Nickel diselenide nanoflakes give superior urea electrocatalytic conversion

Urea electro-oxidation reaction (UOR) is a promising but challenging renewable energy production technology, which generally requires lower electrochemical potential, and shows the capabilities in eliminating a potentially harmful substance from wastewater and/or converting human waste into treasure. However, the state-of-the art UOR suffers from the sluggish kinetics because of the 6 e(-) transfer process involvement. Herein, as a proof-of-concept study, we synthesized the Ni-III -rich nickel diselenide nanoflake through a facile hydrothermal reaction. Compared to the counterpart nickel (oxy) hydroxide, the selenylation processing of nickel successfully produces synergetic effects of more exposed active sites and effective electron transports. Particularly, due to the Ni-III -rich nature of the as-synthesized nickel diselenide, the reduction/oxidation reactions between Ni-II and Ni-III is greatly accelerated, which in turn effectively decreases the required overpotentials, prolongate the catalytic lifetime, giving rise to the significantly enhanced UOR performances. In-depth mechanistic analysis evidences that the restructure of nickel diselenide (vs. nickel oxide hydroxide) could be the main reason for affording the decent UOR activity as the oxidation from Ni-II to Ni-III was simultaneous occurred during the selenide species disappear process, a result that may be extended to other selenide-based systems. (C) 2018 Elsevier Ltd. All rights reserved.