Phase engineering of dual active 2D Bi2O3-based nanocatalysts for alkaline hydrogen evolution reaction electrocatalysis

Abstract

In electrochemical water splitting, the balance between water dissociation step and the hydrogen adsorption on the catalysts is an ongoing challenge. Herein, Bi₂O₃, an inactive catalyst for the hydrogen evolution reaction (HER) caused by its unfavourable hydrogen adsorption Gibbs free energy (ΔG_H*), is activated by an in situ phase engineering strategy for efficient HER electrocatalysis in alkaline media. Through this strategy, two-dimensional (2D) dual active Bi₂O₃ nanosheets with both Bi_xNi alloy phases and α-Bi₂O₃ were fabricated to simultaneously catalyse the water dissociation step and the hydrogen formation step during an alkaline HER. In combination with the advantages of 2D nanomaterials and dual active catalytic sites, this phase engineered Bi₂O₃-based catalyst exhibited much improved alkaline 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, and is exceptional compared with other Bi₂O₃-based HER electrocatalysts. This work not only provides an innovative way to activate HER-inferior bismuth-based catalysts, but also offers new insights into the design of dual active catalysts for sluggish alkaline HER catalysis.