Phase Engineering of Dual Active 2D Bi2O3-based Nanocatalysts for Alkaline Hydrogen Evolution Reaction Electrocatalysis

Hydrogen evolution from electrochemical water splitting under alkaline conditions is an ongoing challenge for the requirement of a simultaneous balance to be achieved between the water dissociation step and the hydrogen adsorption on the catalysts. Herein, Bi2O3, an inactive catalyst for hydrogen evolution reaction (HER) aroused by its unfavourable hydrogen adsorption Gibbs free energy (ΔGH*), is activated by an in-situ phase engineering strategy for efficient HER electrocatalysis in alkaline media. Via this strategy, two-dimensional (2D) dual active Bi2O3 nanosheets with both BixNi alloy phases and α-Bi2O3 were fabricated to simultaneously catalyse the water dissociation step and the hydrogen formation step during the alkaline HER. In combining with the advantages of 2D nanomaterials and dual active catalytic sites, this phase engineered Bi2O3-based catalyst exhibited simultaneously accelerated water dissociation and optimized ΔGH* and thus excellent HER performance. The modulated catalyst demonstrated an overpotential of 127 mV (at j = 10 mA cm-2) and a Tafel slope of 92 mV dec-1 in 1 M KOH, which is exceptional compared with other Bi2O3-based HER electrocatalysts. This work not only provides an innovative way to activate HER-inferior bismuth oxide-based catalysts, but also offers new insights into the design of dual active catalysts for sluggish alkaline HER catalysis.