Boosting hydrogen and oxygen evolution of porous CoP nanosheet arrays through electronic modulating with oxygen-anion-incorporation

Electrodeposition synthesis of cobalt-molybdenum bimetallic phosphide on nickel foam for efficient water splitting

A reasonable design of excellent bifunctional catalyst is an effective strategy for large-scale hydrogen production. In this study, a two-stage electrodeposition method was used to prepare a crystalline-amorphous structure cobalt molybdenum phosphide layered particles with different sizes on a nickel foam (NF) substrate. Electron rearrangement at the Co/CoMoP2@CoMoO4 heterogeneous interface can reduce the reaction energy barrier for HER and OER, and accelerate the catalytic reaction kinetics. The doping of Mo can promote the synergistic effect between Co and Mo, thereby optimizing the Gibbs free energy of hydrogen adsorption/desorption. This layered arrangement of different size particles greatly improves the active area of the catalyst. In alkaline solution, achieving a current density of 10 mA cm-2 only required overpotentials of 40 mV for HER and 278 mV for OER, respectively. The cell voltage required for the CoMo-P/NF||CoMo-P/NF electrolytic cell is only 1.53 V at 10 mA cm-2. This study provides a reference for the rapid, efficient, and environmentally friendly preparation of high-activity water splitting catalysts with large surface areas.

Strongly Coupled Heterostructured CoP/MoO2 as an Advanced Electrocatalyst for Urea-Assisted Water Electrolysis

Developing low-cost electrocatalysts with excellent activity and durability in urea-assisted water splitting is urgently needed in order to achieve sustainable hydrogen production. Herein, we in situ synthesized a robust coupled heterostructured electrocatalyst (CoP/MoO2) on a nickel foam (NF) substrate and explored its electrocatalytic performances in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and urea oxidation reaction (UOR). The overpotential of CoP/MoO2/NF is found to be only 11 mV at 10 mA cm-2 during the HER process, which is significantly lower than that of commercial Pt/C. Meanwhile, the UOR catalytic performance of CoP/MoO2/NF indicates fast reaction kinetics, along with a considerable low driving potential (1.26 V) compared to that of the OER (1.51 V). In situ and ex situ techniques demonstrate that these excellent electrocatalytic properties are mainly ascribed to the effective synergistic coupled effect and strong electronic interactions between single-component CoP and MoO2, which can tune electronic states of Co and Mo, expose more active sites, enhance intrinsic catalytic activity, and accelerate charge transfer. Moreover, when used in electrochemical overall water splitting and urea-assisted water electrolysis, CoP/MoO2/NF can reach a current density of 10 mA cm-2 at only 1.46 and 1.32 V. This outperforms Pt/C||RuO2 and numerous nonprecious metal electrocatalysts and maintains a stable long-term electrolytic operation for 84 h. This work provides a promising pathway for the development of efficient catalysts during urea-assisted water electrolysis for hydrogen production.

Aluminum-incorporation activates vanadium carbide with electron-rich carbon sites for efficient pH-universal hydrogen evolution reaction

Vanadium carbide (VC) is the greatest potential hydrogen evolution reaction (HER) catalyst because of its platinum-like property and abundant earth reserves. However, it exhibits insufficient catalytic performance due to the unfavorable interaction of reaction intermediates with catalysts. In this work, using NH4VO3 as the main raw material, the flow ratio of CH4 to Ar was accurately controlled, and a non-transition metal Al-doped into VC (100) nano-flowers with carbon hybrids on nickel foams (Al-VC@C/NF) was prepared for the first time as a high-efficiency HER catalyst by chemical vapor carbonization. The overpotential of Al-VC@C/NF catalysts in 0.5 M H2SO4 and 1 M KOH at a current density of 10 mA cm-2 are only 58 mV and 97 mV, respectively, which are the best HER performance among non-noble metal vanadium carbide based catalysts. Simultaneously, Al-VC@C/NF exhibits small Tafel slope (45 mV dec-1 and 73 mV dec-1) and excellent stability in acidic and alkaline media. Theoretical calculations demonstrate that doped Al atoms can induce electron redistribution on the vanadium carbide surface to form electron-rich carbon sites, which significantly reduces the energy barrier during the HER process. This work provides a new tactic to modulate vanadium-based carbons as efficient HER catalysts through non-transition metal doping.

Fabrication of ultra-stable and high-efficient CoP-based electrode toward seawater splitting at industrial-grade current density

The mild and rapid construction of economical, efficient and ultrastable electrodes for hydrogen production via water splitting at industrial-grade current density remains extremely challenging. Herein, a one-step mild electroless plating method is proposed to deposit cobalt phosphorus (CoP)-based species on robust nickel net (NN, denoted as Co-P@NN). The tight interfacial contact, corrosion-proof self-supporting substrate and synergistic effect of Co-P@Co-O contribute greatly to the rapid electron transport, high intrinsic activity and long-term durability in the alkaline simulated seawater (1.0 M KOH + 0.5 M NaCl). Attractively, Co-P@Co-O also achieves ultrastable catalysis for over 2880 h with negligible activity attenuation under various alkaline extreme conditions (simulated seawater, high-salt environment, domestic sewage and so on). Furthermore, this work successfully constructs a series of ternary elemental doped (Ni, S, B, Fe and so on) CoP-based catalytic electrodes for highly efficient overall seawater splitting (OSWS). This work demonstrates not only an ideal platform for the versatile strategy of mildly obtaining CoP-based electrocatalysts but also the pioneering philosophy of large-scale hydrogen production.

Self-Supporting Metal-Organic Framework-Based Nanoarrays for Electrocatalysis

The replacement of powdery catalysts with self-supporting alternatives for catalyzing various electrochemical reactions is extremely important for the large-scale commercial application of renewable energy storage and conversion technologies. Metal-organic framework (MOF)-based nanoarrays possess tunable compositions, well-defined structure, abundant active sites, effective mass and electron transport, etc., which enable them to exhibit superior electrocatalytic performance in multiple electrochemical reactions. This review presents the latest research progress in developing MOF-based nanoarrays for electrocatalysis. We first highlight the structural features and electrocatalytic advantages of MOF-based nanoarrays, followed by a detailed summary of the design and synthesis strategies of MOF-based nanoarrays, and then describe the recent progress of their application in various electrocatalytic reactions. Finally, the challenges and perspectives are discussed, where further exploration into MOF-based nanoarrays will facilitate the development of electrochemical energy conversion technologies.

Hierarchically structured nickel/molybdenum nitride heterojunctions as superior bifunctional electrodes for overall water splitting

A 3D hierarchical heterostructure of intermetallic compound heterojunctions is first rationally designed and presented as a highly-active bifunctional electrode for water splitting.