Composition regulation of Ni-BDC MOF architecture to enhance electrocatalytic urea oxidation in alkaline solution

Abstract

Urea oxidation reaction (UOR) is a promising substitution of the oxygen evolution reaction (OER) on anode for highly efficient H2 production. However, the sluggish kinetics and high oxidation potential of NiII→NiIII severely limit the activity of Ni-based catalysts on electrochemical UOR. Herein, composition regulation is adopted for enhancing the electrocatalytic activity of nickel-benzene dicarboxylate framework (Ni-BDC MOF) derived electrode towards urea oxidation. In 1M KOH with 0.33M urea solution, the derived amorphous tri-metallic hydroxide layer on NiMnCo MOF surface, induced by electro-activation, exhibits the low onset potential and steeply rising current density with increasing applied potential. It receives a benchmark current density of 10 /100 mA·cm-2 at anode potential of 1.28 /1.33 V vs. RHE, respectively. In particular, a 500 mA·cm-2 current density reaches at impressively low potential of 1.41 V vs. RHE. The exceptional performance is ascribed to the fact that the open framework provides a large electrochemical active surface, and multi-components synergy decreases NiII →NiIII oxidation potential, enhances electron transfer and promotes UOR kinetics. This study suggests the rational composition regulation is a promising approach to improve the performance of Ni-based MOF materials towards electrocatalytic urea oxidation.