Vanadium<i>-</i>Doped Bimetallic Nanoporous Metal–Organic Frameworks as Bifunctional Electrocatalysts for Urea-Assisted Hydrogen Production

Abstract

Water electrolysis is considered a compelling path for generating ecofriendly and sustainable hydrogen fuel. To realize highly effective electrocatalytic water splitting, improving anodic oxygen evolution reaction (OER) activity is key because of its high overpotential. The urea oxidation reaction (UOR) is a promising method instead of the OER. Herein, a series of bimetallic nanoporous M 2 V-MOF materials (M = Fe, Co, and Ni) with vanadium doping is successfully synthesized by a one-step hydrothermal method and the materials are applied as electrocatalysts for water and urea electrolysis. Among the as-synthesized M 2 V-MOF materials, Fe 2 V-MOF as an impressive trifunctional electrocatalyst has very low overpotentials of 291 mV@10 mA cm –2 for the OER, 1.48 V@50 mA cm –2 for the UOR, and 182 mV@–10 mA cm –2 for the hydrogen evolution reaction (HER). Adapting it as a cathode and anode electrode for water splitting in 1.0 M KOH, a low cell voltage of 1.73 V is required for delivering 10 mA cm –2 . The urea-assisted electrolysis cell only needs 1.63 V to drive a current density of 10 mA cm –2 and exhibits excellent stability over 60 h.