O22-/O- functionalized oxygen-deficient Co3O4 nanorods as high performance supercapacitor electrodes and electrocatalysts towards water splitting

Owing to high theoretical specific capacitance of 3560 F g(-1) and intrinsic activity towards oxygen evolution reaction (OER), inexpensive Co3O4 is drawing much attention as either a promising pseudocapacitive electrode or OER catalyst. However, restricted to poor conductivity and lack of active sites, Co3O4 usually exhibits limited experimental capacitance and OER activity, barely satisfying high energy density delivering of supercapacitors and low energy input of water-splitting systems. Herein, we report O-2(2-)/O- functionalized oxygen-deficient Co3O4 nanorods for supercapacitor and water splitting dual applications. The CoC2O4 center dot 2H(2)O converted oxygen-deficient Co3O4 nanorods show enhanced electrical conductivity as confirmed by the increased carrier density. The increased number of Co2+ sites (oxygen vacancies) and CoOOH are believed to contribute to the improvement in faradaic reactions and OER activity. Additionally, surface functionalization by O-2(2-)/O- is realized in oxygen-deficient Co3O4 nanorods. On the basis of these merits, the as-synthesized Co3O4 nanorods demonstrate a significantly high specific capacitance of 739 F g(-1) and an ultralow overpotential of 275 mV at 10 mA cm(-2) for OER with ultralong stability of over 300 h (@ 100 mA cm(-2)). Specifically, an electrolyzer for overall water splitting can be driven by asymmetric supercapacitors with the optimized cobalt oxide as both electrocatalyst and electrode material.