Cation-Modulated HER and OER Activities of Hierarchical VOOH Hollow Architectures for High-Efficiency and Stable Overall Water Splitting

Atom-scale modulation of electronic regulation in nonprecious-based electrocatalysts is promising for efficient catalytic activities. Here, hierarchically hollow VOOH nanostructures are rationally constructed by partial iron substitution and systematically investigated for electrocatalytic water splitting. Benefiting from the hierarchically stable scaffold configuration, highly electrochemically active surface area, the synergistic effect of the active metal atoms, and optimal adsorption energies, the 3% Fe (mole ratio) substituted electrocatalyst (VOOH-3Fe) exhibits a low overpotential of 90 and 195 mV at 10 mA cm⁻² for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, respectively, superior than the other samples with a different substituted ratio. To the best of current knowledge, 195 mV overpotential at 10 mA cm⁻² is the best value reported for V or Fe (oxy)hydroxide-based OER catalysts. Moreover, the electrolytic cell employing the VOOH-3Fe electrode as both the cathode and anode exhibits a cell voltage of 0.30 V at 10 mA cm⁻² with a remarkable stability over 60 h. This work heralds a new pathway to design efficient bifunctional catalysts toward overall water splitting.