Tuning Oxygen Vacancies in Co₃O₄ Nanorods through Solvent Reduction Method for Enhanced Oxygen Evolution Activity

Oxygen vacancies can act as active centers for oxygen evolution reaction (OER), thereby enhancing the electrocatalytic activity of the catalyst. Unfortunately, effective methods are rather limited to introducing a high amount of oxygen vacancies on the surface of nanocatalysts. Here, a facile solution reduction method has been demonstrated. By simply tuning the concentration of NaBH4 solution, we fabricate typical spinel Co3O4 nanorods with a reasonable density of oxygen vacancy defects and preserve the nanorod morphology and one-dimensional (1D) charge transport behavior of the starting material. As-prepared defect-rich Co3O4 nanorods show a low overpotential of 378 mV at a current density of 10 mA cm–2 and a small Tafel slope of 58.18 mV dec–1, and at the same time, its double-layer capacitance reaches 25.62 mF cm–2, which is nearly 4 times that of pristine Co3O4. The presence of oxygen vacancies makes the reduced Co3O4 possess excellent OER activity. It is worth noting that it still exhibits high stability even after 20 h of cycles of scanning under OER working conditions. This method is simpler, cheaper, and more environmentally friendly than the existing methods of preparing oxygen vacancies. This mild solution reduction method sheds light on the understanding of defect-based electrocatalysts, opening up a new route for developing highly efficient electrocatalysts for the OER.