Top-Open Hollow Nanocubes of Ni-Doped Cu Oxides on Ni Foam: Scalable Oxygen Evolution Electrode via Galvanic Displacement and Face-Selective Etching.

Abstract

Self-standing and cost-effective electrodes for high-performance oxygen evolution reaction (OER) are vital for emerging energy storage and conversion technologies. We report a scalable binder-free OER electrode with open hollow nanocubes of Ni-doped CuOx on Ni foam (hNC/NF) through spontaneous galvanic displacement followed by simple electrochemical oxidation. Face-selective etching for the unique structure of hollow nanocubes with large open ends is achieved by utilizing the different accessibility of the top and side faces of cubes to solution species, more specifically the depletion of reactants between the densely supported nanocubes. Besides, the in situ deposition on Ni foam allows spontaneous Ni doping, which, as revealed by DFT calculations, fortunately strengthens the adsorption of oxygenated intermediates and therefore could optimize the free energy path of OER on Cu oxides. Benefiting further from the high accessible surface area of the unique open hollow architecture, the hNC/NF exhibits an outstanding OER activity with a small overpotential (η = 305 mV at 10 mA cm-2) as well as excellent stability without significant decay after 120 h operation. To our knowledge, this should represent the best OER performance of Cu-based electrocatalysts and is competitive with those based on Fe-group metals. Besides, the hNC/NF-based water electrolyzer delivers a performance of 1.50 V cell voltage at 10 mA cm-2, offering great promise for practical application.