Amorphous iron-doped nickel boride with facilitated structural reconstruction and dual active sites for efficient urea electrooxidation

Abstract

Designing transition metal-based catalysts for efficient urea oxidation reaction (UOR) is important for realizing energy-saving hydrogen production via urea-rich (waste)water electrolysis. Herein, we have developed an iron-doped amorphous nickel boride electrocatalyst (aFe-NiB) for UOR. Compared with the undoped and crystalline counterparts, aFe-NiB exhibits a higher activity and the benchmark current density of 10 mA cm−2 can be attained at 1.298 V vs. reversible hydrogen electrode (RHE). Coupled with an efficient hydrogen evolution catalyst, the aFe-NiB-assisted urine electrolyzer can attain a 46 times higher H2 production rate than the water electrolyzer at 1.50 V. Further study reveals a crystallinity-dependent structure self-reconstruction process during UOR. aFe-NiB attains complete phase evolution from boride to electroactive Fe-doped NiOOH. In addition, density functional theory calculations imply that Fe dopants can improve intrinsic catalytic activity via electronic structure regulation of the self-evolved NiOOH and forming heterogeneous bimetallic active sites for UOR. This study provides meaningful insights into the crystallinity-dependent UOR performance and effective strategies to develop efficient UOR (pre)catalysts with dual active sites. Significantly, the demonstrated direct wastewater (urine) electrolysis paves the way for net zero buildings -targeted human waste reutilization.