What Is the Mechanism by which the Introduction of Amorphous SeO_x Effectively Promotes Urea-Assisted Water...

Nickel hydroxide (Ni(OH)₂) is considered to be one of the most promising electrocatalysts for urea oxidation reaction (UOR) under alkaline conditions due to its flexible structure, wide composition and abundant 3D electrons. However, its slow electrochemical reaction rate, high affinity for the reaction intermediate *COOH, easy exposure to low exponential crystal faces and limited metal active sites that seriously hinder the further improvement of UOR activities. Herein it is reported electrocatalyst composed of rich oxygen-vacancy (O_v) defects with amorphous SeO_x-covered Ni(OH)₂ (O_v-SeO_x/Ni(OH)₂). Surprisingly, at 100 mA cm^-2, compared with Ni(OH)₂ (1.46 V (vs RHE)), O_v-SeO_x/Ni(OH)₂ has a potential of 1.35 V. Meanwhile, O_v-SeO_x/Ni(OH)₂ catalyst also showed good hydrogen evolution reaction (HER) performance, so it is used as the electrolytic cell assembled by UOR and HER bifunctional catalysts and only 1.57 V could reach 100 mA cm^-2. Density functional theory (DFT) study revealed that introduce of amorphous SeO_x optimizes the electronic structure of the central active metal, amorphous/crystalline interfaces promote charge-carrier transfer, shift d-band center and entail numerous spin-polarized electrons during the reaction, which speeds up the UOR reaction kinetics.