Revealing charge migration in a Multi-Multi photocatalyst by in situ irradiated X-ray photoelectron spectroscopy

•The triple-modified WS2/ CNFs/ZnIn2S4 system was first constructed.•The significant increase in photocatalytic efficiency of ZnIn2S4 was achieved.•Charge enrichment caused by defects was revealed by DFT calculations and ISI-XPS.•The accurate charge transfer pathway was directly shown by ISI-XPS.•ISI-XPS, as a universal method for studying mechanisms, were fully discussed.