Metal–Organic Framework Nanosheet Electrocatalysts for Efficient H₂ Production from Methanol Solution: Methanol-Assisted Water Splitting or Methanol Reforming?

Abstract

Hydrogen (H₂) is presently one of the most promising clean and renewable energy sources, but the conventional hydrogen production by electrochemical water-splitting, though of great potential and extensively studied, is seriously obstructed especially by the anodic oxygen evolution reaction because of its sluggish kinetics. Herein, we report the efficient hydrogen production from methanol solution using facile-synthesized ultrathin 2D bi-metal-organic framework nanosheets (UMOFNs) as a precious metal-free anodic catalyst. The prepared UMOFNs showed a much lowered anodic potential of 1.365 (V vs reversible hydrogen electrode) at 10 mA cm^-2, which was markedly 232 mV lower than that in conventional water splitting, and moreover, the average turnover frequency reached 19.62 s^-1. Benefiting from nearly 100% Faraday efficiency of H₂ production on the counter graphite carbon electrodes without additional electrocatalysts, high-purity hydrogen was produced with enhanced efficiency. More importantly, the anodic electro-reaction mechanism has been evidenced experimentally: the electrocatalytic hydrogen production from the methanol solution is a methanol-assisted water splitting, rather than a methanol-reforming process as claimed in a number of literature studies, in which methanol is oxidized as a sacrificing agent in place of water oxidization in pure water.