water splitting techniques, however, large energy consumption in AWE and the use of noble-metal based catalysts in PEM electrolyzers prohibited the wide application of these water electrolysis techniques. Anion exchange membrane (AEM) water electrolyzer combines the merits of AWE and PEM electrolyzers, and is regarded as a promising future water electrolysis technology with notable advantages, including the simple and compact structure and the use of earth-abundant transition metal catalysts. [2,3] However, the development of the AEM electrolyzer is still in its infancy to date. Developing high-efficient and stable electrocatalysts is highly required to improve the current density and energy efficiency of the AEM water electrolyzer.Between the two half-cell reactions in the AEM water electrolyzer, hydrogen evolution reaction (HER) is more challenging in alkaline media due to its sluggish kinetics. The additional water dissociation step to generate proton (H*) sources results in 2-3 orders of lower activity than that in the PEM electrolyzer. [4] Various transition metal (TM)based materials have been developed in recent years to improve HER activity in alkaline media, including TM sulfides, [5,6] selenides, [7,8] and phosphides. [9][10][11][12] In particular, nickel phosphides have attracted great attention due to their high electronic conductivity and structural diversity. However, pure-phase metal phosphides have relatively large absolute values of Gibbs free Regulating the electronic structure and intrinsic activity of catalysts' active sites with optimal hydrogen intermediates adsorption is crucial to enhancing the hydrogen evolution reaction (HER) in alkaline media. Herein, a heterostructured V-doped Ni 2 P/Ni 12 P 5 (V-Ni 2 P/Ni 12 P 5 ) electrocatalyst is fabricated through a hydrothermal treatment and controllable phosphidation process. In comparison with pure-phase V-Ni 2 P, in/ex situ characterizations and theoretical calculations reveal a redistribution of electrons and active sites in V-Ni 2 P/Ni 12 P 5 due to the V doping and heterointerfaces effect. The strong coupling between Ni 2 P and Ni 12 P 5 at the interface leads to an increased electron density at interfacial Ni sites while depleting at P sites, with V-doping further promoting the electron accumulation at Ni sites. This is accompanied by the change of active sites from the anionic P sites to the interfacial Ni-V bridge sites in V-Ni 2 P/Ni 12 P 5 . Benefiting from the interface electronic structure, increased number of active sites, and optimized H-adsorption energy, the V-Ni 2 P/Ni 12 P 5 exhibits an overpotential of 62 mV to deliver 10 mA cm -2 and excellent long-term stability for HER. The V-Ni 2 P/Ni 12 P 5 catalyst is applied for anion exchange membrane water electrolysis to deliver superior performance with a current density of 500 mA cm -2 at a cell voltage of 1.79 V and excellent durability.
Developing low‐cost and high‐performance transition metal‐based electrocatalysts is crucial for realizing sustainable hydrogen evolution reaction (HER) in alkaline media. Here, a cooperative boron and vanadium co‐doped nickel phosphide electrode (B, V‐Ni2P) is developed to regulate the intrinsic electronic configuration of Ni2P and promote HER processes. Experimental and theoretical results reveal that V dopants in B, V‐Ni2P greatly facilitate the dissociation of water, and the synergistic effect of B and V dopants promotes the subsequent desorption of the adsorbed hydrogen intermediates. Benefiting from the cooperativity of both dopants, the B, V‐Ni2P electrocatalyst requires a low overpotential of 148 mV to attain a current density of −100 mA cm−2 with excellent durability. The B, V‐Ni2P is applied as the cathode in both alkaline water electrolyzers (AWEs) and anion exchange membrane water electrolyzers (AEMWEs). Remarkably, the AEMWE delivers a stable performance to achieve 500 and 1000 mA cm−2 current densities at a cell voltage of 1.78 and 1.92 V, respectively. Furthermore, the developed AWEs and AEMWEs also demonstrate excellent performance for overall seawater electrolysis.
Electrocatalytic CO2 to CO conversion is approaching the industrial benchmark. Currently, Au electrodes show the best performance, whereas non-precious metal catalysts exhibit inferior activity. Here we show a densely populated Ni single-atom on nanoparticle catalyst (NiSA/NP) via direct solid-sate pyrolysis, where Ni nanoparticles donate electrons to Ni(i)-N-C sites via carbon nanotubes network, achieves a high CO current of 352 mA cm−2 at -0.55 V vs RHE in an alkaline flow cell. When coupled with a NiFe-based oxygen evolution anode into a zero-gap membrane electrolyser, it delivers an industrial-relevant CO current of 310 mA cm−2 at a low cell voltage of -2.3 V, corresponding to an overall energy efficiency of 57%. The superior CO2 electroreduction performance is attributed to the enhanced adsorption of key intermediate COOH* on electron-rich Ni single atom, together with the dense active sites.
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