The production of hydrogen through electrolysis is considered as a feasible strategy to quench the world's clean-energy thirst. Compared with water electrolysis, urea electrolysis presents a more promising prospect in the way that it could carry out sewage treatment as well as energy-efficient hydrogen production at the same time. Herein, highly porous pomegranate-like Ni/C was synthesized from multivariate metal-organic frameworks and exhibits excellent hydrogen evolution activity with an unprecedented low overpotential of 40 mV at the current density of 10 mA cm-2 in 1 M KOH, ranking among the best earth-abundant electrocatalysts deposited on glassy carbon electrodes reported to date. In addition, it also displays superb anodic urea oxidation activity with an onset potential of 1.33 V vs RHE. Furthermore, a two-electrode urea electrolyzer with Ni/C as both the cathode and anode electrocatalyst was fabricated and generates 52 times more hydrogen than the water electrolyzer under the same conditions.
Keywords: electrocatalysis; hydrogen evolution reaction; metal−organic frameworks; urea oxidation reaction; water splitting.