Coupling platinum with the hierarchical NiCo/oxide heterostructures for highly efficient urea-assisted water electrolysis

Alloying the platinum with the nickel and cobalt is an efficient approach to lessen the usage of Pt without compromising the catalytic performance. Few studies have focused on coupling the Pt with the NiCo/oxide composite for hydrogen evolution reaction (HER). Herein, we synthesize three types of hierarchical Pt15-NiCo/oxide composites by impregnation, followed by calcination and hydrogenation treatment. The three electrocatalysts have similar intrinsic activity towards HER in 1.0 M KOH, while the Pt15-NiCo/CeO2−x displays the highest catalytic performance because of its large electrochemically active surface area, showing an extremely small overpotential of 12 mV at 100 mA cm−2, making it the best low-Pt-content electrocatalyst for HER. When used as a bifunctional electrocatalyst for urea-assisted hydrogen production, the Pt15-NiCo/CeO2−x demonstrates excellent catalytic performance with a very small cell voltage of 1.36 V to reach 10 mA cm−2 and robust long-term working stability. The outstanding catalytic performance of the Pt15-NiCo/CeO2−x is assigned to the unique-structure-induced abundant active sites, the optimized NiCo/CeO2−x, the suitable Pt loading, the synergy between the Pt and the NiCo, and the synergy between the PtNiCo and the CeO2−x. •Three types of hierarchical Pt-NiCo/oxide composites were prepared.•The three Pt15-NiCo/oxide composites presented similar intrinsic activity.•The number of active sites is the key factor determining the catalytic performance.•The Pt15-NiCo/Ce2−x has the largest electrochemically active surface area.•The Pt15-NiCo/CeO2−x has a small overpotential of 12 mV at 100 mA cm−2 for HER.