Reduced graphene oxide supported zinc/cobalt oxide nanoparticles as highly efficient electrocatalyst for oxygen evolution reaction

• TRGO@ZnO/Co 3 O 4 was synthesized via sol–gel and chemical wet routes for OER. • Catalyst exhibited low overpotential (160 mV) and small tafel slope (50 mV/dec). • Demonstrated improved electrical conductivity and small charge transfer resistance. • It exhibited enhanced electrochemically effective surface area. • Exhibited excellent stability and durability in acidic media. Developing novel electrocatalysts with both high efficiency and low cost are highly needed for the oxygen evolution reaction (OER). In this work, self-assembled cobalt oxide (Co 3 O 4 ) and zinc oxide (ZnO) nanoparticles on thermally reduced graphene oxide (TRGO) were successfully synthesized via simple chemical wet, sol–gel, and thermal routes as highly efficient electrocatalysts for the OER in acidic media. The synthesized TRGO@ZnO/Co 3 O 4 catalyst presents improved OER performance, owing to the TRGO, which acted as a conducting support in the synthesized catalyst. The catalyst exhibited a low ovepotential of 160 mV at a current density of 10 mA cm −2 and a small Tafel slope of 50 mV dec -1 , which is much smaller than that of pristine Co 3 O 4 and TRGO. The specific activity and turnover frequency of the optimal catalyst at an overpotential of 400 mV were 0.334 mA cm −2 and 2.891 s −1 , respectively, which are considerably higher than those of pristine Co 3 O 4 (0.102 mA cm −2 , 0.088 s −1 ) and ZnO/Co 3 O 4 (0.063 mA cm −2 , 0.109 s −1 ). In addition, it exhibited excellent stability and initial catalytic activity remained at 89% after a long time of 50 h at 10 mA cm −2 with faradaic efficiency of 95.34%. Thus, the synthesized TRGO@ZnO/Co 3 O 4 catalyst material can be a promising candidate material to replace the expensive noble metal as an OER catalyst.