru(bpy)2(L1)]2+ (RuP1; L1=4-[2-(4-pyridyl)-2-hydroxyethyl]-4-methyl-2,2′-bipyridine) and [Ru(bpy)2(L2)]2+ (RuP2; L2 = 4,4′-bis[2-(4-pyridyl)-2-hydroxyethyl]-2,2′-bipyridine) have also been prepared. The absorption spectra, oxidation behavior, and luminescent properties of 1 and 2 have been studied, and the results indicate that each subunit largely maintains its own properties in the supramolecular species. However, the luminescence of the chromophore subunits is significantly quenched in 1 and 2 in comparison with the luminescence of the respective model species. Both 1 and 2 exhibit catalytic water oxidation in the presence of cerium ammonium nitrate, exhibiting an I2M mechanism, with a better efficiency than the known catalyst [RuL(pic)2] under the same experimental conditions. Upon light irradiation, in the presence of persulfate as a sacrificial acceptor agent, 1 and 2 are more efficient photocatalysts than a system made of separated [Ru(bpy)3]2+ and [RuL(pic)2] species, highlighting the advantage of using multicomponent, supramolecular species with respect to isolated species. The O–O bond formation step is I2M, even in the photo-driven process. The photocatalytic process of 2 is more efficient than that of 1, with the turnover frequency reaching a value of 1.2 s−1. A possible reason could be an increased local concentration of catalytic subunits in the needed bimolecular assembly required for the I2M mechanism in 2 with respect to 1, a consequence of the presence of two catalytic subunits in each multicomponent species 2. [ABSTRACT FROM AUTHOR]

Understanding the protonation behavior of metal-oxo water oxidation catalysts is essential to improve catalyst efficiency and long-term performance, as well as to tune their properties for specific applications. In this work, we explore the basicity and protonation effects of the highly active water oxidation catalyst [(Mn4O4) (V4O13) (OAc)3]3− using density functional theory. We computed the relative free energies of protonation in a systematic fashion for all symmetry-inequivalent O atoms, where the presence of multiple oxidation states from Mn 4 IV to Mn 4 III and a rich Jahn–Teller isomerism adds a significant amount of complexity. For high oxidation states, the compound behaves like some other polyoxometalates, showing protonation preferably at the terminal and μ2-bridging O atoms of the vanadate cap. However, upon reduction, eventually, the protonation preference switches to the cubane O atoms, mostly driven by a strong increase in basicity for O atoms located along the Jahn–Teller axes. Our work further evidences that protonation can potentially lead to several chemical transformations, like disproportionation and charge transfer to vanadium, dissociation of ligands, or the opening of the cubane structure. Our simulated UV/Vis absorption spectra additionally provide valuable insights about how the protonation of the catalyst could be tracked experimentally. Overall, our analysis highlights the complexity involved in the protonation of heterometallic polyoxometalate clusters. [ABSTRACT FROM AUTHOR]

The sluggish oxygen evolution reaction (OER) in overall electrocatalytic water splitting poses a significant challenge in hydrogen production. A series of transition metal phosphides are emerging as promising electrocatalysts, effectively modulating the charge distribution of surrounding atoms for OER. In this study, a highly efficient OER electrocatalyst (CoP-CNR-CNT) was successfully synthesized through the pyrolysis and phosphatization of a Co-doped In-based coordination polymer, specifically InOF-25. This process resulted in evenly dispersed CoP nanoparticles encapsulated in coordination polymer-derived carbon nanoribbons. The synthesized CoP-CNR-CNT demonstrated a competitive OER activity with a smaller overpotential (η10) of 295.7 mV at 10 mA cm-2 and a satisfactory long-term stability compared to the state-of-the-art RuO2 (η10 = 353.7 mV). The high OER activity and stability can be attributed to the high conductivity of the carbon network, the abundance of CoP particles, and the intricate nanostructure of nanoribbons/nanotubes. This work provides valuable insights into the rational design and facile preparation of efficient non-precious metal-based OER electrocatalysts from inorganic–organic coordination polymers, with potential applications in various energy conversion and storage systems. [ABSTRACT FROM AUTHOR]

The development of robust and efficient photocatalytic constructs for boosting the water oxidation reaction (WOR) is needed for establishing a sunlight-driven renewable energy infrastructure. Here, we synthesized plasmonic core–shell nanoconstructs consisting of triangular gold nanoprism (AuTNP) core with mixed manganese oxide (MnOx) shell for photoelectrocatalytic WOR. These constructs show electrocatalytic WOR with a low onset overpotential requirement of 270 mV at pH 10. Photoexcitation showed further enhancement of their catalytic activity resulting in ∼15% decrease of the onset overpotential requirement along with the generation of photocurrent density of up to 300 μA/cm2. We showed that such light-driven enhancement of AuTNP@MnOx dyad's catalytic activity toward the WOR process includes contributions from both photocatalytic (hot carriers driven) and photothermal effects with photothermal effect playing the major role for wavelength between 532 and 808 nm. The contribution from the photocatalytic effect is appreciable only for high-energy excitations near the interband region, while the photothermal effect largely dominates for lower energy excitations near the LSPR wavelengths of the dyad. [ABSTRACT FROM AUTHOR]

Perovskite oxides have emerged as catalysts for electrochemical water splitting, and surface reconstruction is crucial for their electrocatalytic performance. In this study, we report the surface reconstruction of Ruddlesden–Popper-based oxides under nonreactive and electrochemical conditions. The rapid migration of Sr ions from the bulk to the surface results in a porous structure, increase the number of oxygen vacancies, and produces an A-site cation deficiency. Collectively, these modifications significantly enhance the electrocatalytic activity and stability for water oxidation. In addition, the engineered electrocatalysts have a low overpotential of 350 mV at 10 mA cm−2, alone with a Tafel slope of 77 mV dec−1. They also exhibit outstanding durability, maintaining a current density of 5 mA cm−2 over 6 h. [Display omitted] [ABSTRACT FROM AUTHOR]

Recently, tungsten oxide (WO 3) and bismuth vanadate (BiVO 4) have been considered as an intriguing combination for constructing a heterojunction for efficient photoelectrochemical (PEC) applications. Herein, we report the preparation of ternary WO 3 /BiVO 4 /NiCo layered double hydroxide (LDH) photoanodes for boosting photogenerated carrier transport and promotion of catalytic activity. WO 3 /BiVO 4 heterostructures were synthesized by a hydrothermal process of WO 3 nanoplates on a fluorine-doped tin oxide (FTO) glass substrate, followed by spin-coating for BiVO 4 materials. We investigated the effect of a NiCo LDH catalyst on PEC performance by controlling the growth temperatures of the NiCo LDH via hydrothermal synthesis. Moreover, the X-ray diffraction (XRD), Fourier‒transform infrared (FTIR) and X‒ray photoelectron spectroscopy (XPS) analyses revealed that the WO 3 /BiVO 4 heterojunction was retained after the NiCo LDH growth process regardless of synthesis temperatures. The PEC results verified that the WO 3 /BiVO 4 heterostructure with the optimized NiCo LDH catalyst (WBN60) possessed the best photocurrent density of 3.2 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), which created improved charge separation and surface oxidation kinetics of photogenerated carriers. Consequentially, the smallest charge transfer resistance and recombination rate were achieved in the WBN60 electrode compared to others, indicating a much lower photoelectrode‒electrolyte interfacial resistance and the enhancement of photogenerated carrier transport by suppressing recombination. [ABSTRACT FROM AUTHOR]

The quest for cost effective but active electrocatalysts for water oxidation is at the forefront of research towards hydrogen economy. In this regard, bamboo as biomass derived N-doped cellulosic carbon has shown potential electrocatalytic performance towards water oxidation. The impregnation of optimum metallic Fe boosts the performance further, achieving an over potential value of 238 mV at a benchmark current density of 10 mA cm-2. Owing to its promising OER performances in alkaline freshwater, the electrocatalyst was further explored in alkaline saline water and alkaline real seawater, exhibiting overpotentials of 272 mV and 280 mV, respectively, to reach 10 mA cm-2 current density. Most importantly, the protective graphitic multilayer surrounding the metallic Fe allowed the electrocatalyst to demonstrate excellent durability over 30 h even at a high current density in alkaline real seawater electrolyte. [ABSTRACT FROM AUTHOR]

Perovskite oxides are promising catalysts for water oxidation. Herein, we constructed a Sr3CoFeWO9 triple perovskite with Co, Fe, and W atoms sharing octahedral positions. Thermally activated growth of an amorphous FeCoW oxyhydroxide layer on this perovskite pre-catalyst greatly enhanced the oxygen evolution reaction (OER) activities, reducing overpotential at 10 mA cm−2geo by 115 mV. This highlights the benefits of compositional design and structural reconstruction for efficient electrocatalytic materials. [ABSTRACT FROM AUTHOR]

Spin state is often regarded as the crucial valve to release the reactivity of energy‐related catalysts, yet it is also challenging to precisely manipulate, especially for the active center ions occupied at the specific geometric sites. Herein, a π–π type orbital coupling of 3d (Co)‐2p (O)‐4f (Ce) was employed to regulate the spin state of octahedral cobalt sites (CoOh) in the composite of Co3O4/CeO2. More specifically, the equivalent high‐spin ratio of CoOh can reach to 54.7 % via tuning the CeO2 content, thereby triggering the average eg filling (1.094) close to the theoretical optimum value. The corresponding catalyst exhibits a superior water oxidation performance with an overpotential of 251 mV at 10 mA cm−2, rivaling most cobalt‐based oxides state‐of‐the‐art. The π–π type coupling corroborated by the matched energy levels between Ce t1u/t2u‐O and CoOh t2g‐O π type bond in the calculated crystal orbital Hamilton population and partial density of states profiles, stimulates a π‐donation between O 2p and π‐symmetric Ce 4fyz2 orbital, consequently facilitating the electrons hopping from t2g to eg orbital of CoOh. This work offers an in‐depth insight into understanding the 4f and 3d orbital coupling for spin state optimization in composite oxides. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of BiVO4 limits its applications in solar-to-hydrogen energy conversion. In this work, the zeolitic imidazolate framework ZIF-67 as a cocatalyst was immobilized on a BiVO4 nanocone via a solution-based photo-deposition method for photoelectrochemical water oxidation. Under the assistance of the nano-tip effect induced by the BiVO4 tip, nanoflower-like ZIF-67 was selectively grown at the vertex of the BiVO4 nanocone. The constructed BiVO4/ZIF-67 composite photoelectrode yielded a photocurrent of 0.92 mA cm−2 at ∼1.23 VRHE, which is about 3.5-fold that of pure BiVO4. In addition, surface/bulk charge separation efficiencies (ηsurf and ηbulk) were elevated when compared to those of the BiVO4 photoelectrode. Photoelectrochemical impedance spectroscopy (PEIS) and intensity modulated photocurrent spectroscopy (IMPS) measurements were further investigated to reveal the critical role of the modification of ZIF-67 in suppressing charge recombination and improving the photoelectrochemical activity of BiVO4. This research presents a feasible way to design a BiVO4/MOF composite photoanode induced by the nano-tip effect for enhanced photoelectrochemical water splitting performance. [ABSTRACT FROM AUTHOR]

Hydrogen production through electrocatalytic water splitting or urea splitting has been considered one of the most fascinating methods to relieve the energy pressure. In this paper, the effects of Zr introduction on formation of NiFe 2 O 4 and catalytic activity are studied. Using oxygen evolution and urea oxidation as concerned reactions, the effects of different dosage on the catalytic performance of the materials were performed. It was found that the Zr–NiFe LDH@NiFe 2 O 4 /NF-1 material exhibited superior water oxidation properties (overpotential of 290 mV @100 mA cm−2). For urea oxidation reaction, the catalytic performance of this NiFe LDH material is better at low current density. However, at high current densities, this Zr–NiFe LDH@NiFe 2 O 4 /NF-1 electrode exhibits better electrochemistry performance. It is proved that the oxidation of water also contributes a part of the activity under large current. Density functional theory also suggests that the NiFe 2 O 4 material is favorable for water adsorption. This work will provide novel opinion for the development of environmentally friendly and low cost materials. It was found that the Zr–NiFe LDH@NiFe 2 O 4 /NF-1 material exhibited superior water oxidation properties (overpotential of 290 mV @100 mA cm−2). [Display omitted] • The formation of this NiFe LDH and NiFe 2 O 4 material can be induced by modulating the content of Zr. • The Zr–NiFe LDH@NiFe 2 O 4 presents a improved activity with small overpotentials of 290 mV for water oxidation. • The increase of performance is ascribed to the accelerated charge transfer and promoted electrolyte transfer. [ABSTRACT FROM AUTHOR]

Progesterone (PGT) is a steroid hormone produced naturally by pregnant women. Advent of pharmaceuticals gave rise to synthetic production of PGT as a medicine for various pregnancy-related issues. As a result of synthetic production and high utilization rate of PGT, they have become an emerging contaminant in water sources worldwide. Conventional wastewater treatment is not competent enough to remove steroid contaminants. Hence, the current study attempted the degradation of 10 mg L−1 of PGT in water using photocatalysis (PC) followed by electrocatalytic oxidation (EC) using vanadium pentoxide (V2O5) and carbon-coated titanium (C/Ti) anode. Optimization studies found UV-C irradiation, pH 5, 50-mg L−1 catalyst dosage, 180-min PC followed by 300-min EC, and 69 mA cm−2 current density eliminating 96% COD and 71.5% TOC. Comparative studies showed that PC(UV-C) + EC was 50% and 25% more efficient than electrochemical oxidation and electrocatalytic oxidation for TOC removal. Photocatalytic pretreatment brought down current consumption of the process by 23 mA cm−2. High-resolution mass spectrometry (HRMS) studies were utilized to propose the degradation pathway that involved hydroxylation, demethylation, dehydroxylation, and decarboxylation mechanisms. [ABSTRACT FROM AUTHOR]

Esomeprazole (ESO) is one of the proton pump inhibitors (PPIs) that is commonly used to treat extreme acidity and gastrointestinal irritation. Since it is used at a high rate, it is now classified as a pollutant of emerging concern (CEC). ESO gravely jeopardizes the health of living beings because it persists in water and wastewater sources even after standard treatment. Studies on the effective removal of PPIs, especially ESO, are scarce. In the current study, esomeprazole is disintegrated in water using electrochemical oxidation (EO). Titanium cathode with sodium sulfate electrolyte and carbon coated titanium (C/Ti) anode were used to apply EO. Through optimization studies utilizing COD measurement, it was discovered that 93% of the COD could be removed at pH 3, 60 mM sodium sulfate concentration, 300 min treatment period, and 115 mA cm−2 current density. Whereas TOC research revealed only 44% mineralization, HPLC‐PDA experiments revealed 100% ESO transformation. High resolution mass spectrometry (HRMS) studies were used to propose a degradation mechanism and pathway. The primary processes of degradation included desulfurization, thioperoxole group formation, sulfinyl benzimidazole group breakage, and demethylation. More than 20 reuses of the anode and cathode materials were possible without significantly lowering their oxidation efficiency. [ABSTRACT FROM AUTHOR]

Solar irradiation can efficiently promote the kinetics of the oxygen evolution reaction (OER) during water splitting, where heterojunction catalysts exhibit excellent photoresponsive properties. However, insights into the origins of photoassisted OER catalysis remain unclear, especially the interfaced promotion under convergent solar irradiation (CSI). Herein, novel allotropic Co5.47N/CoN heterojunctions were synthesized, and corresponding OER mechanisms under CSI were comprehensively uncovered from physical and chemical aspects using the in situ Raman technique and electrochemical cyclic voltammetry method. Our results provide a unique mechanism where high‐energy UV light promotes the Co3+/4+ conversion process in addition to the ordinary photoelectric effect excitation of the Co2+ material. Importantly, visible light under CSI can produce a photothermal effect for Co2+ excitation and Co3+/4+ conversion, which promotes the OER significantly more than the usual photoelectric effect. As a result, Co5.47N/CoN (containing 28% CoN) obtained 317.9% OER enhancement, which provides a pathway for constructing excellent OER catalysts. [ABSTRACT FROM AUTHOR]

The development of active water oxidation catalysts for water splitting has stimulated considerable interest. Herein, the design and building of single atom Co sites using a supramolecular tailoring strategy are reported, that is, the introduction of pillar[4]arene[1]quinone (P4A1Q) permits mononuclear Co species stereoelectronically assembled on MoS2 matrix to construct an atomically dispersed MoS2@Co catalyst with modulated local electronic structure, definite chemical environment and enhanced oxygen evolution reaction performance. Theoretical calculations indicate that immsobilized single‐Co sites exhibit an optimized adsorption capability of oxygen‐containing intermediates, endowing the catalyst an excellent electrocatalytic oxygen evolution reaction activity, with a low overpotential of 370 mV at 10 mA cm−2 and a small Tafel slope of 90 mV dec−1. The extendable potential of this strategy to other electrocatalysts such as MoS2@Ni and MoS2@Zn, and other applications such as the hydrogen evolution reaction was also demonstrated. This study affords new insights into the rational design of single metal atom systems with enhanced electrocatalytic performance. [ABSTRACT FROM AUTHOR]

As a new water treatment technology, Fenton-like reaction has great potential. In this study, we successfully prepared an excellent Fenton-like catalyst, which is composed of cobalt monoatoms and asymmetric subnanoclusters (labeled CoSA/Clu-C2N), and exhibits excellent peroxymonosulfate (PMS) activation reactivity. By directly comparing the catalytic properties of CoSA-C2N and CoSA/Clu-C2N, the synergistic effects of coasymmetric Co subclusters and Co atoms on the activation of PMS and degradation of organic micropollutants were investigated. The results showed that CoSA/Clu-C2N had higher degradation rates of carbamazepine (CBZ), antipyrine (AT) and chlorobenzoic acid (CA) when combined with active oxidant PMS. The cyclic frequency of CBZ was 5.4 min−1, which was twice as high as the catalytic constant of CoSA-C2N (2.4 min−1). The results show that CoSA/Clu-C2N cobalt subnanoclusters and cobalt single atom can synergistically improve the catalytic performance of activated PMS oxidation of micropollutants in water. In addition, electron paramagnetic resonance (EPR) technology has proved that the introduction of Co subnano clusters in CoSA/Clu-C2N is conducive to the production of singlet oxygen (1O2), thereby improving the efficiency of pollutant oxidation. This work lays a solid foundation for the future design of advanced multifunctional catalysts by carefully regulating and combining monmetallic atoms and metal subnanoclusters. [ABSTRACT FROM AUTHOR]

Entropy‐based polymetallic oxides with configurational entropy, structure flexibility, and crystallographic orientation have been regarded as promising catalysts for oxygen evolution reaction (OER), due to their electronic energy band occupation, composition ligand stabilization, and “cocktail” effect. Herein, a rutile RuIrAgMnO2 oxide with an orientation along the (110) facets is first fabricated by a low‐temperature directional co‐pyrolysis strategy of metal salts on Ti foil at 300 °C. The quaternary oxide exhibits a texture coefficient of 1.13 along (110) facet, resulting from concerted shaping of Ag and Mn components presenting a vibrational entropy of 1.13 R (R is the gas content). In 0.5 m H2SO4, it displays an overpotential of 171 mV at 10 mA cm−2 for OER, running at a voltage for 340 h at 100 mA cm−2. The remarkably improved performance can be associated with the presence of the preferred (110) facets with in‐plane strains, which activate and stabilize OER process via electronic energy band reconstruction. More interestingly, the preferential orientation prevents the diffusion or dissolution of active metal ions caused by entropy‐dependent energy barriers, ensuring long‐term stability. This work can pave the way for entropy‐driven polymetallic oxides with optimal structures, disrupting the trade‐off between activity and stability in water oxidation. [ABSTRACT FROM AUTHOR]

The corrosion of SiCf/SiC composites in gas environment threatens their long‐term service in aeroengines as hot‐end structure components. Addition of corrosion‐resistant phases into SiC matrix is a potential strategy to improve the service performance of SiCf/SiC materials. Here, AlN added SiC ceramics were prepared by reactive melt infiltration, and the effect of AlN phase on the oxidation resistance of the ceramics was emphasized. The oxidation tests were performed in dry oxygen and water oxygen atmospheres at 1100°C–1300°C, respectively. The oxidation mechanism was discussed based on the microstructure evolution of the oxide layer. The results show that the oxide layer is composed of aluminum silicate glass and Al2O3 flakes dispersedly distributed in the glass phase. As the temperature rises, the oxide layer gradually grows and thickens. Finally, a smooth and dense protective layer could be formed on the surface of ceramics to resist oxidation. This study can provide a profound insight to construct SiCf/SiC composites with excellent oxidation resistance. [ABSTRACT FROM AUTHOR]

Interstitial filling of light atoms strongly affects the electronic structure and adsorption properties of the parent catalyst due to ligand and ensemble effects. Different from the conventional doping and surface modification, constructing ordered intermetallic structures is more promising to overcome the dissolution and reconstruction of active sites through strong interactions generated by atomic periodic arrangement, achieving joint improvement in catalytic activity and stability. However, for tightly arranged metal lattices, such as iridium (Ir), obtaining ordered filling atoms and further unveiling their interstitial effects are still limited by highly activated processes. Herein, we report a high‐temperature molten salt assisted strategy to form the intermetallic Ir−B compounds (IrB1.1) with ordered filling by light boron (B) atoms. The B residing in the interstitial lattice of Ir constitutes favorable adsorption surfaces through a donor‐acceptor architecture, which has an optimal free energy uphill in rate‐determining step (RDS) of oxygen evolution reaction (OER), resulting in enhanced activity. Meanwhile, the strong coupling of Ir−B structural units suppresses the demetallation and reconstruction behavior of Ir, ensuring catalytic stability. Such B‐induced interstitial effects endow IrB1.1 with higher OER performance than commercial IrO2, which is further validated in proton exchange membrane water electrolyzers (PEMWEs). [ABSTRACT FROM AUTHOR]

Integrating anodic coal gasification fine slag oxidation with cathodic hydrogen evolution reaction presents an environmentally friendly and energy-efficient solution for solid waste recycling and hydrogen production. This innovative approach exhibits higher activity and stability than conventional water electrolysis, while also preventing anode degradation due to its benign reaction conditions. The kinetic investigations have revealed that slag oxidation occurs more rapidly than water oxidation. Specifically, slag undergoes direct and indirect oxidation within the potential regions below and above those of water oxidation, respectively. This study has the potential to shed light on the mechanisms underlying slag electrolysis and offer valuable insights for the simultaneous recycling of solid waste and hydrogen production. [ABSTRACT FROM AUTHOR]

Rare earth (RE)‐based perovskites are considered as promising platform for oxygen evolution reaction (OER) due to their low cost and tunable structures. However, the systematic synthesis of perovskite catalysts with satisfactory performance has rarely been reported. Herein, a general synthetic protocol for RE‐substituted LaCoO3 (RE‐LCO) perovskites is demonstrated. Particularly, after loaded with RuO2, the as‐prepared RuO2:0.2Ce‐LCO hybrid structures exhibit OER performance with a low overpotential of 135 mV at 10 mA cm−2 in 1.0 m KOH, together with remarkable long‐term operation, representing one of the most efficient and robust Ru‐based catalysts. Comprehensive experimental results indicate that the enhanced OER mechanism is attributed to the Ce‐substitution, which alters the geometric configuration of CoO6 octahedra and generates more oxygen vacancies. Furthermore, the robust interaction between Ce‐LCO and RuO2 stabilizes the valence state of Ru site. Theoretical calculations corroborate that Co 3d orbitals overlap with Ce 4f orbitals near the Fermi level, greatly improving the electron transfer between Co and Ce atoms. [ABSTRACT FROM AUTHOR]

Stable homogeneous two‐electron water oxidation electrocatalysts are highly demanded to understand the precise mechanism and reaction intermediates of electrochemical H2O2 production. Here we report a tetranuclear manganese complex with a cubane structure which can electrocatalyze water oxidation to hydrogen peroxide under alkaline and neutral conditions. Such a complex demonstrates an optimal Faradaic efficiency (FE) of 87 %, which is amongst (if not) the highest FE(H2O2) of reported homogeneous and heterogeneous electrocatalysts. In addition, active species were identified and co‐catalysts were excluded through ESI‐MS characterization. Furthermore, we identified water binding sites and isolated one‐electron oxidation intermediate by chemical oxidation of the catalyst in the presence of water substrates. It is evident that efficient proton‐accepting electrolytes avoid rapid proton building‐up at electrode and substantially improve reaction rate and selectivity. Accordingly, we propose a two‐electron catalytic cycle model for water oxidation to hydrogen peroxide with the bioinspired molecular electrocatalyst. The present work is expected to provide an ideal platform to elucidate the two‐electron WOR mechanism at the atomic level. [ABSTRACT FROM AUTHOR]

We have successfully synthesized a new Ni(II)‐based coordination polymer (CP) [Ni2(cis‐1,4‐chdc)2(4,4′‐bpy)3(H2O)2] (1); (cis‐1,4‐ H2chdc=cis‐1,4‐cyclohexanedicarboxylic acid and 4,4′‐bpy=4,4′‐bipyridine) employing slow diffusion method in a single pot technique. The connectivity of Ni(II) ions and bridging cis‐1,4‐chdc ligand gives rise to a three‐dimensional (3D) framework with 2‐fold interpenetrated diamondoid topology. Interestingly, the synthesized CP acts as efficient catalyst for electrocatalytic water splitting. The water oxidation activity of compound 1 exhibits Tafel slope equivalent to 361.48 mV.dec−1 for hydrogen evolution reaction (HER) and 353.53 mV.dec−1 for oxygen evolution reaction (OER) in an alkaline medium while almost similar values of Tafel slope for HER and OER equivalent to 287.33 mV.dec−1 and 289.93 mV.dec−1 respectively in acidic medium. Thus, the compound 1 has excellent efficacy in catalyzing HER and OER in acidic as well as alkaline medium, which is ascribed to its distinctive 3D architecture. [ABSTRACT FROM AUTHOR]

In the realm of renewable energy technologies, the development of efficient and durable electrocatalysts is paramount, especially for applications like electrochemical water splitting. This research focuses on synthesizing a novel bimetallic metal‐organic framework (BMMOF11) using earth‐abundant elements, cobalt (Co) and cadmium (Cd). BMMOF11 showcases a distinctive structure with distorted octahedral chains of CoO and CdO, linked by benzene tricarboxylic acid (BTC). Our study primarily investigates the electrocatalytic efficiency of BMMOF11, particularly in water oxidation reactions. For practical analysis, BMMOF11 was anchored onto nickel foam, forming BMMOF11/NF, to evaluate its electrocatalytic properties. Electrochemical testing revealed that BMMOF11/NF begins water oxidation at an onset potential of 1.62 V versus RHE, demonstrating high activity with a lower overpotential of 0.4 V to achieve a current density of 10 mA/cm2. Moreover, BMMOF11/NF maintained stable water splitting performance, sustaining a current density of approximately 70 mA/cm2 under a voltage of 1.9 V relative to RHE. These findings indicate that BMMOF11/NF is a promising candidate for large‐scale electrochemical water splitting, offering a blend of high activity and stability. [ABSTRACT FROM AUTHOR]

Water oxidation of photosynthesis at the oxygen evolving complex (OEC) is driven by the polarization field induced by the photoelectric hole. By highlighting the role of the polarization field in reshaping the spin and orbit potentials, we reveal in this work the characteristics and underlying mechanism in the relatively simpler OEC evolutions within the states S 0 – S 2 prior to the water oxidation. The characteristic shifts of the density of states (DOS) of the electron donor Mn atom are observed in the vicinity of the Fermi surface to occur with the spin flips of Mn atoms and the change in the Mn oxidation states during the electron transfer. Notably, the spin flips of Mn atoms point to the resulting spin configuration of the next states. It is found that the electron transfer tends to stabilize the catalyst OEC itself, whereas the proton transfer pushes the evolution forward by preparing a new electron donor, demonstrating the proton-coupled electron transfer. Meanwhile, it shows that the Mn–O bonds around the candidate Mn atom of the electron donor undergo characteristic changes in the bond lengths during the electron transfer. These concomitant phenomena uncovered in first-principle calculations characterize the essential equilibrium of the OEC between the state evolution and stability that forms the groundwork of the dynamic OEC cycles. In particular, the characteristic undulation of the DOS around the Fermi level occurring at the proton-coupled electron transfer can be used to reveal crucial processes in a wide range of realistic systems. [ABSTRACT FROM AUTHOR]

Nickel coordination compounds featuring Ni–O bonds are key structural motifs in both bioinorganic and synthetic chemistries. They serve as precursors for organic substrate oxidation and are commonly invoked intermediates in water oxidation and oxygen reduction schemes. Herein, we disclose a series of well-defined dinuclear nickel complexes that, upon treatment with CO2 and H2O2, afford the first nickel-bound peroxycarbonate. This unprecedented nickel–oxygen intermediate is stabilized by hydrogen bonding templated across the bimetallic core. Contrasting copper and iron analogues, the nickel peroxycarbonate reversibly dissociates H2O2, a process that is shown to be accelerated by exogenous CO2. [ABSTRACT FROM AUTHOR]

Incorporating electrocatalytic active sites into the reticular framework allows for the design of novel catalytic structures promoting desired catalytic reactions with efficient mass transfer. However, to fully exploit the advantages of such a framework, it is crucial to ensure the electrochemical stability of the material. In this context, alkaline‐stable bimetallic MxNi2‐xCl2BTDD (M = Fe, Co) metal–organic frameworks (MOFs) are employed as electrocatalysts for alkaline water oxidation reaction (WOR) to understand the correlation between secondary metal incorporation and catalytic activity changes. For a specific Fe ratio within the MOF, the optimal catalytic activity is achieved at an overpotential of 315 mV at a WOR current density of 10 mA cm−2geo. Based on its well‐defined crystal structure and uniformly arranged metal nodes, which are not limited to specific facets, the cooperative electrocatalytic mechanism during the faradaic WOR process is investigated through operando Raman spectroscopy and density functional theory calculations. These results enable the interpretation of the electrochemical WOR mechanism based on MOF, providing a further fundamental understanding of electrocatalytic activity in bimetallic systems. [ABSTRACT FROM AUTHOR]

Discovering a competent charge transport layer promoting charge separation in photoelectrodes is a perpetual pursuit in photoelectrochemical (PEC) water splitting to achieve high solar‐to‐hydrogen (STH) conversion efficiency. Here, a conjugated polythiophene framework (CPF‐TTB) on Ta3N5 is elaborately electropolymerized, substantiating the hole transport behavior in their heterojunction. Tailored band structures of the CPF‐TTB/Ta3N5 reinforce the separation of photogenerated carriers, elevating a fill factor of the photoanode modified with a cocatalyst. The enhanced hole extraction enables the NiFeOx/CPF‐TTB/Ta3N5/TiN photoanode to generate a remarkable water oxidation photocurrent density of 9.12 mA cm−2 at 1.23 V versus the reversible hydrogen electrode. A tandem device combining the photoanode with a perovskite/Si solar cell implements an unbiased solar water splitting with a STH conversion efficiency of 6.26% under parallel illumination mode. This study provides novel strategies in interface engineering for metal nitride‐based photoelectrodes, suggesting a promise of the organic–inorganic hybrid photoelectrode for high‐efficiency PEC water splitting. [ABSTRACT FROM AUTHOR]

Electrocatalytic alcohol oxidation (EAO) is an attractive alternative to the sluggish oxygen evolution reaction in electrochemical hydrogen evolution cells. However, the development of high-performance bifunctional electrocatalysts is a major challenge. Herein, we developed a nitrogen-doped bimetallic oxide electrocatalyst (WO-N/NF) by a one-step hydrothermal method for the selective electrooxidation of benzyl alcohol to benzoic acid in alkaline electrolytes. The WO-N/NF electrode features block-shaped particles on a rough, inhomogeneous surface with cracks and lumpy nodules, increasing active sites and enhancing electrolyte diffusion. The electrode demonstrates exceptional activity, stability, and selectivity, achieving efficient benzoic acid production while reducing the electrolysis voltage. A low onset potential of 1.38 V (vs. RHE) is achieved to reach a current density of 100 mA cm−2 in 1.0 M KOH electrolyte with only 0.2 mmol of metal precursors, which is 396 mV lower than that of water oxidation. The analysis reveals a yield, conversion, and selectivity of 98.41%, 99.66%, and 99.74%, respectively, with a Faradaic efficiency of 98.77%. This work provides insight into the rational design of a highly active and selective catalyst for electrocatalytic alcohol oxidation. [ABSTRACT FROM AUTHOR]

Modulating of electronic structure of photocatalyst and integration of dual channel pathway are promising strategy for efficient photosynthesis of hydrogen peroxide (H2O2) from pure water without sacrificial agent and oxygen exposure. In this work, nontoxic aromatic dialdehyde is used to replace the commonly used toxic formaldehyde to form resorcinol‐phthalaldehyde resins through a hydrothermal method. The introducing of aromatic ring as π spacer increases the separation distance of electrons and holes to avoid their recombination. H2O2 can be produced via integrated oxygen reduction reaction (ORR) and water oxidation reaction (WOR) due to the suitable energy band positions and spatially separated reaction sites. Resorcinol‐p‐phthalaldehyde (RP) resin exhibits a promising H2O2 yield of 3351 µmol g−1 h−1 with high apparent quantum yield (AQY) of 14.9% at 420 nm and solar‐to‐chemical conversion (SCC) efficiency of 1.54%. This work provides a simple strategy to modulate the charge separation efficiency and redox reaction pathway on photocatalyst at molecular level design. [ABSTRACT FROM AUTHOR]

[Display omitted] To reveal the mechanism of charge transfer between interfaces of BiVO 4 -based heterogeneous materials in photoelectrochemical water splitting system, the cocatalyst was grown in situ using tannic acid (TA) as a ligand and Fe and Co ions as metal centers (TAFC), and then uniformly and ultra-thinly coated on BiVO 4 to form photoanodes. The results show that the BiVO 4 /TAFC achieves a superior photocurrent density (4.97 mA cm−2 at 1.23 V RHE). The charge separation and charge injection efficiencies were also significantly higher, 82.0 % and 78.9 %, respectively. From XPS, UPS, KPFM, and density functional theory calculations, Ligand-to-metal charge transfer (LMCT) acts as an electron transport highway in TAFC ultrathin layer to promote the concentration of electrons towards metal center, leading to an increase in the work function, which enhances the built-in electric field and further improves the charge transport. This study demonstrated that the LMCT pathway on TA-metal complexes enhances the built-in electric field in BiVO 4 / TAFC to promote charge transport and thus enhance water oxidation, providing a new understanding of the performance improvement mechanism for the surface-modified composite photoanodes. [ABSTRACT FROM AUTHOR]

[Display omitted] CeO 2 has been identified as a significant cocatalyst to enhance the electrocatalytic activity of transition metal phosphides (TMPs). However, the electrocatalytic mechanism by which CeO 2 enhances the catalytic activity of TMP remains unclear. In this study, we have successfully developed a unique CeO 2 -CoP-1–4 multishell microsphere heterostructure catalyst through a simple hydrothermal and calcination process. CeO 2 -CoP-1–4 exhibits great potential for electrocatalytic oxygen evolution reaction (OER), requiring only an overpotential of 254 mV to achieve a current density of 10 mA cm−2. Moreover, CeO 2 -CoP-1–4 demonstrates excellent operating durability lasting for 55 h. The presence of CeO 2 as a cocatalyst can regulate the microsphere structure of CoP, the resulting multishell microsphere structure can shorten the mass transfer distance, and improve the utilization rate of the active site. Furthermore, in situ Raman and ex situ characterizations, and DFT theoretical calculation results reveal that CeO 2 can effectively regulates the electronic structure of Co species, reduces the reaction free energy of rate-limiting step, thus increase the reaction kinetic. Overall, this study provides experimental and theoretical evidence to better comprehend the mechanism and structure evolution of CeO 2 in enhancing the OER performance of CoP, offering a unique design inspiration for the development of efficient hollow heterojunction electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] The anodic oxygen evolution reaction is a well-acknowledged side reaction in traditional aqueous electrochemiluminescence (ECL) systems due to the generation and surface aggregation of oxygen at the electrode, which detrimentally impacts the stability and efficiency of ECL emission. However, the effect of reactive oxygen species generated during water oxidation on ECL luminophores has been largely overlooked. Taking the typical luminol emitter as an example, herein, we employed NiIr single-atom alloy aerogels possessing efficient water oxidation activity as a prototype co-reaction accelerator to elucidate the relationship between ECL behavior and water oxidation reaction kinetics for the first time. By regulating the concentration of hydroxide ions in the electrolyte, the electrochemical oxidation processes of both luminol and water are finely tuned. When the concentration of hydroxide ions in electrolyte is low, the kinetics of water oxidation is attenuated, which limits the generation of oxygen, effectively mitigates the influence of oxygen accumulation on the ECL strength, and offers a novel perspective for harnessing side reactions in ECL systems. Finally, a sensitive and stable sensor for antioxidant detection was constructed and applied to the practical sample detection. [ABSTRACT FROM AUTHOR]

Crystal facet‐dependent photogenerated charge transfer at the semiconductor/current collector interface of photoelectrodes is equally important compared to that at the semiconductor/liquid interface for efficient photoelectrochemical (PEC) water splitting, which, however, is difficult to explore due to the rigid solid/solid interface in conventional photoelectrodes. Here, the facet‐dependent charge transfer at both semiconductor/liquid and semiconductor/collector interfaces in liquid metal‐embraced photoelectrodes is systematically investigated using faceted BiVO4 micro‐particles with different ratios of {110} and {010} facets as model materials. The results from the photo(electro)chemical and photophysical characterizations reveal that {010} facets outperform {110} facets at the semiconductor/liquid interface in triggering water oxidation due to the lower valence band maximum (VBM) of {010} facets, while {110} facets are more efficient at the semiconductor/metal interface for the collection of photogenerated electrons due to their higher conduction band minimum (CBM). Consequently, the photoelectrodes of liquid metal‐embraced BiVO4 particles exposing 53% {110} facets yield the best PEC performance for water splitting due to the well‐balanced photogenerated charge transfer at the interfaces of semiconductor/metal and semiconductor/liquid. [ABSTRACT FROM AUTHOR]

Conversion of CO2 into high‐value chemicals using solar energy is one of promising approaches to achieve carbon neutrality. However, the oxidation of water in the photocatalytic CO2 reduction is kinetically unfavorable due to multi‐electron and proton transfer processes, along with the difficulty in generating O−O bonds. To tackle these challenges, this study investigated the coupling reaction of photocatalytic CO2 reduction and selective propane oxidation using the Pd/P25 (1 wt%) catalyst. Our findings reveal a significant improvement in CO2 reduction, nearly fivefold higher, achieved by substituting water oxidation with selective propane oxidation. This substitution not only accelerates the process of CO2 reduction but also yields valuable propylene. The relative ease of propane oxidation, compared to water, appears to increase the density of photogenerated electrons, ultimately enhancing the efficiency of CO2 reduction. We further found that hydroxyl radicals and reduced intermediate (carboxylate species) played important roles in the photocatalytic reaction. These findings not only propose a potential approach for the efficient utilization of CO2 through the coupling of selective propane oxidation into propylene, but also provide insights into the mechanistic understanding of the coupling reaction. [ABSTRACT FROM AUTHOR]

Electrocatalysts for the oxygen evolution process must be both active and stable in order to make hydrogen from water using renewable power. Nitrogen‐doped carbon layer coated cobalt manganate particles were synthesized on carbon cloth using calcination method. The catalysts exhibited small particle sizes and graphitized carbon layer that covered the cobalt manganate, facilitating electron flow. Moreover, the nitrogen‐doped carbon layer enhanced the oxygen evolution reaction (OER) rate by reducing the potential required for surface reconstruction and optimizing electron distribution on the cobalt manganate surface. This electrocatalyst demonstrated a current density of 100 mA/cm2 at 1.56 V vs. RHE. Thus, this electrocatalyst shows promise as a novel OER catalyst for water oxidation in acidic aqueous solutions. [ABSTRACT FROM AUTHOR]

Artificial photosynthesis of H2O2 from H2O and O2 by visible light is a promising approach, but the efficiency is still unsatisfactory because of the inefficient O2 adsorption and proton supply. Here, terphenyl functionalized covalent triazine polymer (CTP‐TD) is prepared for efficient H2O2 production. Experimental and theoretical results show that terphenyl structure can promote O2 adsorption by regulating the oxygen evolution (O2→1O2) and improve proton supply by accelerating water oxidation. The terphenyl structure significantly promotes the singlet oxygen (1O2) production via the intersystem crossing (ISC) process. The electrophilic 1O2 is more easily adsorbed on the catalyst surface than O2. Simultaneously, the accumulated holes at the terphenyl structure lower water oxidation energy barriers and accelerate the water dehydrogenation process. This work provides a valuable reference and new inspiration for the polymer design of efficient H2O2 generation from the perspective of reactant supply. [ABSTRACT FROM AUTHOR]

Photosystem II (PSII) catalyzes the light-driven charge separation and water oxidation reactions of photosynthesis. Eukaryotic PSII core is usually associated with membrane-embedded light-harvesting antennae, which greatly increase the absorbance cross-section of the core. The peripheral antennae in different phototrophs vary considerably in protein composition and arrangement. Photosynthetic cryptophytes possess chlorophyll a/c binding proteins (CACs) that serve as their antennae. How these CACs assemble with the PSII core remains unclear. Here, we report the 2.57-Å resolution structure of cryptophyte PSII-CAC purified from cells at nitrogen-limited stationary growth phase. We show that each monomer of the PSII homodimer contains a core complex, six chlorophyll a/c binding proteins (CACs) and a previously unseen chlorophyll-binding protein (termed CAL-II). Six CACs are arranged as a double-layered arc-shaped non-parallel belt, and two such belts attach to the dimeric core from opposite sides. The CAL-II simultaneously interacts with a number of core subunits and five CACs. The distinct organization of CACs and the presence of CAL-II may play a critical role in stabilizing the dimeric PSII-CAC complex under stress conditions. Our study provides mechanistic insights into the assembly and function of the PSII-CAC complex as well as the possible adaptation of cryptophytes in response to environmental stresses. Structure of PSII-CAC from cryptophyte Rhodomonas salina reveals a distinct organization of CACs and the presence of CAL-II, which may play a critical role in stabilizing the dimeric PSII-CAC complex under stress conditions. [ABSTRACT FROM AUTHOR]

Rapid cost reduction of green hydrogen is essential for the large‐scale deployment of hydrogen‐based energy system. A major component in achieving this is the development of advanced water electrolyzers. Sluggish oxygen evolution reaction (OER) is the bottleneck for water electrolysis, and tremendous efforts have been devoted to develop electrocatalysts that accelerate the OER kinetics. Recent advances have highlighted the potential of precious metal‐free OER electrocatalyst capable of stable operation at current densities above 1 A cm2. This brings an opportunity of constructing new‐generation electrolyzer with lower cost and higher productivity. However, achieving such high operating current densities presents new challenges. This review summarize the recent progress of high‐performance OER catalysts, and identifies key factors that can be leveraged to enhance catalyst activity. These factors include interface/surface engineering, amorphous and crystal phase coupling, hierarchical structure design, structural reconstruction and phase conversion, high entropy catalyst, and defect engineering. Additionally, the pressing challenges that have been largely ignored in previous research is addressed, such as sustaining long‐term stability under crucial conditions, disadvantages of immobilized powder electrocatalysts, electrode scale design, the necessity of designing innovative electrolyzer cell designs and advance characterization techniques. [ABSTRACT FROM AUTHOR]

In this work, in situ-generated cobalt oxide was infused into g-BCN to fabricate a heterocomposite (CoBCN) with multiple active sites. The electronic structure of CoBCN was further modified via the introduction of n- (Ni) and p-(Fe) type metals to investigate the activities of CoBCN-type materials with loosely bound electrons for electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) which symbolize the reduction/oxidation of water and reduction of fuel gas oxygen that goes on in concurrent electrocatalytic and fuel cell. Experimental results indicated that not only the electronic nature of the surface but also the binding energy between the involved metals and intermediates varied accordingly for the association/dissociation steps, resulting in the superiority of p-doped materials in HER and the n-doped material in the OER and ORR. The HER activity was governed by Fe–CoBCN with an overpotential of 97 mV (@ 10 mA cm−2), whereas Ni–CoBCN showed superior performance for the OER and ORR with an overpotential and E 1/2 of 130 mV (@ 10 mA cm−2) and 0.79 V, respectively. p-/n-effect on CoBCN material for its multifunctional electrocatalytic activity for HER, OER and ORR. [Display omitted] • Fe and Ni oxide were doped individually to observe the p-/n-effect. • Fe–CoBCN dominated HER with a low overpotential due to facile Cat-H interaction. • Ni–CoBCN outperformed for OER and ORR with a low overpotential and E 1/2. [ABSTRACT FROM AUTHOR]

Regulating the intrinsic activity of electrocatalysts is an effective strategy towards outstanding behaviour for oxygen evolution reaction (OER). Herein, the rational design of a Mn–CoP@CoFe 2 O 4 core-shell heterojunction using nickel foam (NF) as a supporting material with special interface engineering has been investigated by a facile hydrothermal technique combined with phosphorization and electrodeposition method. The physical characterization demonstrates Mn–CoP@CoFe 2 O 4 core-shell heterostructure with Mn–CoP nanoneedles as core and CoFe 2 O 4 nanosheets as shell has been successfully acquired. The electrochemical measurements of the as-prepared Mn–CoP@CoFe 2 O 4 /NF core-shell heterojunction nanoarray electrode exhibit the superior electrocatalytic behaviour for OER (Tafel slope of 35.6 mV dec−1 and overpotential of 209.6 mV@10 mA cm−2). The remarkable OER behaviour may be ascribed to the sufficient active sites and the enhanced intrinsic activity due to the introduction of CoFe 2 O 4 and Mn element, which can regulate the electron structure and increase the turnover frequency. Furthermore, the Mn–CoP@CoFe 2 O 4 /NF electrode appears an excellent long-run stability during the OER process at 100 mA cm−2 for 100 h. Therefore, the construction of metal doping transition metal-based core-shell heterostructure electrocatalysts may be a promising way for the remarkable OER electrocatalytic performance towards water splitting. Mn–CoP@CoFe 2 O 4 core–shell heterostructure electrocatalyst revealed the remarkable OER behaviour and stability, ascribing to the sufficient active sites and the enhanced intrinsic activity by the introduction of CoFe 2 O 4 and Mn element, which can regulate the electron structure and increase the turnover frequency. [Display omitted] • Mn–CoP@CoFe 2 O 4 /NF core-shell heterostructure electrocatalyst was fabricated. • Mn–CoP@CoFe 2 O 4 /NF exhibited the outstanding OER behaviour in 1 M KOH. • Mn–CoP@CoFe 2 O 4 /NF electrode appeared an excellent long-run stability for OER in 100 mA cm−2 for 100 h. • Mn–CoP@CoFe 2 O 4 /NF electrode possessed sufficient active sites and enhanced intrinsic activity. [ABSTRACT FROM AUTHOR]

The increasing occurrence of saxitoxins in freshwaters is becoming a concern for water treatment facilities owing to its structural properties which make it resistant to oxidation at pH, 8. Hence, it is crucial to be able to monitor these toxins in surface and drinking water to protect public health. This review aims to outline the current state of knowledge related to the occurrence of saxitoxins in freshwaters and its removal strategies and provide a critical assessment of the detection methods to provide a basis for further development. Temperature and nutrient content are some of the factors that influence the production of saxitoxins in surface waters. A high dose of sodium hypochlorite with sufficient contact time or activated carbon has been shown to efficiently remove extracellular saxitoxins to meet the drinking water guidelines. While HILIC-MS has proven to be a powerful technology for more sensitive and reliable detection of saxitoxin and variants after solid phase extraction, ELISA is cost-effective and easy to use and is used by Ohio EPA for surveillance with a limit of detection of 0.015 μg/L. However, there is a need for the development of cost-effective and sensitive techniques that can quantify the variants of saxitoxin. [ABSTRACT FROM AUTHOR]

To explain the presence and spatial distribution of NO3− and N–NH3 in the Aquifer of the Metropolitan Area of Mexico City (AMAMC), a hydrogeochemical and isotopic analysis using 13CDIC (as well as the stable isotopes 18O and 2H) in groundwater was conducted. This aquifer is located in an old closed lacustrine volcano-sedimentary basin; some wells hosted in the semi-confined zone contain high N–NH3 concentrations, while others present NO3− contents in the recharge zones (hosted in an oxidizing environment). In this study, a change in the isotopic signature (primarily in 18O and 2H) was observed from the recharge zones to the basin center in some of the wells with high NO3− concentrations, this behavior can be attributed to evaporation during the incorporation of recently infiltrated water. In addition, the results for 13C (along with 2H) in wells with the highest N–NH3 concentrations exhibited an atypically broad range of values. Results indicated the occurrence of hydrogeochemical and/or biochemical processes in the aquifer (in an oxidizing or reducing environment), such as organic degradation, bacterial decomposition (primarily in the ancient Lake Texcoco and which acts as a natural sink for carbon, nitrogen, sulfur, and phosphorus), besides rock weathering and dissolution, which may be responsible for a very marked isotopic modification of the 13C (and, to a lesser extent, 2H). Methanotrophic bacterial activity and methanogenic activity may be related to N–NH3 removal processes by oxidation and residual water incorporation respectively, whereas the increase in the NO3− content in some wells is due to the recent contribution of poor-quality water due to contamination. [ABSTRACT FROM AUTHOR]

The oligomeric ruthenium‐based water oxidation catalyst, Ru(bda), is known to be experimentally anchored on graphitic surfaces through CH‐π stacking interactions between the auxiliary bda ([2,2′‐bipyridine]‐6,6′‐dicarboxylate) ligand bonded to ruthenium and the hexagonal rings of the surface. This anchoring provides control over their molecular coverage and enables efficient catalysis of water oxidation to dioxygen. The oligomeric nature of the molecule offers multiple anchoring sites at the surface, greatly enhancing the overall stability of the hybrid catalyst‐graphitic surface anode through dynamic bonding. However, the impact of this dynamic anchoring on the overall catalytic mechanism is still a topic of debate. In this study, a crucial proton‐coupled electron transfer event in the catalytic cycle is investigated using DFT‐based molecular dynamics simulations plus metadynamics. The CH‐π stacking anchoring plays a critical role not only in stabilizing this hybrid system but also in facilitating the proton‐coupled electron transfer event with possible vibronic couplings between the anchoring bonds motion and charge fluctuations at the catalyst – graphitic surface interface. Furthermore, this computational investigation displays the presence of a quartet spin state intermediate that can lead to the experimentally observed and thermodynamically more stable doublet spin state. [ABSTRACT FROM AUTHOR]

The development of the proton exchange membrane water electrolyzer (PEMWE) is still limited by the prohibitive cost and scarcity of iridium (Ir)‐based oxygen evolution reaction (OER) catalyst. This work presents a novel catalyst synthesized by precursor‐atomization and rapid joule‐heating method, successfully doping iridium atoms into polyvalent tungsten blends (W0, W5+, W6+) based on titanium substrate. The vacancy engineering of unsaturated tungsten oxide (W5+, W6+) reconstructs the electronic structure of the catalyst surface, which resulting in the low‐valence state iridium species, avoiding excessive oxidation of iridium and accelerating the catalytic kinetics. Meanwhile, metallic tungsten (W0) improves the conductivity of catalyst and guarantees the stable existence of oxygen vacancy. The TiIrWOx possesses excellent performance in acidic OER catalysis, requiring overpotential of only 181 mV to drive 10.0 mA cm−2, and exhibiting a high mass activity of 753 A gIr−1 at an overpotential of 300 mV. The membrane electrode assembly (MEA) with TiIrWOx as anode electrocatalyst can reduce the Ir consumption amount by >60% compared to commercial IrO2, and it can operated over 120 h at a current density of 1.0 A cm−2. [ABSTRACT FROM AUTHOR]

In this research, the heterogeneous catalysts of Fe3O4@SiO@TiO‐FePc and Fe3O4@SiO@TiO‐ CuPcN (FePc = iron (II) phthalocyanine and CuPcN = copper (II) tetraazaphthalocyanine), termed respectively as nanocomposites 1 and 2, were prepared by immobilizing the FePc and CuPcN complexes on the Fe3O4@SiO@TiO surface and used for the photocatalytic water oxidation reaction. Since phthalocyanine complexes have received very little attention as photocatalysts for water oxidation, the advantage of the synthesized photocatalyst owes to the ability of the phthalocyanine complex grafted on the titanium substrate to oxidize water in the photocatalytic reaction. The prepared nanocomposites were then studied by diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX), Fourier transform infrared (FT‐IR) spectroscopies, thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), Brunauer–Emmett–Teller (BET) analysis, ultraviolet diffuse reflectance (DRS), and photoluminescence (PL) spectroscopies. The photocatalytic response of water oxidation by nanocomposites 1 and 2 was investigated in the presence of silver nitrate as an electron recipient at ambient temperature. The progress of the water oxidation reaction was monitored with an oxygen meter. The amount of oxygen generated in the presence of nanocomposites 1 and 2 under visible light irradiation was found to be 2.6 and 2.1 mg L−1, respectively. Owing to the existence of magnetic material, these nanocomposites can be effortlessly removed from the response medium with an external magnet. The involved nanocomposites can be used up to three times in catalytic water oxidation reactions with no significant change in their photocatalytic activity. [ABSTRACT FROM AUTHOR]

The oxidation of multi-walled carbon nanotubes (MWCNTs) using cold plasma was investigated for their subsequent use as adsorbents for the removal of dyes from aqueous solutions. The properties of MWCNTs after plasma modification and their adsorption capacities were compared with pristine and chemically oxidized nanotubes. The modification process employed a reactor where plasma was generated through dielectric barrier discharges (DBD) powered by high-voltage nanosecond pulses. Various modification conditions were examined, such as processing time and pulse voltage amplitude. The degree of oxidation and the impact on the chemistry and structure of the nanotubes was investigated through various physicochemical and morphological characterization techniques (XPS, BET, TEM, etc.). Maximum oxidation (O/C = 0.09 from O/C = 0.02 for pristine MWCNTs) was achieved after 60 min of nanopulsed-DBD plasma treatment. Subsequently, the modified nanotubes were used as adsorbents for the removal of the dye methylene blue (MB) from water. The adsorption experiments examined the effects of contact time between the adsorbent and MB, as well as the initial dye concentration in water. The plasma-modified nanotubes exhibited high MB removal efficiency, with adsorption capacity proportional to the degree of oxidation. Notably, their adsorption capacity significantly increased compared to both pristine and chemically oxidized MWCNTs (~54% and ~9%, respectively). Finally, the kinetics and mechanism of the adsorption process were studied, with experimental data fitting well to the pseudo-second-order kinetic model and the Langmuir isotherm model. This study underscores the potential of plasma technology as a low-cost and environmentally friendly approach for material modification and water purification. [ABSTRACT FROM AUTHOR]

Among numerous semiconductors, BiVO4 has a suitable bandgap width, excellent valence band energy level and high activity for visible light water oxidation. It is an important oxygen evolution photocatalyst, but its carrier migration rate is still lower than other semiconductor materials. Therefore, in this paper, transition metal cations such as Fe3+ were selectively exchanged with V5+ in BiVO4 in a high-temperature Ar atmosphere by vapor phase cation exchange method, cationic bonds with strong binding force were formed at the interface between metal elements and catalysts, effectively accelerating bulk to surface charge separation. The adsorption energy and surface oxidation kinetics of the intermediate in the process of water oxidation were enhanced, and the photoelectrochemical properties of the intermediate were effectively improved. The vapor phase cation exchange between Fe3+ and V5+ of BiVO4 photoanode makes the metal element and the catalyst form a strong cationic bond at the interface, which greatly reduces the charge transport resistance to a certain extent, accelerates the water reaction kinetics, which can not only significantly improve the stability, but also increase the photocurrent density and significantly reduce the starting potential. [ABSTRACT FROM AUTHOR]

NiFe‐layered double hydroxide (NiFe‐LDH) stands out as a promising electrocatalyst for the oxygen evolution reaction (OER), but the structural transformations under OER conditions are not well understood. The structural evolution of highly crystalline NiFe‐LDH on nickel foam during OER testing in 1 M KOH solution was analyzed using IR, Raman, XRD, XPS techniques, and DFT calculations. Instability of interlayer species within the NiFe‐LDH, including protons, anions, and water molecules, was found to cause the crystal structure to undergo expansion or contraction during OER operation, decreasing crystallinity and roughening the LDH surface. This dynamic structural evolution is crucial for determining OER activity, and it was observed that surface structural changes of the LDH, along with Fe content, jointly determined the degree of change in its OER activity. Our findings provide insights into designing active water‐splitting electrocatalysts and highlight the relationship between OER activity and the structure of NiFe‐LDH. [ABSTRACT FROM AUTHOR]

The development of silicon (Si) photoanodes for photoelectrochemical (PEC) oxidation is highly crucial for the progress of solar‐driven hydrogen production. Apart from the typical water oxidation reaction or oxygen evolution reaction (OER), the urea oxidation reaction (UOR) is gaining more attention due to favorable thermodynamics. In this work, we study Si photoanodes modified with electrodeposited copper‐nickel (CuNi) alloy for OER and UOR. The optimized photoanodes exhibit a low onset potential of 1.15 V vs reversible hydrogen electrode (RHE) and a current density of 6 mA cm−2 at 1.23 V vs RHE (the thermodynamic potential for water oxidation) for OER. Further, CuNi alloy‐modified photoanodes can drive the UOR at a lower onset potential (1.05 V vs RHE) and generate a higher current density of 31 mA cm−2 at 1.23 V vs RHE. Importantly, the CuNi alloy can extend the stability for UOR under PEC conditions when compared to a planar Ni film deposited by a vacuum‐based process. This work demonstrates that CuNi alloy can further improve the properties of inhomogeneous metal‐insulator‐semiconductor Si photoanodes which can be efficiently utilized for both OER and UOR. [ABSTRACT FROM AUTHOR]