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Ngoc Quang Tran1 2 Quoc Viet Bui1 3 Hyoyoung Lee1 2 3

1, Sungkyunkwan University, Suwon, , Korea (the Republic of)
2, Sungkyunkwan University, Suwon, , Korea (the Republic of)
3, Sungkyunkwan University, Suwon, , Korea (the Republic of)

Sustainable development of high efficiency, cost-effective, and durable catalysts for hydrogen production from hydrogen evolution reaction (HER) using non-precious metal is urgent to tackle the global demand for renewable and clean alternative energy to help resolve the global warming issue. Up until now, an enormous amount of research on two-dimensional transition metal dichalcogenides, cubic pyrite-phase, and transition metal phosphides have been conducted as viable alternatives to platinum catalyst. In the past decade, considerable efforts have been dedicated to maximize the number of exposed active sites, facile charge transport, and optimize the free energy hydrogen adsorption, which are key factors that primarily contribute to the HER activity through anion or cation substitution. However, it is a great challenge to comply with all of the above-mentioned factors through only anion or cation substitutions, which results in inferior efficiency compared to the state-of-the-art Pt catalyst.
Motivated by this challenge, we reasoned that by anion-cation double substitutions in the cubic pyrite-phase, a synergistic effect may occur to satisfy all of the above-mentioned factors, which may enhance the overall performance of the HER activity. Here, we present the simultaneous incorporation of vanadium and phosphorus into the CoS2 moiety for preparing three-dimensional (3D) mesoporous cubic pyrite-metal Co1-xVxSP. We demonstrated that the higher catalytic activity of CoS2 after V incorporation can be primarily attributed to abundance active sites, whereas P substitution is responsible for improving HER kinetics and intrinsic catalyst. Interestingly, due to the synergistic effect of P-V double substitution, the 3D Co1-xVxSP shows superior electrocatalysts toward the HER with a very small overpotential of 55 mV at 10 mA cm-2, a small Tafel slope of 50 mVdec-1, and a high turnover frequency of 0.45 H2 s-1 at 10 mA cm-2, which is very close to commercial 20% Pt/C. Density functional theory (DFT) calculation reveals that the superior catalytic activity of the 3D Co1-xVxSP is contributed by the reduced the kinetic energy barrier of rate-determining HER step as well as the promotion of the desorption H2 gas process. Thus, the new Co1-xVxSP catalyst exhibits exceptional HER activity, which outperforms the current state-of-the-art catalysts, is one of the most promising candidates for effective non-precious metal electrocatalysts.

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