Unveiling the role of bisulfide in the photocatalytic splitting of H2S in aqueous solutions

•HS–ion was the main actor in hydrogen generation mechanism.•Competitive adsorption above a critical HS–concentration inhibited H2 production.•H+ ion did not play a significant role towards hydrogen generation.•H2 production over brookite-rutile sol–gel catalyst doubled that of commercial benchmark.•Brookite-rutile catalysts showed excellent reusability.