Sodium chloride modulated construction of hollow Co/Co3O4 heterostructure with enhanced mesoscale diffusion towards overall water splitting.

Fabricating an efficient electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) isthe most challenging task for overall water splitting. Herein, we utilized the confinement effect of molten sodium chloride (NaCl) to controllably prepare hollow Co/Co3O4 nanoparticles embedded into nitrogen-doped carbon (H-Co/Co3O4-NC). Experimental and theoretical investigations revealed that the interfacial interaction within Co/Co3O4 heterostructure played a pivotal role in modulating the electronic structure and facilitating the electron transfer. Meanwhile, the superiority of hollow nanostructure could promote the mesoscale mass diffusion. Remarkably, the as-prepared H-Co/Co3O4-NC catalyst achieved the low overpotentials of 316 mV and 252 mV towards OER and HER, respectively, which delivered overall water splitting with the potential of 1.76 V at a current density of 10 mA cm-2.