Canonic-Like HER Activity of Cr<sub>1-</sub> <sub>x</sub> Mo<sub>x</sub> B<sub>2</sub> Solid Solution: Overpowering Pt/C at High Current Density.
basic_science · Level V
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- Also identified by DOI 10.1002/adma.202000855.
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Abstract
Abundant transition metal borides are emerging as substitute electrochemical hydrogen evolution reaction (HER) catalysts for noble metals. Herein, an unusual canonic-like behavior of the c lattice parameter in the AlB<sub>2</sub> -type solid solution Cr<sub>1-</sub> <sub>x</sub> Mo<sub>x</sub> B<sub>2</sub> (x = 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1) and its direct correlation to the HER activity in 0.5 M H<sub>2</sub> SO<sub>4</sub> solution are reported. The activity increases with increasing x, reaching its maximum at x = 0.6 before decreasing again. At high current densities, Cr<sub>0.4</sub> Mo<sub>0.6</sub> B<sub>2</sub> outperforms Pt/C, as it needs 180 mV less overpotential to drive an 800 mA cm<sup>-2</sup> current density. Cr<sub>0.4</sub> Mo<sub>0.6</sub> B<sub>2</sub> has excellent long-term stability and durability showing no significant activity loss after 5000 cycles and 25 h of operation in acid. First-principles calculations have correctly reproduced the nonlinear dependence of the c lattice parameter and have shown that the mixed metal/B layers, such as (110), promote hydrogen evolution more efficiently for x = 0.6, supporting the experimental results.