• Rational regulation of coordination environments on both photoanode and cathode enhances overall solar-driven CO2 conversion.
• Defect-engineered FeNi catalysts on BiVO4 achieve a high OER photocurrent of 6.51 mA cm−2 at 1.23 VRHE.
• Single-atom Co-N5 sites on N-rich carbon boost CO2-to-CO selectivity with faradaic efficiency >90%.
• Integrated system reaches record CO production rate of 109.4 μmol cm−2 h−1 and solar conversion efficiency of 5.41%.