Long-range enhancements of micropollutant adsorption on metal-promoted photocatalysts

Photocatalysis can effectively degrade emerging (micro)pollutants in wastewater and achieve advanced water treatment objectives, wherein the low solar energy conversion efficiency remains a challenge. One key determinant is the effective adsorption of micropollutants, which is challenging to define, especially for photocatalysts with surface heterogeneity over different length scales and under (non-)reactive conditions. Here we report a generalizable imaging technique adCOMPEITS (adsorption-based competition-enabled imaging technique with super-resolution) and quantify the adsorption behaviours of non-fluorescent micropollutants on heterostructured Au/TiO2 photocatalysts at nanometre resolution under both non-catalytic and photo(electro)catalytic conditions. We discover a long-range enhancement of micropollutant adsorption on TiO2, which reaches micrometre-length scale and stems from the long-range surface band bending of TiO2 upon contacting metal co-catalyst. We further engineer the band bending to effectively modulate the long-range effects on molecular adsorption. The imaging technique and the scientific discoveries here should open avenues towards understanding and engineering metal-promoted photocatalysts for many applications. Methods for studying the adsorption behaviour of molecules onto surfaces under reactive and non-reactive conditions are needed to improve photocatalysts for water treatment. Here the authors develop an imaging technique, adCOMPEITS, to quantify the adsorption of micropollutants on Au/TiO2 and identify a long-range enhancement effect.