Wei Zhao’s scientific contributions

We report here an in situ method to monitor and optimize formation of thin semiconductor passive films of bismuth oxides and sulfides for enhanced photoelectrochemical performances. It was conducted by cyclic voltammetry under visible light illumination in a mixed solution of Na2SO3 and Na2S. Electrooxidation and sulfurization of Bi electrodes occurred simultaneously during the potential cyclings between -1 V and 0 V (vs. Hg vertical bar Hg2SO4(s)vertical bar K2SO4 (saturated)), and the semiconductor passive film with an appropriate thickness was formed effectively under light illumination. In comparison with the composite film of Bi2S3/Bi2O3 loaded on conductive glass, enhanced photoelectrochemical performances were observed in much wider potential ranges on the prepared semiconductor passive film due to its very compact coverage. Higher anodic photocurrent density was obtained from -1 V to 10 V on the semiconductor passive film prepared under light illumination than in dark, and under galvanostatic operation the anodic potential went back and forth between -1.1 V and 9.8 V rapidly while the visible light illumination was on and off. We expect that these photoelectrochemical characteristics will find applications in photoelectrochemical hydrogen production, photodetectors and photoswitches. (C) 2015 The Electrochemical Society.

Direct electrochemical shaping of metal surfaces into micro/nano-structures with desired functions is interesting and attractive. In this work, we employed square wave potential pulses (SWPP) to shape a smooth Cu surface into micro/nano-structures efficiently in a blank H2SO4 solution. Delightedly, we obtained Cu sub-micrometric islands on the surface with very strong surface enhanced Raman scattering (SERS) effect in 5 s, and fabricated a coral-like micro/nano-structured copper film with superhydrophobicity in 40 s. This method is green, facile, fast, and easy to control.

Electrochemical fabrication of micro/nanostructured metallic surfaces with superhydrophobicity has recently aroused great attention. However, the origin still remains unclear why smooth hydrophilic metal surfaces become superhydrophobic by making micro/nanostructures without additional surface modifications. In this work, several superhydrophobic micro/nanostructured metal surfaces were prepared by a facile one-step electrodeposition process, including non-noble and noble metals such as copper, nickel, cadmium, zinc, gold, and palladium with (e.g. Cu) or without (e.g. Au) surface oxide films. We demonstrated by SEM and XPS that both hierarchical micro/nanostructures and spontaneous adsorption of airborne hydrocarbons endowed these surfaces with excellent superhydrophobicity. We revealed by XPS that the adsorption of airborne hydrocarbons at the Ar+-etched clean Au surface was rather quick, such that organic contamination can hardly be prevented in practical operation of surface wetting investigation. We also confirmed by XPS that ultraviolet-O3 treatment of the superhydrophobic metal surfaces did not remove the adsorbed hydrocarbons completely, but mainly oxidized them into hydrophilic oxygen-containing organic substances. We hope our findings here shed new light on deeper understanding of superhydrophobicity for micro/nanostructured metal surfaces with and without surface oxide films.