Benchmark photocurrents of -5 mA cm -2 were also observed for OPV|IO-TiO2|FDH+CA photocathodes at 0 V vs. RHE, showing improved photocurrent generation and charge extraction over state-of-the-art devices 7,10,14 (Fig. , see Table for literature comparison). While bare OPV|IO-TiO2 photocathodes displayed a transient photocurrent spike upon illumination, this was notably absent in OPV|IO-TiO2|FDH+CA photoelectrodes (Fig. ). The photocathodes also maintained reproducible CO2 reduction over 10 h CPE at 0.6 V vs. RHE, producing 156±8 µmolformate cm -2 with a FY of 98±2% (Fig. , Fig. and Table ). Degradation of FDH and the buried PV device contributed to a gradual decrease in performance, supported by declining onset potentials and photocurrent densities after 10 h (Fig. ) . 1 H NMR spectra of the C-labelled product mixture further confirmed that C-formate was solely derived from CO2 reduction (Fig. and Fig. ).