Plasma-induced Mo-doped Co3O4 with enriched oxygen vacancies for electrocatalytic oxygen evolution in water splitting

Heteroatomic substitution and vacancy engineering of spinel oxides can theoretically optimize the oxygen evolution reaction (OER) through charge redistribution and d-band center modification but still remain a great challenge in both the preparation and catalytic mechanism. Herein, we proposed a novel and efficient Ar-plasma (P)-assisted strategy to construct heteroatom Mo-substituted and oxygen vacancies enriched hierarchical spinel Co3O4 porous nanoneedle arrays in situ grown on carbon cloth (denoted P-Mo-Co3O4@CC) to improve the OER performance. Ar-plasma technology can efficiently generate vacancy sites at the surface of hydroxide, which induces the anchoring of Mo anion salts through electrostatic interaction, finally facilitating the substitution of Mo atoms and the formation of oxygen vacancies on the Co3O4 surface. The P-Mo-Co3O4@CC affords a low overpotential of only 276 mV at 10 mA cm(-2) for the OER, which is 58 mV superior to that of Mo-free Co3O4@CC and surpasses commercial RuO2 catalyst. The robust stability and satisfactory selectivity (nearly 100% Faradic efficiency) of P-Mo-Co3O4@CC for the OER are also demonstrated. Theoretical studies demonstrate that Mo with variable valance states can efficiently regulates the atomic ratio of Co3+/Co2+ and increases the number of oxygen vacancies, thereby inducing charge redistribution and tuning the d-band center of Co3O4, which improve the adsorption energy of oxygen intermediates (e.g., *OOH) on P-Mo-Co3O4@CC during OER. Furthermore, the two-electrode OER//HER electrolyzer equipped with P-Mo-Co3O4@CC as anode displays a low operation potential of 1.54 V to deliver a current density of 10 mA cm(-2), and also exhibits good reversibility and anticurrent fluctuation ability under simulated real energy supply conditions, demonstrating the great potential of P-Mo-Co3O4@CC in water electrolysis.

Automated summary

By employing an Ar-plasma-assisted strategy, a new type of hierarchical spinel Co3O4 porous nanoneedle arrays with Mo substitution and oxygen vacancies were prepared and demonstrated superior performance for the oxygen evolution reaction (OER). The Mo substitution and oxygen vacancy formation were achieved through charge redistribution and d-band center modification. The resulting material, denoted P-Mo-Co3O4@CC, exhibited a low overpotential and high stability, making it a promising catalyst for water electrolysis.