Fe-doping-induced cation substitution and anion vacancies promoting Co3O4 hexagonal nanosheets for efficient overall water splitting

Water electrolysis is a green technology for hydrogen fuel production, but greatly hampered by the slow kinetics of the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER). In this work, we report an efficient strategy to simultaneously promote OER and HER performance on Co3O4 hexagonal nanosheets via Fe-doping-induced cation substitution and anion vacancies. Benefiting from the integrated advantages of well-defined ultrathin nanosheets, abundant vacancies, and unique three-dimensional electrode configuration, the optimized Fe-doped Co3O4 hexagonal nanosheets/nickel foam (Fe0.4Co2.6O4 HNSs/NF) can achieve overpotentials of 328 mV at 100 mA cm−2 for OER and 315 mV at 500 mA cm−2 for HER, respectively, which is comparable to those of the benchmark noble electrocatalysts. More importantly, the Fe0.4Co2.6O4 HNSs/NF-assembled electrolyzer for overall water splitting can deliver a current density of 100 mA cm−2 at a cell voltage as low as 1.66 V and work steadily at 50 mA cm−2 with a negligible fading up to 140 h.