Surface chemo-mechanics coupling of MnO2/Au layered composites under electrochemical environment

Abstract

The intersection of surface mechanics and electrochemistry has gradually become a prominent topic in the realm of new energy research. To explore the influence of the electrochemical process on the stress of energy storage electrode composite, supercapacitor material manganese dioxide (MnO2) was selected as the coating and the MnO2/Au composites were prepared by the electrochemical deposition. The surface stress of MnO2/Au composites under different electrochemical modes and the stress variation law of MnO2 with varying thicknesses were determined. The addition of MnO2 could alter the stress response and the strain magnitude of the gold electrode with varied electrochemical potential. The reversible tensile strain within the Au surface during 0.3 ∼ 0.8 V charging was induced by the absorption of SO42−, while the compressive strain of the MnO2/Au composites was related to the extraction of Na+ ions resulting from the redox pseudocapacitance of MnO2. Notably, the produced stress exhibited a linear correlation with the capacitance. And the long-cycle tests revealed that as the specific capacitance of electrodes decreased, the induced tensile stress progressively diminished. This study emphasized the surface chemo-mechanics coupling of both the Au layer and MnO2/Au composites, which would provide a new approach to regulating surface strain in the solid–liquid interface.