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.

光催化可以有效降解废水中新兴的（微）污染物并实现先进的水处理目标，其中太阳能转换效率低仍然是一个挑战。一个关键的决定因素是微污染物的有效吸附，这一点很难定义，特别是对于在不同长度尺度和（非）反应条件下具有表面异质性的光催化剂。在这里，我们报告了一种可推广的成像技术 adCOMPEITS（基于吸附的超分辨率竞争成像技术），并在非催化和光催化下以纳米分辨率量化非荧光微污染物在异质结构 Au/TiO ₂光催化剂上的吸附行为（电）催化条件。我们发现TiO ₂上微污染物吸附的长程增强，达到微米长度尺度，这源于TiO ₂在接触金属助催化剂时的长程表面能带弯曲。我们进一步设计能带弯曲，以有效调节对分子吸附的长程影响。这里的成像技术和科学发现应该为理解和设计金属促进的光催化剂的许多应用开辟道路。