Quantification of Surface Reactive Oxygen Species at Co-Modified BiVO4 with Surface Interrogation Mode of Scanning Electrochemical Microscopy

Abstract

Our recent study suggests that cobalt modification can greatly improve the photoelectrochemical (PEC) water oxidation activities of n-BiVO4 (ACS Appl. Energy Mater., 1(5), 2283 (2018)). This enhancement is attributed to (1) the formation of a top layer of Co3O4 at BiVO4 surface as a cocatalyst and (2) the enrichment in electronic conductivity of BiVO4 upon Co doping. Here, surface interrogation mode of scanning electrochemical microscopy (SI-SECM) technique equipped with an ultramicroelectrode (UME) tip was employed to in-situ interrogate and quantify the surface adsorbed reactive oxygen species at Co-BiVO4 generated during PEC water oxidation. Experimental conditions of PEC water oxidation including applied potential and illumination time were found to play an important role in determining the surface coverage of the oxygen species. Their spontaneous decay under the open circuit condition was also characterized by increasing the time delay before interrogating the Co-BiVO4 surface.