The　electron　transfer　in　photocatalytic　reaction,　including　electron　transfer　between　the　components　in　the　catalyst,　electron　transfer　between　reactant　molecules　and　catalysts.　Fe2+/Fe3+　and　oxygen　vacancies　(VOs)　were　simultaneously　introduced　in　Fe-In2O3,　the　5　wt%　Fe-In2O3　exhibited　a　13.7-fold　increase　in　activity　(4.80　mmol·g−1·h−1)　compared　to　the　In2O3　and　a　CO　selectivity　of　approximately　84.32　%.　Multiple　in-situ　techniques　indicated　that　the　doping　of　FeOX　serves　to　effectively　modulate　the　concentration　of　VOs,　FeOX　and　In2O3　form　a　p-n　heterojunction　interfacial　structure　and　match　energy　bands,　promoting　carrier　separation.　More　importantly,　Fe2+,　In2+,　and　VOs　serve　as　electron-donating　adsorption　sites,　increasing　the　number　of　electrons　received　by　CO2　and　H2O,　which　causing　pre-reduction　activation　of　the　reactant　molecules.　Eventually　the　dual-reduction　reaction　of　CO2　and　H2O　were　realized,　subsequently,　CO2　was　selectively　converted　into　CO　through　intermediate　species　such　as　formate.　This　study　employs　Fe2+　and　VOs　to　synergistic　optimize　the　progressive　transfer　of　photogenerated　electrons,　and　presents　a　novel　approach　for　elucidating　the　catalytic　mechanism.　©　2024　Elsevier　B.V.