Preparation of hollow nanorod CoxCu2−xSe/CF electrode assembled from nanoparticles and its urea-assisted hydrogen production performance

Urea-assisted water splitting is a promising method for the production of H2 with reduced energy consumption, which can also purify urea-rich wastewater. Nevertheless, the development of bifunctional electrocatalysts that exhibit exceptional efficiency and affordability for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) remains a challenging task. In this work, a MOFs-derived bifunctional electrode of Co-doped Cu2-xSe with a hollow nanorod structure assembled from nanoparticles is prepared on a copper foam substrate (CoxCu2-xSe/CF) by a three-step synthesis process. As anticipated, the CoxCu2-xSe/CF self-supported electrode shows promising performance in terms of the UOR and HER. This can be attributed to the unique hollow nanorod structure assembled from nanoparticles and incorporation of Co dopants, which can expose more active sites, enhance the electrochemical surface area, and facilitate faster reaction kinetics. When CoxCu2-xSe/CF was employed as the self-supported electrode for H2 production in a coupled HER||UOR system, only 1.51 V was required to drive a current density of 10 mA cm-2, which is 120 mV lower than the traditional water electrolysis system. and it also displays an outstanding stability, the current density retention ratio is approximately 82.1% after 70 h. Noteworthy, XRD, XPS and in-situ Raman analysis reveal that CoxCu2-xSe/CF can form highly active CuO and amorphous Cu(OH)2 as the active sites in UOR. This work proposes a strategy for H2 production and urea-containing wastewater treatment.