Molecular Photoelectrocatalysts for Visible Light-Driven Hydrogen Evolution from Neutral Water

Abstract

A light-activated hydrogen evolution electrocatalyst is reported. Hydrogen evolves near the thermodynamic potential when aqueous solutions of the iridium chloride complex [Cp*Ir­(bpy)­(Cl)]­[Cl] (<b>1</b>, bpy = 2,2′-bipyridine) are illuminated by visible light. In the dark, no electrocatalytic activity is observed. This unique hydrogen evolution mechanism is made possible because a single transition metal complex is the active light absorber and active electrocatalyst. Optimization by tuning the electronic structure of the catalyst and varying reaction conditions resulted in H₂ evolution with faster rates, even at milder applied potentials (<i>k</i>_obs ∼ 0.1 s^–1 at 100 mV electrochemical overpotential)