In situ scanning tunneling microscopy investigation of restructuring and anodic dissolution of Cu(111) electrode in sulphuric acid solution

In situ scanning tunneling microscopy (STM) has been employed to study the structures, dissolution/redeposition and anodic dissolution of Cu(111) surface in aqueous sulphuric acid on an atomic scale. A short-range periodicity resulting from the ordered (bi)sulphate adlayer and a long-range periodicity (Moiré pattern) have been observed, which is consistent with previous work. The Moiré pattern lying within ±11° to the close-packed {110} directions of the unreconstructed Cu(111) surface has been further determined here. We focus here on the anodic dissolution and restructuring of the surface in the presence of adsorbed (bi)sulphate. We are able to image the Moiré pattern of the (bi)sulphate covered surface during such dynamic processes and hence determine preferential etching and redeposition directions. It was found that step edges running along the Moiré pattern are most stable during such dynamic processes. The Moiré depressions are typically located at a fixed distance from the step edge. The Moiré pattern does not run along the close-packed directions of the (bi)sulphate adlayer so the step reorientation on (bi)sulphate covered Cu(111) is significantly different from the behaviour on the chloride covered surface, for which it has been reported previously that the steps orientated along close-packed Cl rows are stabilised. A different mechanism is suggested for the dissolution and redeposition kinetics on (bi)sulphate covered surfaces, in which the Moiré pattern ‘steers’ the dissolution or growth directions. A spiral growth during Cu local redeposition originating from dislocations has also been observed and discussed.