Transition metal sulfides are promising non-noble metal catalysts for water oxidation, a vital half reaction of electrocatalytic water splitting. However, the realization of tunable electronic structure and synergetic catalysis of cobalt sulfides is still a challenge. In this work, a salt-templating route was adopted to embed uniform Co9S8 nanoparticles into high-conductive N, S co-doped carbon nanosheets (Co9S8/N,S-CNs). Benefiting from the abundant catalytic active sites and optimized electronic structure, the as-prepared Co9S8/N,S-CNs exhibited high efficiency with a low overpotential of 325 mV to afford current density of 10 mA cm(-2) and low Tafel slope of 86.3 mV dec(-1) towards oxygen evolution in 1 M KOH alkaline electrolyte.