Increasing oxygen vacancies in CeO2 nanocrystals by Ni doping and reduced graphene oxide decoration towards electrocatalytic hydrogen evolution

Oxygen vacancy (V-O) engineering has proved to be an effective approach for improving the hydrogen evolution reaction (HER) performance of low-cost metal oxide electrocatalysts. Cerium dioxide (CeO2), an abundant rare-earth metal oxide, is famous for its easy formation of V-O and high oxygen mobility, which is believed to be conducive to its application in electrocatalytic HER. Herein, this study reports a facile modification strategy using rGO as a conductive support for CeO2 nanocrystals and introducing the transition metal Ni as the active dopant, resulting in the construction of the Ni-rGO/CeO2 electrocatalyst. It is found that rGO decoration prevents the aggregation of CeO2 NCs and increases the V-O concentration in the CeO2 nanocrystals as well, while the introduced Ni leads to further formation of V-O and serves as the active site for the HER reaction. Thus, the Ni-rGO/CeO2 electrocatalyst shows relatively low overpotential, a low Tafel slope, and great stability for HER, which is attributed to the synergistic effect of rGO decoration and Ni doping. This kind of facile strategy is promising for the design of noble-metal-free and low-cost electrocatalysts by the functional modification of CeO2-based nanocatalysts.