Electron-transfer enhanced MoO2-Ni heterostructures as a highly efficient pH-universal catalyst for hydrogen evolution

Electron transfer enhanced flower-like NiP2-Mo8P5 heterostructure synergistically accelerates fast HER kinetics for large-current overall water splitting

Developing an innovative metal-phosphorus heterostructure as an excellent electrocatalyst for hydrogen evolution reaction (HER) is crucial for achieving large-scale water electrolysis, although it remains challenging. Herein, we introduce a pioneering strategy entailing the coordination of two metal phosphides in a catalytic structure by employing a wide variety of catalytically active species and regulating the electronic structure. Our method involves an extraordinary heterostructure construction with nickel phosphide and molybdenum phosphide formed on nickel foam (NiP2-Mo8P5@NF) through a controlled-solvent thermal and low-temperature phosphorization strategy. Experiments disclose that heterostructure of nickel and molybdenum can effectively modulate the electronic structure of the metal center, foster a robust electronic interaction between Ni and Mo, and induce the formation of rich active sites. The resulting benefits include improved electrical conductivity, which is conducive to synergistically enhancing the electrocatalytic efficiency. Moreover, the NiP2-Mo8P5@NF achieves superhydrophilicity, ensuring effective electrolyte contact and accelerating reaction kinetics. Consequently, NiP2-Mo8P5@NF exhibits favorable HER performance and long-term stability, outperforming commercial Pt/C and most other contemporary electrocatalysts. In practical application, the overall water splitting device with NiP2-Mo8P5@NF as cathode delivers a low cell voltage and demonstrates noteworthy durability. This will pave the way for its prospective adoption in industrial water electrolysis applications.

Heterogeneous-Interface-Enhanced Adsorption of Organic and Hydroxyl for Biomass Electrooxidation

Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) provides an efficient way to obtain high-value-added biomass-derived chemicals. Compared with other transition metal oxides, CuO exhibits poor oxygen evolution reaction performance, leading to high Faraday efficiency for HMF oxidation. However, the weak adsorption and activation ability of CuO to OH^- species restricts its further development. Herein, the CuO-PdO heterogeneous interface is successfully constructed, resulting in an advanced onset-potential of the HMF oxidation reaction (HMFOR), a higher current density than CuO. The results of open-circuit potential, in situ infrared spectroscopy, and theoretical calculations indicate that the introduction of PdO enhances the adsorption capacity of the organic molecule. Meanwhile, the CuO-PdO heterogeneous interface promotes the adsorption and activation of OH^- species, as demonstrated by zeta potential and electrochemical measurements. This work elucidates the adsorption enhancement mechanism of heterogeneous interfaces and provides constructive guidance for designing efficient multicomponent electrocatalysts in organic electrocatalytic reactions.

Engineering cobalt nitride nanosheet arrays with rich nitrogen defects as a bifunctional robust oxygen electrocatalyst in rechargeable Zn-air batteries

Developing high-activity bifunctional oxygen electrocatalysts to overcome the sluggish 4e^- kinetics is an urgent challenge for rechargeable metal-air batteries. Here, we prepared a CoN nanosheet catalyst with rich nitrogen defects (CoN-N_d) through solvothermal and low-temperature nitridation. Notably, the study finds for the first time that only Co LDH materials can be mostly converted to CoN-N_d under the same nitriding conditions relative to different Co-based precursors. Experiments indicate that the constructed CoN-N_d catalyst exhibits preeminent electrocatalytic activities for both oxygen evolution reaction (η₁₀ = 243 mV) and oxygen reduction reaction (J_L = 5.2 mA cm^-2). Moreover, the CoN-N_d-based Zinc-air battery showed a large power density of 120 mW cm^-2 and robust stability over 260 cycles, superior to the state-of-art Pt/C + RuO₂. The superior performance is attributed to a large number of defects formed by the disordered arrangement of local atoms on the catalyst that facilitate the formation of more active sites, and alternate array-like structures thereof improving electrolyte diffusion and gas emission.

Plasma Engineering of Basal Sulfur Sites on MoS2 @Ni3 S2 Nanorods for the Alkaline Hydrogen Evolution Reaction

Inexpensive and efficient catalysts are crucial to industrial adoption of the electrochemical hydrogen evolution reaction (HER) to produce hydrogen. Although two-dimensional (2D) MoS2 materials have large specific surface areas, the catalytic efficiency is normally low. In this work, Ag and other dopants are plasma-implanted into MoS2 to tailor the surface and interface to enhance the HER activity. The HER activty increases initially and then decreases with increasing dopant concentrations and implantation of Ag is observed to produce better results than Ti, Zr, Cr, N, and C. At a current density of 400 mA cm-2 , the overpotential of Ag500-MoS2 @Ni3 S2 /NF is 150 mV and the Tafel slope is 41.7 mV dec-1 . First-principles calculation and experimental results reveal that Ag has higher hydrogen adsorption activity than the other dopants and the recovered S sites on the basal plane caused by plasma doping facilitate water splitting. In the two-electrode overall water splitting system with Ag500-MoS2 @Ni3 S2 /NF, a small cell voltage of 1.47 V yields 10 mA cm-2 and very little degradation is observed after operation for 70 hours. The results reveal a flexible and controllable strategy to optimize the surface and interface of MoS2 boding well for hydrogen production by commercial water splitting.

Smart Designs of Mo Based Electrocatalysts for Hydrogen Evolution Reaction

As a sustainable and clean energy source, hydrogen can be generated by electrolytic water splitting (i.e., a hydrogen evolution reaction, HER). Compared with conventional noble metal catalysts (e.g., Pt), Mo based materials have been deemed as a promising alternative, with a relatively low cost and comparable catalytic performances. In this review, we demonstrate a comprehensive summary of various Mo based materials, such as MoO2, MoS2 and Mo2C. Moreover, state of the art designs of the catalyst structures are presented, to improve the activity and stability for hydrogen evolution, including Mo based carbon composites, heteroatom doping and heterostructure construction. The structure–performance relationships relating to the number of active sites, electron/ion conductivity, H/H2O binding and activation energy, as well as hydrophilicity, are discussed in depth. Finally, conclusive remarks and future works are proposed.

Nanowire-structured FeP-CoP arrays as highly active and stable bifunctional electrocatalyst synergistically promoting high-current overall water splitting

The design and construction of highly efficient and durable non-noble metal bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media is essential for developing the hydrogen economy. To achieve this goal, we have developed a bifunctional nanowire-structured FeP-CoP array catalyst on carbon cloth with uniform distribution through in-situ hydrothermal growth and phosphating treatment. The unique nanowire array structure and the strong electronic interaction between FeP and CoP species have been confirmed. Electrochemical studies have found that the designed Fe_0.14Co_0.86-P/CC catalyst appears excellent HER (130 mV@10 mA cm^-2)/OER (270 mV@10 mA cm^-2) activity and stability. Moreover, the bifunctional Fe_0.14Co_0.86-P/CC^(+/-) catalyst is also used in simulated industrial water splitting system, where the pair catalyst requires about 1.95 and 2.14 V to reach 500 and 1000 mA cm^-2, even superior to the control RuO₂⁽⁺⁾||Pt/C^(-) catalyst, showing good industrial application prospects. These excellent electrocatalytic properties are attributed to the synergy between FeP and CoP species as well as the unique microstructure, which can accelerate charge transfer, expose more active sites and enhance electrolyte diffusion and gas emissions.

Interface Engineering of Needle-Like P-Doped MoS2 /CoP Arrays as Highly Active and Durable Bifunctional Electrocatalyst for Overall Water Splitting

Developing a bifunctional water splitting catalyst with high efficiency and low cost are crucial in the electrolysis water industry. Here, we report a rational design and simple preparation method of MoS₂ -based bifunctional electrocatalyst on carbon cloth (CC). The optimized P-doped MoS₂ @CoP/CC catalyst presents low overpotentials for the hydrogen (HER) and oxygen evolution reactions (OER) of 64 and 282 mV in alkaline solution as well as 72 mV HER overpotential in H₂ SO₄ at a current density of 10 mA cm^-2 . Furthermore, P-MoS₂ @CoP/CC as a bifunctional catalyst delivered relatively low cell voltages of 1.83 and 1.97 V at high current densities of 500 and mA cm^-2 in 30 % KOH. The two-electrode system showed a remarkable stability for 30 h, even outperformed the benchmark RuO₂ ||Pt/C catalyst. The excellent electrochemical performance can be credited to the unique microstructure, high surface area, and the synergy between metal species. This study presents a possible alternative for noble metal-based catalysts to overcome the challenges of industrial applications.

Metal-Organic Framework (MOF)-Derived Electron-Transfer Enhanced Homogeneous PdO-Rich Co3 O4 as a Highly Efficient Bifunctional Catalyst for Sodium Borohydride Hydrolysis and 4-Nitrophenol Reduction

Developing a bifunctional catalyst with low cost and high catalytic performance in NaBH₄ hydrolysis for H₂ generation and selective reduction of nitroaromatics will make a significant impact in the field of sustainable energy and water purification. Herein, a low-loading homogeneously dispersed Pd oxide-rich Co₃ O₄ polyhedral catalyst (PdO-Co₃ O₄ ) with concave structure is reported by using a metal-organic framework (MOF)-templated synthesis method. The results show that the PdO-Co₃ O₄ catalyst has an exceptional turnover frequency (3325.6 mol_H2  min^-1  mol_Pd ^-1 ), low activation energy (43.2 kJ mol^-1 ), and reasonable reusability in catalytic H₂ generation from NaBH₄ hydrolysis. Moreover, the optimized catalyst also shows excellent catalytic performance in the NaBH₄ selective reduction of 4-nitrophenol to 4-aminiphenol with a high first-order reaction rate of approximately 1.31 min^-1 . These excellent catalytic properties are mainly ascribed to the porous concave structure, monodispersed Pd oxide, as well as the unique synergy between PdO and Co₃ O₄ species, which result in a large specific surface area, high conductivity, and fast solute transport and gas emissions.

Molybdenum-tungsten Oxide Nanowires Rich in Oxygen Vacancies as An Advanced Electrocatalyst for Hydrogen Evolution

Electrolysis of water is a promising way to produce hydrogen fuel in large scale. The commercialization of this technology requires highly efficient non-noble metal electrocatalysts to decease the energy input for the hydrogen evolution reaction (HER). In this work, a novel nanowire structured molybdenum-tungsten bimetallic oxide (CTAB-D-W₄ MoO₃ ) is synthesized by a simple hydrothermal method followed with post annealing treatment. The obtained metal oxides feature with enhanced conductivity, rich oxygen vacancies and customized electronic structure. As such, the composite electrocatalyst exhibits excellent electrocatalytic performance for HER in an acidic environment, achieving a large current density of 100 mA cm^-2 at overpotential of only 286 mV and a small Tafel slope of 71.2 mV dec^-1 . The excellent electrocatalytic HER performance of CTAB-D-W₄ MoO₃ is attributed to the unique nanowire structure, rich catalytic active sites and promoted electron transfer rate.