A bioinspired water oxidation catalyst that is ∼1/10th as active as the photosystem II oxygen evolving center at pH 7: a study of activity and stability factors

Abstract

The activity and stability of a heterogeneous water oxidation catalyst inspired by the Photosystem II – Oxygen Evolving Center (PSII-OEC) is reported. Ca-doped birnessite MnO_x supported on a liquid crystalline reduced graphene oxide (LCrGO) substrate exhibited unprecedented performance for an abiological catalyst at pH 7, including an exceedingly low onset overpotential of 0.52 V (vs. 0.48 V reported for the PSII-OEC, 0.75 V for Pt, and 0.72 V for birnesite MnO_x) and remarkably high activity per unit area at 0.56 V overpotential (∼10% that of a hypothetical, closely-packed monolayer of OEC sites at their optimum density of 10¹⁴ sites per cm²).