Aldehyde reduced Co₃O₄ to form oxygen vacancy and enhance the electrochemical performance for oxygen evolution reaction and supercapacitors

Oxygen vacancy is a feasible approach to boost the electrochemical properties for metal oxides. In this work, a Co₃O₄ with abundant oxygen vacancy is synthesized via aldehyde reduction. After the procedure, the reduced Co₃O₄ exhibits larger electrochemical active surface areas and better electrical conductivity. These outstanding characteristics can improve its performance of catalytic and energy storage. As for catalyst of oxygen evolution reaction, the reduced Co₃O₄ delivers a smaller potential of 1.55 V versus the reversible hydrogen electrode to realize a current density of 10 mA cm⁻² and a lower Tafel slope of 71 mV dec⁻¹ in alkaline solution, and these values are smaller than those of pristine Co₃O₄. Especially the reduced Co₃O₄ possesses superior stability: the measurements of the polarization curves before and after 15h of stability tests basically coincide. In a supercapacitor, the positive electrode of reduced Co₃O₄ achieves about 1.7 times areal capacitance of pristine Co₃O₄ at current density of 1 mA cm⁻². Significantly, the superior cycling stability is still retained. Also, an aqueous asymmetric supercapacitor is assembled to evaluate the energy storage performance of the R-Co₃O₄. Moreover, the oxygen vacancy formation strategy for Co₃O₄ may be generally extended to other metal oxides for application in energy storage and conversion. (paper)