Development of non-noble metal electrocatalysts for hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) in acid is a great challenge for the development of polymer electrolyte membrane water electrolysis (PEMWE) and polymer electrolyte membrane fuel cells (PEMFC). Here, we report an efficient strategy for modulating the electron density of MoO2 by Ni doping to accelerate HER and HOR in acid. This is particularly important for PEMWE, PEMFC, and regenerative fuel cells. X-ray absorption spectroscopy demonstrates that Ni is doped by replacing Mo atoms in MoO2. Then Ni doping can lead to electron deficiency on neighboring O sites, which are induced to adsorb hydrogen and then increase the surface hydrogen coverage. Therefore, the doping of Ni can modulate the electron density of MoO2 for accelerating HER and HOR. Our results indicate that the incorporation of a high-electronegativity transition metal into MoO2 provides a new strategy for replacing Pt as an electrocatalyst for HER and HOR in acid.

Transition metal nitrides and elemental doping are effective methods to enhance the catalytic activity of hydrogen evolution reaction (HER) at a high current density. Herein, Ni-W2N@NF was synthesized to exhibit excellent HER performance in an alkaline environment. Not only theoretical but also experimental analyses prove that Ni enters the W2N lattice in the form of substitutional doping. Ni-doped W2N optimizes the free energy of hydrogen adsorption and hydroxide adsorption. Thus, the HER kinetics are accelerated. Therefore, the synthesized Ni-W2N@NF achieved an industrial high current density of 2000 mA cm–2 in 1 M KOH with a small overpotential of 317 mV. The HER activity of Ni-W2N@NF is superior to those of most reports. What is more, the obtained catalyst achieves a current density of 1500 mA cm–2 in an alkaline seawater solution with an overpotential of only 345 mV and exhibits excellent cycling stability. This work will offer a feasible idea for a designing platinum group metals free metal as an effective catalyst for HER reaction under an industrial large current in an alkaline solution.

Hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) have aroused great interest, but the high price of platinum group metals (PGMs) limits their development.The electronic reconstruction at the interface of a heterostructure is a promising strategy to enhance their catalytic performance. Here, MoO 2 /Ni heterostructure was synthesized to provide effective HER in an alkaline electrolyte and exhibit excellent HOR performance. Theoretical and experimental analyses prove that the electron density around the Ni atom is reduced. The electron density modulation optimizes the hydrogen adsorption and hydroxide adsorption free energy, which can effectively improve the activity of both HER and HOR. Accordingly, the prepared MoO 2 /Ni@NF catalyst reveals robust HER activity (η 10 = 50.48 mV) and HOR activity (j 0 = ∼1.21 mA cm −2 ). This work demonstrates an effective method to design heterostructure interfaces and tailor the surface electronic structure to improve HER/HOR performance.

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