Electrocatalytic water splitting by a low crystallinity CeOx@Co3O4 heterostructure

The development of bifunctional electrocatalysts with high activity and low cost is urgent but remains challenging for water splitting. Here, the core–shell heterostructure between ultrasmall ceria nanoparticles with low crystallinity and Co3O4 nanowires (CeOx@Co3O4) is successfully constructed via rapid electrodeposition. Systematic studies revealed that ultrasmall ceria with low crystallinity can induce the rich unsaturated active sites, accelerate the charge transfer and provide the strong electronic interaction between Co3O4 and ceria. As a result, a strong enhancement of electrocatalytic activity at the CeOx@Co3O4 heterostructure is reported with low overpotential (252 and 106 mV at 10 mA cm−2) and small Tafel slopes (41 and 106 mV dec−1) for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. The electrolyzer based on CeOx@Co3O4 heterostructure shows a low cell voltage of 1.57 V and excellent stability to attain a current density of 10 mA cm−2. This work provides a valuable reference for the preparation of bifunctional electrocatalysts with low cost and high activity.