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Over the last decades, the transition metal dichalcogenide (TMD) materials have been intensively investigated for hydrogen evolution reaction (HER). Among many TMD catalysts, MoS2 and WS2 are the most efficient materials for HER application because of their advantages including earth abundance, facile synthesis, and high catalytic activities. Herein, a simple and scalable process is introduced which was employed to prepare the nanoflower (NF) heterostructure of MoS2 and WS2 (MoS2/WS2 NF). The superior catalytic activity of the synthesized MoS2/WS2 NF could be contributed by the unique properties of the heterostructure between WS2 and MoS2 materials. Low overpotential (251 mV) at a current density of 10 mA cm−2, small Tafel slope (61 mV dec−1), good conductivity, and superstability are the main properties of the prepared MoS2/WS2 NF. This work presents a new facile novel to prepare efficient catalysts which could be great candidates for HER and electrocatalytic application. [ABSTRACT FROM AUTHOR]

The catalytic performance of spinel oxide NiCo2O4 for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was investigated. It shows that NiCo2O4 synthesized via hydrothermal treatment at 90 ℃ followed by calcination at 350 ℃ exhibits excellent catalytic activity. Furthermore, Fe-doped MnO2 (marked as Fe-M) was introduced as a modifier to further improve the performance of NiCo2O4. As expected, the 20% Fe-M hybrid catalyst (NiCo2O4 modified with 20 wt% Fe-M) displays the best ORR and OER catalytic activity. This is evidenced by its high OER current density of 265 mA cm−2, high ORR current density of 220 mA cm−2, low OER Tafel slope of 119 mV dec−1, low ORR Tafel slope of 167 mV dec−1. These exceptional results can be attributed to the synergistic effect between NiCo2O4 and Fe-M. Based on synergistic effect, the 20% Fe-M hybrid catalyst exhibits the best catalytic activity for oxygen evolution reaction and oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

High-entropy materials (High-entropy Materials, HEMs) as a derivative of high-entropy alloys (High-Entropy Alloys, HEAs), have become potential oxygen evolution reaction (Oxygen Evolution Reaction, OER) catalytic materials in recent years. High entropy materials have many attractive properties due to their unique polyatomic structure. This study presents a novel synthesis strategy to successfully grow high-entropy sulfides in situ on the surface of high-entropy alloys by a combination of alkali etching and hydrothermal methods. The experimental results demonstrate that the prepared high-entropy sulfide electrode shows excellent catalytic performance for the OER in alkaline electrolytes. It has a lower overpotential compared to the original high-entropy alloy electrode. Additionally, it exhibits better reaction kinetics. In 1 M KOH electrolyte, only 362 mV of overpotential was required to achieve a current density of 20 mA·cm−2 with a Tafel slope of 120 mV·dec−1. The enhanced catalytic activity of the high-entropy sulfide electrode is due to the abundant presence of catalytic active sites. Additionally, the electrode benefits from reduced charge transfer impedance. The synergize of multiple metal elements also plays a significant role in its superior performance. This research demonstrates the potential value of high-entropy sulfide electrodes in the field of electrocatalytic oxygen evolution reaction. The high-entropy sulfide with excellent electrocatalytic OER activity and stability in alkaline media which prepared by hydrothermally sulfiding high-entropy alloy electrodes after alkali etching. The electrode requires only an overpotential of 362 mV to reach a current density of 20 mA cm−2, accompanied by a Tafel slope of 120 mV∙dec−1, and maintains its catalytic activity in 1 M KOH for at least 10 h. This work provides a new idea for the preparation of high-entropy materials mainly composed of non-precious metals, which can enhance the application potential of non-precious metal OER catalysts. [Display omitted] • A novel high-entropy sulfide electrocatalysts base on high-entropy alloy has been synthesized. • High-entropy catalyst with unique structures can be obtained by applying an alkali etching treatment. • High-entropy sulfide electrocatalysts exhibits a nano-needle-like morphology feature. • This work shows the potential of applying HEAs in the area of electrocatalytic oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

New heteroleptic dppe appended Co(III)-dithiocarbamate (dtc) complex cations with compositions [Co(S2CNEt2)2(dppe)](PF6) (Co-Et), [Co(S2CNPri2)2(dppe)](PF6) (Co-Pr) and [Co(S2CNBun2)2(dppe)](PF6) (Co-Bu) have been synthesized and characterized by microanalysis, spectroscopic methods and crystallographic analysis. The single crystal X-ray diffraction results indicated that in all three complexes, the coordination environment around Co(III) is distorted octahedral and Co(III) is coordinated to four sulfur centers of the two dtc ligands and the two phosphorus centers of the dppe ligand. These complexes serve as precursors to yield cobalt sulfide/cobalt phosphide nano-composites dCo-Et, dCo-Pr and dCo-Bu by solvothermal decomposition of Co-Et, Co-Pr and Co-Bu, respectively. The decomposed materials have been characterized by PXRD and SEM-EDAX and explored as potential electrocatalysts for both oxygen evolution and hydrogen evolution reactions in basic and acidic media, respectively. Catalytic activity is dependent on the precursor complex and best OER and HER activities are observed for dCo-Bu with an η10 of 230 mV and a Tafel slope of 192.11 mV dec−1 for the OER and an η10 of 470 mV and a Tafel slope of 126.21 mV dec−1 for the HER. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting offers a most promising pathway for "green hydrogen" generation. Even so, it remains a struggle to improve the electrocatalytic performance of non‐noble metal catalysts, especially bifunctional electrocatalysts. Herein, aiming to accelerate the hydrogen and oxygen evolution reactions, an oxygen‐bridged cobalt–chromium (Co‐O‐Cr) dual‐sites catalyst anchored on cobalt phosphide synthesized through MOF‐mediation are proposed. By utilizing the filling characteristics of 3d orbitals and modulated local electronic structure of the catalytic active site, the well‐designed catalyst requires only an external voltage of 1.53 V to deliver the current density of 20 mA cm−2 during the process of water splitting apart from the superb HER and OER activity with a low overpotential of 87 and 203 mV at a current density of 10 mA cm−2, respectively. Moreover, density functional theory (DFT) calculations are utilized to unravel mechanistic investigations, including the accelerated adsorption and dissociation process of H2O on the Co‐O‐Cr moiety surface, the down‐shifted d‐band center, a lowered energy barrier for the OER and so on. This work offers a design direction for optimizing catalytic activity toward energy conversion. [ABSTRACT FROM AUTHOR]

The commonly used "catalyst on carbon" architecture as a sulfur host is difficult to jointly achieve high gravimetric and volumetric energy densities for lithium–sulfur (Li–S) batteries due to the contradiction between low tap density/poor catalytic activity of carbon and the easy agglomeration of metal‐based compounds without carbon. Here, a non‐carbon‐dominated catalytic architecture using macroporous nickel/cobalt phosphide (NiCoP) is reported as the sulfur host for Li–S batteries. The macroporous framework, which accommodates a large amount of sulfur, can accelerate the electrochemical reaction kinetics by accelerated e− transport, Li+ diffusion, and superior adsorption and catalytic activity of inherent Ni2P/CoP heterostructures. The high tap density (0.45 g cm−3) and mechanically hard features contribute to the excellent structural and physicochemical stability of the NiCoP@S electrode after the pressing and rolling process. These features enable the Li–S coin cell to exhibit excellent electrochemical performance under conditions of high sulfur loading (10.2 mg cm−2) and lean electrolyte (electrolyte/sulfur of 2 µL mg−1). Inspiringly, the assembled pouch cell can simultaneously deliver a gravimetric energy density of 345.2 Wh kg−1 and an impressive volumetric energy density of 952.7 Wh L−1 based on the entire device configuration. [ABSTRACT FROM AUTHOR]

Transition metal phosphates have proved to be promising electrocatalysts for hydrogen evolution reactions (HER) of water splitting, however, further increasing their active sites and catalytic activity remains a major challenge. Herein, accordion-like Co-MOF with layered structure was synthesized. After subsequent carbonization and phosphidization, lamellar heterostructured Co/CoP nanocrystals encapsulated in a P, N co-doped C matrix (Co/CoP@PNC) was obtained. Heterojunction provides abundant active sites and improves electron transfer rate. Additionally, the effect of phosphating degree on the electrocatalytic activity was studied. In the alkaline electrolyte, the current density of the optimized Co/CoP@PNC-10 for HER reached 10 mA cm−2 at overpotential of 137 mV in 1.0 M KOH, which was superior to most of transition metal-based electrocatalysts. This work provides new guidance for the design and development of transition metal-based electrocatalysts. Co/CoP heterojunction embedded in P, N co-doped C matrix (Co/CoP@PNC) was prepared through further carbonization and phosphidization, the optimized Co/CoP@PNC exhibited excellent catalytic activity for alkaline HER. [Display omitted] • With accordion-like Co-MOF as the precursor, Co/CoP heterojunction embedded in P, N co-doped C matrix (Co/CoP@PNC) was prepared through further carbonization and phosphidization. • The phase and catalytic activity of the sample are related to the phosphating degree. • The optimized Co/CoP@PNC-10 exhibited the best performance among the series, with an overpotential of 137 mV at a current density of 10 mA cm−2 for alkaline HER. • P, N co-doped C substrate and Co/CoP heterojunction promote the overall HER performance through synergistic effect. [ABSTRACT FROM AUTHOR]

In this paper, a novel Pt/CoP/C photo-electro synergistic catalyst was successfully synthesized by a hydrothermal method combined with phosphorus doping treatment. The addition of Vulcan XC-72R is in favor of effectively preventing agglomeration of active catalytic sites, resulting in more uniform and smaller Pt and CoP nanoparticles. The as-obtained Pt/CoP/C shows excellent photo-electro catalytic performance for the HER with simulated solar light irradiation. The optimal hydrogen production is 5384.18 mmol h−1 g−1, which is obviously higher than that of the commercial catalyst (20 wt% Pt/C: 4608.52 mmol h−1 g−1). The research results show that introducing cobalt phosphide into the Pt catalyst can improve the electrocatalytic activity and stability for the HER; in particular, the existence of Co3O4 in Pt/CoP/C leads to an efficient photo-electro catalysis under irradiation, which significantly improves the catalytic activity of Pt. The results above provide a novel strategy for the rational design of cost-effective Pt-based composites towards a fast HER. [ABSTRACT FROM AUTHOR]

Seawater electrolysis is a viable method for producing hydrogen on a large scale and low-cost. However, the catalyst activity during the seawater splitting process will dramatically degrade as salt concentrations increasing. Herein, CoP is discovered that could reject chloride ions far from catalyst in electrolyte based on molecular dynamic simulation. Thus, a binder-free electrode is designed and constructed by in-situ growth of homogeneous CoP on rGO nanosheets wrapped around the surface of Ti fiber felt for seawater splitting. As expected, the as-obtained CoP/rGO@Ti electrode exhibits good catalytic activity and stability in alkaline electrolyte. Especially, benefitting from the highly effective repulsive Cl− intrinsic characteristic of CoP, the catalyst maintains good catalytic performance with saturated salt concentration, and the overpotential increasing is less than 28 mV at 10 mA cm−2 from 0 M to saturated NaCl in electrolyte. Furthermore, the catalyst for seawater splitting performs superior corrosion-resistance with a low solubility of 0.04%. This work sheds fresh light into the development of efficient HER catalysts for salinity tolerance hydrogen evolution. Seawater electrolysis for hydrogen production is limited by the poor salinity tolerance of catalysts. CoP was found to repel chlorine while attracting H2O molecules to form a thin layer on the catalyst surface, thus constructing a corrosion-resistant CoP/rGO@Ti catalyst for seawater splitting. [ABSTRACT FROM AUTHOR]

Cobalt phosphide (CoP) is a promising electrocatalyst due to its abundance and excellent stability in alkaline solution. However, its poor conductivity and intrinsic catalytic activity limit its potential in electrochemical water splitting. To address this, a heterogeneous atom doping strategy has been proposed to synthesize magnesium-doped cobalt phosphide nanoneedle arrays, or Mg-doped CoP. Our theoretical calculations show that transition metal Mg atoms doping into the CoP lattice can enhance the electronic structure and modulate the free energy of reacting species, resulting in a significant improvement in the intrinsic catalytic activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) process. The electrochemical tests reveal that the optimal 10% Mg-doped CoP nanoneedle arrays exhibit outstanding HER and OER electrocatalytic activities with overpotential values of 85 and 236 mV at 10 mA/cm2, respectively, outperforming previously reported CoP-based catalysts. This study not only presents a strategy to enhance the catalytic activity of CoP-based materials, but also offers a reference for achieving efficient electrochemical hydrogen production by hydrolysis. [Display omitted] • The charge compensation effect optimizes not only the electronic structure but also the free energy of H∗ and HOO∗ species. • The low-valent Mg2+ ions replace part of the Co3+ sites in the CoP lattice. • The creation of phosphorus vacancies in adjacent sites to maintain electroneutrality. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) plays a vital role for the production of pure hydrogen with zero carbon release. Developing high efficiency non-noble metal electrocatalysts could reduce its cost. Here, vanadium doped cobalt phosphide grown on carbon cloth (CC) was synthesized by the low temperature electrodeposition–phosphorization method. The influence of V dopants on the structural, morphological, and electrocatalytic performance of Vx–Co1−x–P composites was also investigated in-depth. Impressively, the optimized amorphous V0.1–Co0.9–P nano-electrocatalyst exhibits outstanding catalytic activity with a low overpotential of 50 mV at a current density of 10 mA cm−2 and a small Tafel value of 48.5 mV dec−1 in alkaline media. The results showed that V dopants in the composite change its crystal structure from the crystalline phase to the amorphous phase, resulting in the introduction of V–O sites, which regulate the electron density of the active sites and the exposure of surface active sites and thus promote the electrocatalytic HER process. This work provides a novel idea for the fabrication of high-efficiency metal phosphide based electrocatalysts. [ABSTRACT FROM AUTHOR]

In this paper, using density functional theory (DFT) methods, we meticulously investigated the structural properties of cobalt phosphide (CoP) and its Cu‐ and Ni‐doped counterpart. Then, on the surfaces of three catalysts, the hydrogen evolution reaction mechanism of ammonia borane (NH3BH3) was examined in turn, and four possible hydrogen evolution reaction paths of NH3BH3 on the catalyst surface were reviewed. The optimal reaction channel for each catalyst was found by comparing the activation energies of the control steps for several reaction paths, and activation energies of the optimal reaction for CoP, Cu, and Ni‐doped CoP were 31.4, 30.4, and 30.8 kcal/mol, respectively. Cu‐ and Ni‐ doped were beneficial to improve the hydrogen evolution reaction activity of NH3BH3. At the same time, the band structures and density of states of the stable catalysts were calculated. The results showed that near the fermi level, the electron cloud density of Cu and Ni‐doped CoP catalysts increased. The energy gap values of the three catalysts are 43.8, 41.0, and 41.7 kcal/mol, respectively, and the energy gap values of Cu and Ni doped CoP catalysts decrease. The energy gap values of the three catalysts are inversely proportional to their catalytic activities. We believe that these two factors together contribute to the increased catalytic activity of the doped CoP. Our results revealed the correlation between the physical properties of CoP and its metal‐doped catalysts and their catalytic activity. [ABSTRACT FROM AUTHOR]

In this paper, using density functional theory (DFT) methods, we meticulously investigated the structural properties of cobalt phosphide (CoP) and its Cu‐ and Ni‐doped counterpart. Then, on the surfaces of three catalysts, the hydrogen evolution reaction mechanism of ammonia borane (NH3BH3) was examined in turn, and four possible hydrogen evolution reaction paths of NH3BH3 on the catalyst surface were reviewed. The optimal reaction channel for each catalyst was found by comparing the activation energies of the control steps for several reaction paths, and activation energies of the optimal reaction for CoP, Cu, and Ni‐doped CoP were 31.4, 30.4, and 30.8 kcal/mol, respectively. Cu‐ and Ni‐ doped were beneficial to improve the hydrogen evolution reaction activity of NH3BH3. At the same time, the band structures and density of states of the stable catalysts were calculated. The results showed that near the fermi level, the electron cloud density of Cu and Ni‐doped CoP catalysts increased. The energy gap values of the three catalysts are 43.8, 41.0, and 41.7 kcal/mol, respectively, and the energy gap values of Cu and Ni doped CoP catalysts decrease. The energy gap values of the three catalysts are inversely proportional to their catalytic activities. We believe that these two factors together contribute to the increased catalytic activity of the doped CoP. Our results revealed the correlation between the physical properties of CoP and its metal‐doped catalysts and their catalytic activity. [ABSTRACT FROM AUTHOR]

The development of efficient, durable and economical catalysts based on non-precious metals for the controllable and fast hydrogen evolution from chemical hydrogen storage materials is highly desirable for the hydrogen economy. Herein, we introduce an advanced catalytic system by in situ encapsulating cobalt phosphide (CoP) nanoparticles into a quasi-metal–organic framework (quasi-Co-MOF-74) through a smart pyrolysis method. The designed synergic structure of CoP@quasi-Co-MOF-74 facilitates the efficient adsorption and activation of reactants, and achieves superior catalytic activity for the dehydrogenation of ammonia borane (AB). The extremely high hydrogen generation rate (HGR) of 9790 mL min−1 gcat−1 achieved by this catalytic system is 13.1, 4.4, and 46.5 times higher than that of quasi-Co-MOF-74, CoP, and CoP@C counterparts, respectively. Furthermore, CoP@quasi-Co-MOF-74 also delivers a high turnover frequency (TOF) of 55.9 min−1 and a low activation energy of 38.22 kJ mol−1 for the catalytic hydrolysis of AB, which compares favorably to most of the previously reported transition metal phosphide and cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

The enhancement in intrinsic catalytic activity and material conductivity of an electrocatalyst can leads to promoting HER activity. Herein, a successful nitrogenation of CoS 2 (N–CoS 2) catalyst has been investigated through the facile hydrothermal process followed by N 2 annealing treatment. An optimized N–CoS 2 catalyst reveals an outstanding hydrogen evolution reaction (HER) performance in alkaline as well as acidic electrolyte media, exhibiting an infinitesimal overpotential of −0.137 and −0.097 V at a current density of −10 mA/cm2 (−0.309 and −0.275 V at −300 mA/cm2), corresponding respectively, with a modest Tafel slope of 117 and 101 mV/dec. Moreover, a static voltage response was observed at low and high current rates (−10 to −100 mA/cm2) along with an excellent endurance up to 50 h even at −100 mA/cm2. The excellent catalytic HER performance is ascribed to improved electronic conductivity and enhanced electrochemically active sites, which is aroused from the synergy and mutual interaction between heteroatoms that might have varied the surface chemistry of an active catalyst. • N–CoS 2 catalyst was fabricated on the microporous Ni foam architecture via a hydrothermal procedure pursued by N 2 treatment. • Small overpotentials in alkaline (−0.137 V) and acidic (−0.97 mV) electrolyte media and associated low Tafel slope. • Excellent long–term sustainability at low and high current rate in alkaline and acidic electrolyte media. • The incorporation of heteroatoms leads to the varied electrocatalytically active sites and improved conductivity. [ABSTRACT FROM AUTHOR]

[Display omitted] A new palladium(0) nanocatalyst is developed to enhance the catalytic efficiency of precious metal catalysts in hydrogen generation from the hydrolytic dehydrogenation of ammonia borane. Magnetically separable Pd0/Co 3 O 4 nanocatalyst can readily be obtained by the reduction of palladium(II) cations impregnated on cobalt(II, III) oxide at room temperature. The obtained Pd0/Co 3 O 4 nanocatalyst with 0.25% wt. palladium loading has outstanding catalytic activity with a record turnover frequency of 3048 min−1 in the releasing H 2 from the hydrolysis of ammonia borane at 25.0 °C. They also provide outstanding reusability even after the tenth run of the hydrolysis of ammonia borane at 25.0 °C. The high activity and superb stability of magnetically isolable Pd0/Co 3 O 4 nanoparticles are attributed to the favorable interaction of palladium with the surface of reducible cobalt oxide. [ABSTRACT FROM AUTHOR]

[Display omitted] As a kind of high-performance and cost-efficient electrocatalyst in water splitting, the transition bimetal phosphides exhibit a promising prospect. Here, the composite of cobalt molybdenum phosphide nanoparticles embedded in crosslinked nitrogen-doped carbon nanofiber (Co 0.4 Mo 0.6 P@CL-NCNF) has been synthesized via an electrospinning process and pyrolysis treatment. As an effective hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalyst, the Co 0.4 Mo 0.6 P@CL-NCNF only requires the overpotentials of 81 mV and 219 mV at the current densities of 10 mA cm−2 and 20 mA cm−2, respectively. Moreover, the water electrolyzer with the Co 0.4 Mo 0.6 P@CL-NCNF as the cathode and anode catalysts requires a cell voltage of 1.59 V to reach a current density of 10 mA cm−2. The Co 0.4 Mo 0.6 P@CL-NCNF also achieves the excellent stability up to 24 h for HER, OER and overall water spitting in 1.0 M KOH. The excellent catalytic activity of the Co 0.4 Mo 0.6 P@CL-NCNF is benefits from the synergistic effect between components and the crosslinked structure of carbon nanofiber. Thus, the research provides a promising method for preparing carbon-based TMPs materials towards electrocatalysis. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

• NPC layer-confined CoP-anchored NNM catalyst (NNMCoP@ NPC/NF) on nickel foam. • Synergies of CoP and NNM regulate the electronic structure to enhance HER/OER activity. • The NPC-confined layer maintains catalytic activity and stability in cooperation with CoP. • Electrocatalyst exhibits remarkable performance for water-splitting with long stability time (>100 h). Aiming at the problems of low catalytic activity and poor stability of nickel molybdate-based catalysts. Herein, we successfully prepared nitrogen and phosphorus co-doped carbon (NPC) layer-confined cobalt phosphide (CoP)-anchored nano-cuboid nickel molybdate (NNM) catalysts (NNM-CoP@NPC/NF) on nickel foam (NF) by hydrothermal and phosphating methods. The strong interaction between CoP and NNM is verified by experimental characterization and theoretical calculation, which improves the electronic structure of NNM and reduces the orbital energy of the central anti-bond, thus optimizing the adsorption and desorption of reaction intermediates/products. NiOOH and MoO 4 2− formed by reforming the catalyst under the action of NPC-confined layer maintain catalytic activity and stability in cooperation with CoP and NPC, respectively. Accordingly, in the assembled two-electrode system NNM-CoP@NPC/NF, the cell voltage of only 1.51 V is needed to drive a current density of 10 mA cm−2. More importantly, the current density remained at 100 mA cm−2 for 100 h under the voltage of 1.66 V with almost no attenuation. This strategy of constructing interface regulation and confinement provides a new insight for improving the activity and stability of water splitting in alkaline media. [ABSTRACT FROM AUTHOR]

Given the great importance of cobalt catalysts supported by benchmark bis(imino)pyridine in the (oligo)polymerization, a series of dibenzopyran-incorporated symmetrical 2,6-bis(imino) pyridyl cobalt complexes (Co1–Co5) are designed and prepared using a one-pot template approach. The structures of the resulting complexes are well characterized by a number of techniques. After activation with either methylaluminoxane (MAO) or modified MAO (MMAO), the complexes Co1–Co4 are highly active for ethylene polymerization with a maximum activity of up to 7.36 × 106 g (PE) mol−1 (Co) h−1 and produced highly linear polyethylene with narrow molecular weight distributions, while Co5 is completely inactive under the standard conditions. Particularly, complex Co3 affords polyethylene with high molecular weights of 85.02 and 79.85 kg mol−1 in the presence of MAO and MMAO, respectively. The 1H and 13C NMR spectroscopy revealed the existence of vinyl end groups in the resulting polyethylene, highlighting the predominant involvement of the β-H elimination reaction in the chain-termination process. To investigate the mechanism underlying the variation of catalytic activities as a function of substituents, multiple linear regression (MLR) analysis was performed, showing the key role of open cone angle (θ) and effective net charge (Q) on catalytic activity. [ABSTRACT FROM AUTHOR]

A hierarchically ordered porous carbon electrocatalyst with exclusively surface‐anchored cobalt species, dubbed Co@HOPC, is synthesized from polyaniline and cobalt‐functionalized silica microparticles templates, and its high electrocatalytic activity for the oxygen evolution reaction (OER) is demonstrated. The material requires a small potential (320 mV) to drive the reaction with a current density of 10 mA cm−2 and a small Tafel slope of 31.2 mV dec−1. Moreover, Co@HOPC shows better catalytic activity for OER than in situ cobalt‐doped and surface cobalt‐loaded hierarchically ordered porous carbon materials synthesized by traditional methods. This is due to the abundant surface cobalt species present in Co@HOPC and the material's good electrical conductivity. This work provides a new strategy to utilize functionalized silica microparticles as templates to synthesize hierarchically ordered porous carbon materials with metal‐rich surfaces and efficient electrocatalytic activities. [ABSTRACT FROM AUTHOR]

Summary: For green‐hydrogen production through a promising electrolytic water splitting, cobalt phosphide is in the spotlight as one of the new affordable materials to replace currently used noble‐metal catalysts. In this study, we fabricate hollow cobalt phosphide (CoP) nanofibers with advanced nanostructure using electrospinning and phosphidation. Due to their unique architecture and oxygen‐rich surface characteristics, the novel hollow‐structure CoP nanofibers effectively increase hydrogen evolution reaction catalytic activity with the low overpotentials of 91 mV (for acid) and 63 mV (for alkaline). Using in situ Raman spectroscopy, it is confirmed that high‐oxygen‐containing CoP catalysts could transform the CoOOH phase under alkaline conditions, which offer faster water dissociation kinetics. Furthermore, CoP nanofibers exhibited excellent durability even after 30000th accelerated degradation test cycles and overall water splitting for 40 h. [ABSTRACT FROM AUTHOR]

• 1. The RVCPM has excellent HER and OER catalytic activity. • 2. Doping affects the filling of the catalyst's orbital electrons. • 3. Heterogeneous interfaces lead to optimized local charge distribution. Bifunctional electrocatalysts that exhibit excellent catalytic activity for both hydrogen (HER) and oxygen evolution reactions (OER) are ideal for alkaline overall water splitting. The unique structure and diverse composition of cobalt phosphide catalysts are highly favorable for enhancing catalytic reaction kinetics. However, cobalt phosphide electrocatalysts typically exhibit insufficient OER activity. To overcome this text, we synthesized a Ru and V co-doped CoP-coupled highly conductive MXene catalyst with nano-arrays by in-situ growth on the surface of carbon cloth. The HER and OER overpotentials of the catalyst at 10 mA cm−2 current density were 30 and 206 mV, respectively. Furthermore, a series of physicochemical characterizations and first-principles calculations demonstrated that the increased HER and OER activities resulted from the synergistic effect established by the double doping and heterostructure. This effect produced an effective modulation of the d-band center of the catalysts, promoting adsorption effects on the intermediates. In conclusion, this work presents a novel approach to improving the electrocatalytic activity of phosphides and provides a faster and more environmentally friendly method for separating hydrogen from water. [ABSTRACT FROM AUTHOR]

• Ultrasmall molybdenum carbide α − MoC 1 − x nanoparticles (1.6 nm) and a hybrid material composed of α − MoC 1 − x and reduced graphene oxide (rGO/ α − MoC 1 − x ) were synthesized by a one-pot oleylamine-mediated at a low temperature. • The materials were evaluated as electrocatalysts for the hydrogen evolution reaction (HER) in the acid medium, evidencing quite large activity for the HER. • The synthesis route is simple with low cost and energy consumption, showing a high potential to develop efficient and inexpensive catalysts for HER. Ultrasmall molybdenum carbide α − MoC 1 − x nanoparticles (1.6 nm) and the hybrid material rGO/ α − MoC 1 − x supported in reduced graphene oxide (rGO) were synthesized by a one-pot oleylamine-mediated route at low-temperature (613 K). They were evaluated as electrocatalysts for the hydrogen evolution reaction (HER) in the acid medium after surface cleaning with an ethanol-acetic acid solution. The electrocatalysts were also thermal treated (N 2 flow, 773 K/30 min) and compared with untreated ones. Quite large HER activity was observed for the α − MoC 1 − x compared with the rGO/ α − MoC 1 − x and rGO/ α − MoC 1 − x − 773. In addition, after cycling, all catalysts showed considerable performance improvement assigned to removing residual oleylamine molecules from the electrocatalyst's surface. Compared to the unsupported sample, the lower catalytic activity in the supported materials was attributed to the ultrasmall carbide nanoparticles oxidation increases. The route is simple, with low costs and energy consumption, showing a high potential to develop efficient electrocatalysts for HER. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogen is considered as a viable alternative to traditional fossil fuels. Hydrogen evolution reaction (HER) by electrochemical water splitting is the most reliable and effective way for the sustainable production of pure hydrogen. The design and synthesis of highly active and stable non-noble-metal-based electrocatalysts is the core of the large-scale application of this technology. Herein, peony petal-like CoMnP/NF nanomaterials growing on nickel foam (NF) are prepared via facile hydrothermal and phosphorization methods. The results showed that CoMnP/NF had excellent HER activity in acidic and alkaline media. In 0.5 M H 2 SO 4 , CoMnP/NF only needed 66.6 mV overpotential to drive the current density of 10 mA cm−2, with a Tafel slope of 38.8 mV dec−1. In addition, a particularly low overpotential of 53.9 mV and Tafel slope of 63 mV dec−1 are required to achieve the same current density in the 1 M KOH electrolyte. Meanwhile, the electrocatalyst showed good stability after 1000 cyclic voltammetry tests and 12 h I-T tests. In the 1 M KOH electrolyte, the current density of 10 mA cm−2 achieved with only 1.70 V battery voltage, and the electrocatalyst showed excellent stability. The performance of CoMnP/NF can be attributed to the synergistic effect between Co and Mn atoms and the high electrochemical surface area (ECSA). This study provides a valuable strategy for the synthesis of non-precious metals and high-performance catalytic materials. • Peony petal-like CoMnP/NF is prepared via facile two-step methods. • CoMnP/NF electrocatalyst exhibit excellent catalytic activity and high stability. • Mn doping could improve catalytic activity. [ABSTRACT FROM AUTHOR]

Achieving an efficient electrochemical hydrogen evolution reaction (HER) implies continuous development of new electrocatalysts for reducing the electrolytic energy consumption with the improvement of the stability and economical preparation in commercial applications. In this article, a binary transition-metal (Co/Ni) phosphide incorporated with an N-doped porous carbon (NPC) carrier was synthesized via a homogeneous polymerization followed by a high-temperature carbonizing and phosphating process, which was characterized by various techniques such as XRD, XPS, SEM, and EDS. The binary metal-based phosphide material (CoxPy/NixPy-NPC) exhibits high efficient catalytic activity for HER with low overpotential of 126 mV and 203 mV at 10 mA mg−1 in 1.0 M KOH and seawater with KOH added, respectively. Also, it exhibits satisfactory stability for a 10 h continuous test in the alkaline electrolyte. Furthermore, CoxPy/NixPy-NPC has good HER performance in natural seawater electrolyte with a potential difference of 110 mV (based on Pt/C at 10 mA mg−1), which is superior or close to that of other metal phosphides reported in literature. The excellent catalytic performance can be attributed to the synergistic effects of CoxPy and NixPy nanoparticles, protecting the effect of NPC to CoxPy and NixPy from aggregation. This work may provide an economic and convenient method to produce carbon-supported bimetallic phosphides as electrocatalytic materials. [ABSTRACT FROM AUTHOR]

Here, a new strategy that combines accessible active sites and multiphase synergy in a simple process is developed for constructing bifunctional electrocatalysts toward overall water splitting. By using metal–organic framework (MOF) nanosheets hydrothermally grown on pre-oxidized nickel foam (denoted by Co2(OH)2(BDC)/NiO/NF) as a precursor, two novel heterogeneous nanosheet arrays including a cobalt phosphide nanoparticle embedded carbon nanotube nanosheet array supported by phosphorized nickel foam (denoted by CoP-CNT/Ni2P/NF) and a cobalt phosphide nanorod decorated carbon nanosheet array supported by oxidized nickel foam (denoted by CoP-C/NiO/NF) are prepared. Both were confirmed to be highly efficient for hydrogen and oxygen evolution reactions. In particular, CoP-C/NiO/NF exhibits higher catalytic activity toward the hydrogen evolution reaction (η100 = −131 mV), promoted by the synergy of oxidized nickel foam. CoP-CNT/Ni2P/NF performs better in the oxygen evolution reaction (η50 = 301 mV), benefiting mainly from its improved electrochemically active surface area. The two catalysts match well in overall water splitting with satisfactory activity (η10 = 1.57 V) and stability when directly applied in a two-electrode cell. This method will bring new inspiration to maximize the electrocatalytic efficiency of MOF-derived catalysts for energy conversion applications in the future. [ABSTRACT FROM AUTHOR]

The exploration of highly active bifunctional electrocatalysts for acidic electrochemical water splitting has attracted wide attention due to their importance in polymer electrolyte membrane (PEM) electrolyzers. However, existing catalysts normally suffer from low catalytic efficiency under acidic conditions. Herein, we developed a series of Ir-doped CoP nanowires arrays on carbon cloth (Ir-CoP/CC) materials, realizing prominently improved bifunctional catalytic activity for overall water splitting in an acidic medium. The optimized Ir4-CoP/CC catalyst exhibits the smallest overpotential of 38 mV and 237 mV to reach 10 mA cm−2 for HER and OER, respectively. Through systematic experimental research, we find the best intrinsic activity belongs to Ir3-CoP/CC catalyst, which presents superior bifunctional performance with the most economical usage of Ir. As a result, the best acidic water splitting electrolyzer displays a very low voltage of 1.50 V at 10 mA cm−2. This work provides a novel strategy to develop highly active bifunctional catalysts for acidic electrochemical water splitting. [ABSTRACT FROM AUTHOR]

The development of highly efficient, stable, eco-friendly and low-cost noble-metal-free electrocatalysts is still a great challenge to generate large scale hydrogen fuel from water. In this concern, self-supported WP 2 and WP nanosheet (NS) arrays were prepared through an in-situ solid-phase phosphidation of WO 3 nanosheet arrays on carbon cloth (CC), whereas, different phosphating temperatures of 650 °C, 800 °C for 2 h, has been utilized to attain different WP 2 NS/CC, WP NS/CC catalysts. Remarkably, the electrocatalysts of WP 2 and WP NS arrays exhibit an outstanding hydrogen evolution (HER) performance in acidic environment, with a low overpotential of 140 mV and 175 mV at 10 mA cm−2, a Tafel slope of 85 mV dec−1 and 103 mV dec−1, respectively. Furthermore, Density Functional Theory (DFT) calculations reveal that the enhanced HER activity of WP 2 catalyst is attributed to the lowered hydrogen adsorption free energy on WP 2 surface, which is much lesser than that on the WP catalyst surface. As a result, WP 2 exhibit superior intrinsic catalytic activity than WP. This study offers a valuable way for the synthesis of highly efficient three-dimensional self-supporting catalytic electrodes, and beneficial for realizing the intrinsic electrocatalytic properties of tungsten phosphide for improved water splitting reactions. Self-supported WP 2 and WP nanosheet arrays were successfully synthesis at different phosphating temperatures for efficient electrocatalytic hydrogen evolution. Image 1 • Self-supported WP 2 and WP nanosheet arrays were synthesized. • Adjust phosphating temperatures obtained different WP 2 , WP catalysts. • WP 2 and WP NS arrays exhibit an outstanding hydrogen evolution performance. • DFT calculations reveal WP 2 exhibit better intrinsic catalytic activity than WP. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate morphology‐controlled synthesis of flower‐like cobalt phosphide decorated on nitrogen doped reduced graphene oxide (NrGO), which act as bifunctional electrocatalysts toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The as‐synthesized CoP‐NrGO, formed via hydrothermal reaction followed by gas‐solid reaction, attains an OER current density of 10 mA cm−2 at an overpotential of 0.38 V, which is on par with that of its Co(OH)2‐NrGO counterpart and the benchmarked IrO2 catalyst. On the other hand, the conversion of Co(OH)2 to CoP is seen to improve its HER performance drastically. CoP‐NrGO reached a current density of 10 mA cm−2 at an overpotential of 0.184 V which is 0.204 V anodic to Co(OH)2‐NrGO. The improved performance could be attributed to reduced charge transfer resistance following the phosphidation process. From the comparison of the electrocatalytic performance of the catalysts, it can be inferred that phosphidation has a considerable effect only on the cathodic HER. [ABSTRACT FROM AUTHOR]

Designing core‐shell heterostructures is essential for electrocatalytic hydrogen evolution reaction (HER). In this study, ultrathin MoS2 sheets are uniformly anchored on CoxP/nitrogen dual‐doped carbon nanocubes (CoxP/NC) through a template sacrificial method followed by a hydrothermal reaction. The resultant hybrid CoxP/NC@MoS2 possesses a core‐shell structure and superior catalytic activity to individual counterparts. The hybrid catalyst needs a low overpotential of 148 mV to drive the current density of 10 mA cm−2, together with an extremely small Tafel slope of 33 mV dec−1 and outstanding stability in acidic media. Most importantly, the best catalytic activity is achieved by coupling MoS2 nanosheets with the matrix CoxP/NC rather than Co/NC. The remarkably high HER activity of CoxP/NC@MoS2 mainly benefits from the core‐shell feature and strong synergistic interaction between CoxP/NC and MoS2. The present study inspires a continuous exploration of engineering MoS2 nanosheets on nanostructured metal phosphides for electrochemical applications. [ABSTRACT FROM AUTHOR]

The development of low‐cost electrocatalysts with excellent activity and durability for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) poses a huge challenge in water splitting. In this study, a simple and scalable strategy is proposed to fabricate 3 D heteronanorods on nickel foam, in which nickel molybdenum phosphide nanorods are covered with cobalt iron phosphide (P‐NM‐CF HNRs). As a result of the rational design, the P‐NM‐CF HNRs have a large surface area, tightly connected interfaces, optimized electronic structures, and synergy between the metal atoms. Accordingly, the P‐NM‐CF HNRs exhibit a remarkably high catalytic activity for the OER under alkaline conditions and wide‐pH HER. For overall water splitting, the catalyst only requires a voltage of 1.53 V to reach a current density of 10 mA cm−2 in 1 m KOH with prominent stability, and the activity is not degraded after stability testing for 36 h. This new strategy can inspire the design of durable nonprecious‐metal catalysts for large‐scale industrial water splitting. [ABSTRACT FROM AUTHOR]

A novel unsymmetrical covalent organic polymer, COP (1), was designed and characterized using several analytical and spectroscopic techniques. COP (1) was synthesized via the nucleophilic substitution reaction of 2,4,6-trichloro-1,3,5-triazine with p-amino phenol. Subsequently, COP (1) was immobilized with Pd(0) on its exterior and utilized as a heterogeneous catalyst (Pd@1). Pd@1 exhibited excellent catalytic activity and reusability for the Sonogashira C–C cross coupling reaction, and a few new products were synthesized. The confinement of Pd was well supported by the suitable functionalities present on the surface of COP (1). Furthermore, Pd@1 was used for eight consecutive catalytic runs without any considerable loss in its activity and no leaching of the metal NPs was observed. [ABSTRACT FROM AUTHOR]

Developing low‐cost and effective electrocatalysts for the hydrogen evolution reaction (HER) to replace Pt‐group metals is a continuous challenge. Recently, transition metal phosphides have received increasing attention owing to their high intrinsic activity in catalyzing HER in acidic media. Herein, we reported a novel hybrid nanostructure MoP/Co2P anchored on carbon fiber paper (CFP) (MoP/Co2P/CFP) which was achieved by a facile hydrothermal approach to obtain Co(CO3)0.35Cl0.20(OH)1.10 nanowires array (NA)/CFP, followed by deposition of MoO2 nanoparticles via chemical vapor deposition (CVD) in the presence of MoO3 and a subsequent in situ phosphorization process. It was worth noting that the catalyst exhibited higher catalytic activity for HER in 0.5 M H2SO4 solution, which afforded an overpotential of 140 mV at a current density of 10 mA cm−2, a Tafel slope of 80 mV dec−1, an exchange current density of 0.153 mA cm−2 and a high electrochemical double‐layer capacitance (Cdl) of 48.2 mF cm−2. Moreover, it also exhibited superior stability and durability in long‐term durability test. [ABSTRACT FROM AUTHOR]

The development of efficient and inexpensive bifunctional electrocatalysts with high activity and durability for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly desirable but challenging. Herein, we report the design and preparation of tungsten‐doped cobalt phosphide nanoneedle arrays on conductive carbon cloth (W−CoP/CC) as highly efficient and stable HER and OER electrocatalysts for overall water splitting. The nanoneedle array provides enriched active sites and facilitates ion diffusion and the 3D conductive CC skeleton enables fast charge transport. Moreover, tungsten doping improves the water adsorption ability, optimizes the hydrogen adsorption energy, and increases the electrochemical active surface area thereby resulting in much improved HER and OER catalytic activity. The W−CoP/CC composite shows low overpotentials of 32 mV at a current density of 10 mA cm−2 in 0.5 M H2SO4 electrolyte for HER and 77 and 252 mV in 1 M KOH solution for HER and OER, respectively, outperforming most previously reported metal phosphide electrocatalysts. The electrolyzer for overall water splitting with W−CoP/CC as both the anode and cathode achieves a stable current density of 10 mA cm−2 at a low cell voltage of 1.59 V with no obvious voltage change even after operation for 20 h. The results provide a new strategy to design and prepare high‐performance non‐noble metal phosphides for overall water splitting. [ABSTRACT FROM AUTHOR]

Transition metal phosphides (TMPs) are a promising catalyst material for the hydrogen evolution reaction (HER). In this study, we introduced inexpensive red phosphorus (P 4) into a homogeneous solution as a phosphorus source. Using the electrostatic spinning technique combined with high temperature carbonization, we successfully prepared self-supported carbon nanofibers doped with nitrogen (N) and loaded with ruthenium (Ru)-modified cobalt phosphide (Co 2 P) nanoparticles catalysts (Ru@Co 2 P/CNFs). The Ru@Co 2 P phosphide nanoparticles were evenly distributed on the surface of the carbon fibers, forming a three-dimensional network structure. The synergistic effect between the Ru and Co 2 P systems resulted in excellent catalytic activity and stability for the hydrogen evolution reaction in alkaline solutions. The N-doped conducting carbon matrix and large specific surface area of the active sites contributed to this enhanced performance. The Ru@Co 2 P/CNFs catalysts only required an overpotential of 48 mV at a current density of 10 mA cm−2, outperforming the noble metal platinum/carbon (Pt/C) catalysts, which required an overpotential of 52 mV. Furthermore, the Ru@Co 2 P nanoparticles were protected by a carbon layer, preventing catalyst corrosion during long-term operation. The HER performance of the Ru@Co 2 P/CNFs catalysts remained stable even after 40 h of continuous operation, demonstrating their long-lasting stability. This research introduces a new approach to developing cost-effective and highly active self-supported network-structured phosphide catalysts. • Anchoring Ru@Co 2 P nanoparticles on carbon substrates by electrostatic spinning and high-temperature carbonization techniques. • Ru@Co 2 P/CNFs showed excellent HER activity in alkaline media (η10 = 48 mV, 63.3 mV dec-1). • Ru@Co 2 P/CNFs showed excellent HER activity in alkaline media (η10 = 48 mV, 63.3 mV dec-1). • Carbon layer encapsulation and protection for enhanced conductivity and long-lasting stability. [ABSTRACT FROM AUTHOR]

Transition metal phosphides capture wide attention as electrocatalysts in lithium-sulfur (Li-S) batteries due to their unique electrocatalytic activity, and metal-organic framework (MOF) is well suited as precursor due to the inherent advantages such as structural/morphology diversity, tunable composition and distribution of internal elements. However, the relationship of the fabrication process, the phase and actual catalytic activity have been controversial. Herein, based on a facile morphological engineering of ZIF-67 (a classic MOF), three kinds of cobalt phosphide (polyhedron, cube and flake-like) are fabricated and different from traditional delicate strategies such as adopt surfactant and methanol to fabricate three-dimensional ZIF-67 (polyhedron or cube), two-dimensional flake ZIF-67 can be obtained just in aqueous solution without any agent. Besides, CoP/Co 2 P heterostructure is regularly induced although they are fabricated under the same condition, especially for flake cobalt phosphide. Furthermore, the flake cobalt phosphide exhibits improved redox reaction kinetics of polysulfides than that of other cobalt phosphides. After modifying commercial separator using the obtained flake cobalt phosphide, the Li-S battery exhibits a high initial capacity of 1253.6 mAh g−1 at 0.2 C and 858.7 mAh g−1 at 2 C. Meanwhile, the battery can also deliver a capacity of 1064.2 mAh g−1 even under a high sulfur loading of 4.0 mg cm−2. Furthermore, a capacity retention can reach 67.1% after 110 cycles. This work emphasizes the importance of morphology design of multifunctional catalysts for high performance Li-S battery. [Display omitted] • Three kinds of cobalt phosphides (polyhedron, flake and cube-like) are designed via a simple solution method. • Flake-like ZIF-67 facilitates to induce the formation of CoP/Co 2 P heterostructure. • F-cobalt phosphide can maximize the utilization of catalytic activity and enhance the deposition and decomposition of Li 2 S. [ABSTRACT FROM AUTHOR]

Nitrogen (N) species in biomass-based carbon can be adjusted through pyrolysis at different temperatures, optimizing the valence band structure of supported metal nanoparticles through electronic metal-support interactions (EMSIs). Herein, ginkgo leaves-based carbon supported cobalt phosphide (CoP@NSPC-T, T = 850, 900 and 950 °C) was obtained via carbothermal reduction method at different pyrolysis temperature. Pyridinic N and pyrrolic N in carbon lattice were dramatically decreased with pyrolysis temperature raised, whereas the graphitic N showed the opposite trend. The change in N species (pyridinic N, pyrrolic N and graphitic N) reconfigured the valence band structure of CoP@NSPC-T, inducing the enhancement of work function and the upshift of d-band center. A relationship between the ratio of (pyridinic N + pyrrolic N)/graphitic N, work function, d-band center, and HER activity (η 10) of catalysts was established. CoP@NSPC-900 with a moderate work function value and d-band center tend to achieve a balance for Volmer process and Heyrovsky process, exhibiting the lowest η 10 value activity among the resulted catalysts as the ratio of (pyridinic N + pyrrolic N)/graphitic N is 1.33. [Display omitted] • Nitrogen species in biomass derived carbon support is tuning by adjusting the pyrolysis temperature. • The impact of differ nitrogen species on the d-band center of CoP has been in-depth studied. • A relationship between nitrogen species, d-band center, work function and catalytic activity is finally established. [ABSTRACT FROM AUTHOR]

Novel alumina-supported cobalt phosphide catalysts (designated as CoP-3, CoP-10, CoP-20 and CoP-40) prepared from the precursors with Co loadings of 3, 10, 20 and 40 wt% by H2-temperature-programmed reaction were investigated as potential catalysts for preferential CO oxidation (PROX) in excess H2 at high temperatures. It was found that the catalytic activities of these Co2P/γ-Al2O3 catalysts were related to their Co loadings. The CoP-10 catalyst showed the best PROX performance in temperature range of 220–240 °C, which was attributed to its optimal microstructures (high surface area, small particle size and big amount of active site). [ABSTRACT FROM AUTHOR]

Development of robust and non-precious metal electrocatalysts for oxygen evolution reaction is central to sustainable electrochemical energy storage and conversion technologies. Self-reconstruction of electrocatalysts plays an important role during oxidation reactions. Exploring the correlation between the intrinsic electronic structures with the reconstruction in the layered metal thio (seleno) phosphates is highly expected but inadequate. In this paper, we report the uncovering of the surface self-reconstruction behavior of NiPS 3 nanosheets with remarkable electrochemical performance in an oxygen evolution reaction (OER). Our studies reveal that the orbital hybridization between S and P effectively modulates the surface electronic structure of Ni, lowering the Gibbs free energy of OH− adsorption and promoting the Ni2+ oxidation. As a result, this synergistic effect and the in-situ formed NiPS 3 –NiOOH heterostructure lead to impressive catalytic kinetic with a much small Tafel slope of 51 mV dec−1 and excellent stability in our as-synthesized NiPS 3 nanosheets. Our work provides fundamental understanding of the surface reconstruction of the promising metal thio (seleno) phosphates electrocatalysts toward OER from the view of intrinsic electronic structure. • Two dimensional NiPS 3 nanosheets were synthesized by CVD method. • Synergistic effect of S and P effectively modulates the electronic structure of Ni. • NiPS 3 –NiOOH heterostructures were in-situ formed due to self-reconstruction. • The NiPS 3 nanosheets exhibit superior catalytic activity for OER. [ABSTRACT FROM AUTHOR]

Fabricating and engineering heterointerface was an effective approach to improve electrochemical activity of catalysts through modulating their atomic arrangement and chemical states. Herein, cobalt phosphide and cobalt sulfide (CoP/CoSx) heterostructure hollow nanocones were fabricated by an in situ ion intercalation template‐assisted method. The microstructure of the heterointerface could be adjusted by changing the molar ratio of S/P. Electrochemical investigation revealed that the disordered structures at the heterointerface could influence the catalytic behavior of active sites. Rationally engineering the disordered structure could improve the electrocatalytic activity for oxygen and hydrogen evolution reactions (OER/HER). The optimized CoP/CoSx heterostructure exhibited favorable catalytic activity for OER, which delivered an overpotential at 10 mA cm−2 of 313 mV and a Tafel slope (93 mV dec−1) in alkaline media. Meanwhile, the optimized CoP/CoSx heterostructure also exhibited superior HER performance under acidic condition. [ABSTRACT FROM AUTHOR]

Abstract The development of high-efficiency nonprecious electrocatalysts based on inexpensive and earth abundant elements is of great significance for renewable energy technologies. Here, Co-tuned nickel phosphide electrocatalysts have been prepared by a facile co-precipitation, oxidation, and phosphidation method by regulating the atomic ratio of Co/Ni. Co species could modulate the electronic state behaviors of Ni x P y and the hierarchically nanostructured Ni/Co-P shows highly electrochemical activity with a small Tafel slope of 45 mV dec−1 and an overpotential of 148 mV to reach the current density of 10 mA cm−2 in 0.5 M H 2 SO 4 for hydrogen evolution reaction (HER). In 1.0 M KOH, an overpotential of 360 mV is required to achieve the current density of 10 mA cm−2 for oxygen evolution reaction (OER). Our research results suggest that doping metal is a useful route to improve the catalytic activity and our method may open up facile avenues to design other catalysts. Highlights • A facile and green method is developed to synthesize Co-tuned Ni x P y. • Doping Co alters the electronic state of Ni x P y and improves the catalytic activity. • The synergistic effect between Co and Ni may contribute to the catalytic activity. [ABSTRACT FROM AUTHOR]

Exploring efficient and durable catalysts derived from earth‐abundant and cost‐effective materials is a highly desirable route to overcome the sluggish anodic oxygen evolution reaction (OER). A series of multinary metal–organic gels (MOGs) with various and alterable metal element compositions are prepared by straightforward mixing of metal ions with ligand 4,4′,4′′‐[(1,3,5‐triazine‐2,4,6‐triyl)tris(azanediyl)]tribenzoic acid (H3TATAB) in solution at room temperature. Spinel‐type metal oxides with excellent electrocatalytic OER performance were then obtained through calcination of the as‐synthesized MOGs. In electrochemical testing, the trimetallic oxide CoFeNi‐O‐1 (derived from the MOG with a Co/Fe/Ni molar ratio of 5:1:4) exhibits remarkable catalytic activity with a low overpotential of 244 mV at a current density of 10 mA cm−2 and a small Tafel slope of 55.4 mV dec−1 in alkaline electrolyte, outperforming most recently reported electrocatalysts. This work not only provides a promising OER catalyst and enriches the application of MOGs in the catalytic field, but also offers a facile new route to acquiring multicomponent metal oxides with high electrocatalytic activity. [ABSTRACT FROM AUTHOR]

The growing hydrogen consumption has greatly promoted the development of efficient, stable and low-cost electrocatalysts for the hydrogen evolution reaction (HER). Constructing functional nanostructures is an efficacious strategy to optimize catalytic performance. Herein, we present a feasible route to fabricate distinctive 3D grass-like cobalt phosphide nanocones clad with mini-vesicles on the hierarchically porous Ni foam, which can directly serve as a binder-free electrocatalyst with superior catalytic activity and durability in HER. Thanks to its distinctive 3D microstructure featured with favourable pore-size distribution, abundant active sites provided by mini-vesicles and rapid electron transfer with the assistance of Ni foam, the as-grown grass-like CoP/NF electrocatalyst has shown a favourable overpotential in an acidic solution with an onset overpotential of ∼35 mV, an overpotential of 71 mV at a current density of 10 mA cm−2, reduced by 60 mV in comparison with that realized by urchin-like CoP/NF nanoprickles. Moreover, it has exhibited an excellent HER activity in the alkaline medium, with an overpotential of 117 mV at 10 mA cm−2, a Tafel slope of 63.0 mV dec−1 and a long-term electrochemical durability. Image 1 • Various CoP nanostructures including grass and urchin-like ones were prepared. • Porous g-CoP vesicles-decorated nanocones were grown on Ni-foam. • The mechanism on the formation of vesicles is investigated. • The as-prepared g-CoP/NF VDNCs exhibit excellent activities for HER. [ABSTRACT FROM AUTHOR]

Inorganic salts have been widely studied as templates for the synthesis of 2D layer structures. However, these salts normally can only serve as templates without any catalytic activity. Here, we report that LiCl used for the synthesis of ultrathin nanosheets not only serves as template for the synthesis of ultrathin Co2P nanosheets with a thickness of 0.7 nm but also acts as a catalyst that induces the phase‐transfer from CoP to Co2P. The Co2P nanosheets have a high electrochemical performance for oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

The development of highly active and stable electrocatalysts for the water splitting using the earth-abundant transition metal as precursor is important for the renewable energy application. Prussian blue analogues (PBAs) are regarded as an ideal precursor for the preparation of electrocatalysts because of its abundant metal elements and various derived porous nanostructures. In this work, the (NiCo)2P hollow nanocubes, which are firmly grown on Ni foam, are prepared by PBAs and used as an water splitting electrocatalyst with high activity and stability in 1 M KOH solution. Benefiting from the synergistic effect of nickel and cobalt, hollow structure and high double-layer capacitance, the as-synthesized (NiCo)2P/NF catalyst shows an excellent electrocatalytic performance for the water splitting. To achieve current density of 10 mA cm−2, for HER and OER, this material requires overpotentials of 162 mV and 220 mV, respectively. As an integrated electrocatalyst for water splitting, the (NiCo)2P/NF needs a cell voltage of 1.62 V to achieve current density of 10 mA cm−2. Furthermore, this material has long-term electrocatalytic stability (over 30 h). The high catalytic activity of this material is attributed to the synergistic effect of component and the hollow structure of catalyst. This facile and novel method of preparing bimetallic phosphide electrocatalysts with hollow structure provides a broadened space for the design and synthesis of non-noble metal catalysts in the future. [ABSTRACT FROM AUTHOR]

Herein, we report a hybrid electrocatalyst consisting of Ru clusters trapped in NiCo-layered double hydroxide (NiCo-LDH) as the basis for an efficient hydrogen evolution reaction (HER) in alkaline media. Benefiting from the fast water dissociation kinetics on NiCo-LDH and favorable H recombination on Ru, the resultant Ru-NiCo-LDH shows an extremely low HER overpotential of 28 mV at a current density of 10 mA cm−2 with a small Tafel slope of 42 mV dec−1. This superior catalytic activity can be ascribed to its high charge transfer ability and to the synergistic effect of the highly dispersed Ru and the NiCo-LDH. Moreover, we also found that the oxidized Ru incorporated in NiCo-LDH was entirely reduced to Ru0 under hydrogen-evolution conditions, which suggests that Ru0 is the true catalytically active phase responsible for the outstanding HER performance. • A Ru-NiCo-LDH catalyst was developed and exhibited very high HER activity of 28 mV at 10 mA cm−2. • The hybrid catalyst with rational design is proven to be effective toward HER in alkaline media. • The incorporated Ru species can be reduced into Ru0 during HER progress. [ABSTRACT FROM AUTHOR]

Rational design and fabrication of electrocatalysts with super-wetting interfaces is identified as an efficient strategy to enhance the catalytic performance for industrial water splitting. A simple and general electrodeposition strategy is proposed to synthesize self-supported Co-P films. SA as an additive can increase the P content in the deposited Co-P films with an optimized electronic structure and create a superaerophobic surface to accelerate the gas-releasing process under simulated industrial conditions. [Display omitted] • Self-supported Co-P films with tunable interfacial structure are fabricated. • SA as an additive can form Co-P films with high intrinsic catalytic activity. • SA-modified Co-P films exhibit superior HER performance at high-current–density. • Fabricated nanosheet arrays create a superaerophobic surface to accelerate the HER. • It offers a facile route to construct catalysts for practical water electrolysis. The exploration of earth-abundant and highly efficient catalysts for water electrolysis is vital for the sustainable development of future hydrogen economies but remains challenging. The rational construction of the special-interfacial structure is identified as one of the most efficient strategies to enhance the performance of water-electrolysis catalysts. Herein, cobalt phosphorus nanosheet arrays mediated by saccharin grown on copper foam (Co-P(SA)/CF) are rationally prepared via a facile one-step electrodeposition approach from a deep eutectic solvent (DES) consisting of choline chloride and ethylene glycol, known as Ethaline. Introducing SA increases the P content in the deposited Co-P composites with an optimized electronic structure and creates a superaerophobic surface to accelerate the hydrogen evolution reaction (HER). Such results significantly enhance the HER activity of Co-P(SA)/CF, requiring a small overpotential of 148.18 mV to drive 100 mA cm−2 in 1.0 M KOH. Impressively, Co-P(SA)/CF provides remarkable HER stability and can maintain 100 mA cm−2 over 165 h for continuous electrolysis operation in 6 M KOH at 80°C. Our work provides a promising avenue to regulate the interface super-wetting property of Co-P electrodes and offers a facile and efficient strategy for designing high-efficiency catalysts with superaerophobic surfaces for practical water electrolysis. [ABSTRACT FROM AUTHOR]

CoP nanotubes are synthesized through a nanoscale Kirkendall effect using Co(CO 3 ) 0.35 Cl 0.2 (OH) 1.10 nanorods as the cobalt source and template. CoP nanotubes and nanorods can be selectively synthesized by controlling the Co and P molar ratio in the phosphidation process, further confirming the diffusion controlled Kirkendall effect. Benefiting from the high surface area and improved mass and charge transportation, the CoP nanotubes exhibit higher hydrogen evolution catalytic activity than that of CoP nanorods and nanoparticles. The CoP nanotubes have a small onset potential of 55 mV for hydrogen evolution reaction, and high durability indicating by that the catalytic activity almost no change after 2000 cyclic voltammetry cycles. [ABSTRACT FROM AUTHOR]