Electrocatalytic Water Oxidation Promoted by 3 D Nanoarchitectured Turbostratic δ-MnOx on Carbon Nanotubes.

The development of manganese-based water oxidation electrocatalysts is desirable for the production of solar fuels, as manganese is earth-abundant, inexpensive, non-toxic, and has been employed by the Photosystem II in nature for a billion years. Herein, we directly constructed a 3 D nanoarchitectured turbostratic δ-MnOx on carbon nanotube-modified nickel foam (MnOx /CNT/NF) by electrodeposition and a subsequent annealing process. The MnOx /CNT/NF electrode gives a benchmark catalytic current density (10 mA cm-2 ) at an overpotential (η) of 270 mV under alkaline conditions. A steady current density of 19 mA cm-2 is obtained during electrolysis at 1.53 V for 1.0 h. To the best of our knowledge, this work represents the most efficient manganese-oxide-based water oxidation electrode and demonstrates that manganese oxides, as a structural and functional model of oxygen-evolving complex (OEC) in Photosystem II, can also become comparable to those of most Ni- and Co-based catalysts.