Dynamic reconstruction regulation of α/β-CoMoO4 through phase engineering for enhanced alkaline water electrolysis

Abstract

Achieving exceptional bifunctional electrocatalytic activity toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media is imperative for sustainable hydrogen production. Herein, a novel α/β-CoMoO₄/CF self-supporting electrocatalyst was fabricated through a phase engineering strategy. Systematic ex situ characterizations and in situ electrochemical impedance spectroscopy measurement confirm that the combination of α and β phases regulates the electronic structure of β-CoMoO₄, accelerates the H₂O-adsorption/dissociation of the Volmer step for the HER, and promotes hydroxyl species deprotonation (OH⁻ activation) for the OER, achieving synchronous improvement of bifunctional reaction kinetics. Furthermore, in situ X-ray absorption fine structure (XAFS) spectroscopy and operando Raman spectroscopy verified that phase engineering accelerates the dynamic reconstruction response of α/β-CoMoO₄/CF for rapid conversion into active (oxy)hydroxide species in both the HER and OER, which serve as the real active sites. Benefiting from its optimized reaction kinetics and regulated reconstruction behavior, α/β-CoMoO₄/CF exhibits superior electrocatalytic performance, requiring overpotentials of only 197 and 364 mV to reach 500 mA cm⁻² for the HER and OER in 1.0 M KOH, respectively, and remarkably maintains stable operation for 1400 h. This work highlights the potential of phase engineering in promoting deep self-reconstruction of catalysts, providing a new paradigm for the development of high-efficiency transition metal oxide electrocatalysts.