Porous Co3O4/CoS2 nanosheet-assembled hierarchical microspheres as superior electrocatalyst towards oxygen evolution reaction

Abstract Developing high-efficiency electrocatalysts based on non-precious transition metal compounds alternative to noble metal for oxygen evolution reaction (OER) is crucial for renewable energy storage technologies. Herein we designed a novel OER electrocatalyst by incorporating transition metal oxide (TMO) and sulfide (TMS) into a hierarchical nanoporous structure. Hierarchical porous Co3O4 nanosheet-assembled microspheres (HPMS Co3O4) were fabricated by a facile solvothermal method followed by an annealing process, and the Co3O4/CoS2 composite was easily obtained by a simple subsequent sulfurization process, which maintained the HPMS structure. Due to rapid surface diffusion and mass transfer, increased active sites, improved conductivity and strong synergetic coupling effects, the prepared HPMS Co3O4/CoS2 composite showed significantly enhanced electrocatalytic OER activities with a current density of 10 mA cm−2 at a low overpotential of 280 mV, a small Tafel slope of about 63 mV dec−1 and satisfactory stability at 20 mA cm−2. Notablely, it was non-durable at high current density. We expect that more active TMS functionalized hierarchical porous TMO will open a new avenue to innovate non-precious OER electrocatalysts.