The　integration　of　electrochemical　CO2　reduction　(CO2RR)　and　photoelectrochemical　water　oxidation　offers　a　sustainable　access　to　valuable　chemicals　and　fuels.　Here,　we　develop　a　rapidly　annealed　hematite　photoanode　with　a　photocurrent　density　of　2.83　mA　cm-2　at　1.7　VRHE　to　drive　the　full-reaction.　We　also　present　Cu-alloys　electrocatalysis　extended　from　CuInSnS4,　which　are　superior　in　both　activity　and　selec-tivity　for　CO2RR.　Specifically,　the　screened　CuInSn　achieves　a　CO2　to　HCOOH　Faradaic　efficiency　of　93%　at　a　cell　voltage　of-2.0　V　by　assembling　into　artificial　photosynthesis　cell.　The　stability　test　of　IT　exhibits　less　than　3%　degradation　over　24　h.　Furthermore,　in-situ　Raman　spectroscopy　reveals　that　both　CO2-3　and　CO2　are　involved　in　CO2RR　as　reactants.　The　preferential　affinity　of　C　for　H　in　the　*HCO2　intermediate　enables　an　improved　HCOOH-selectivity,　highlighting　the　role　of　multifunctional　Cu　in　reducing　the　cell　voltage　and　enhancing　the　photocurrent　density.(c)　2023　Science　Press　and　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences.　Published　by　ELSEVIER　B.V.　and　Science　Press.　All　rights　reserved.