Pd/CeO<sub>2</sub> Interface with Abundant Oxygen\nVacancies for Alkaline Hydrogen Evolution/Oxidation Reaction

Hydrogen\nevolution reaction and hydrogen oxidation reaction (HER/HOR)\nare two key reactions in the electrolysis of water to produce green\nhydrogen and fuel cells, respectively. However, the slow kinetics\nof HER/HOR under alkaline conditions and lack of catalysts with good\nactivity and durability limit their development and application. Here,\nPd nanoparticles supported by CeO<sub>2</sub>/C with abundant oxygen\nvacancies were synthesized for alkaline HER/HOR. The results of physical\ncharacterizations and electrochemical measurements indicated that\nsmall-size Pd nanoparticles were in full contact with CeO<sub>2</sub>, and charge transfer occurred at the Pd–CeO<sub>2</sub> interface.\nThe rich Pd–CeO<sub>2</sub> interface and the interaction between\nmetal and metal oxide carriers greatly improved the electrocatalytic\nactivity of HER and HOR under alkaline conditions. The optimal Pd/CeO<sub>2</sub>/C exhibited excellent HER/HOR activity with a higher HER\nexchange current density (1.963 mA cm<sup>–2</sup>) than commercial\nPt/C. Furthermore, the HER and HOR mass activity of Pd/CeO<sub>2</sub>/C reached 33 times and 9.2 times that of Pd/C, respectively. Pd/CeO<sub>2</sub>/C exhibited enhanced electrocatalytic stability due to the\nanchoring of Pd via abundant oxygen vacancy defects in CeO<sub>2</sub>/C. This work provides a meaningful reference for the rational regulation\nof metal–support interfaces and the application of metal-oxide–support-based\nelectrocatalysts in electrocatalytic reactions.