In parallel with PV fabrication, a dendritic CuxIny electrocatalyst was synthesized following a template-assisted galvanostatic electrodeposition method. A reported procedure was adapted for catalyst deposition on 10 cm 2 Cu foils, whereas the alloy composition was adjusted to favour long-term CO2 reduction (see Methods, Supplementary Fig. ). Scanning electron microscopy (SEM) and high-angle annular dark field (HAADF) images revealed a hierarchical catalyst morphology, with nanoporous dendrites forming macropores with a 33 ± 3.3 µm pore size, whereas scanning transmission electron microscopy (STEM) elemental mapping confirmed the homogeneous distribution of Cu and In on the dendrite surface (Fig. , Supplementary Fig. ). Energy-dispersive X-ray (EDX) spectroscopy indicated an alloy composition of 92 wt% Cu and 8 wt% In (Cu92In8), whereas XRD confirmed the presence of CuIn alloy phases, along with some residual Cu and Cu2O phases. Accordingly, the 10 cm 2 catalyst preserved the morphology and elemental distribution of previously reported 0.84 cm 2 Cu96In4 samples. 54 A long-term controlled potential electrolysis (CPE) experiment was carried out at -0.4 V against the reversible hydrogen electrode (RHE) for 36 h, resembling the daytime operation of a PEC device during a 3-day test (Fig. ). The experiment was performed in a 3-electrode, one-compartment setup with a 10 cm 2 Cu92In8 catalyst, a Ag/AgCl reference and graphite foil counter electrode. A steady current density of -0.36 ± 0.03 mA cm -2 was sustained during CPE (Fig. ). A higher cathodic current was observed over the first ~3 min due to electrochemical reduction of the residual surface oxides (see inset of Fig. ). 164.4 µmol cm -2 CO and 80.9 µmol cm -2 H2 were obtained over the 36 h CPE test, amounting to faradaic yields (FYs) of 68.4 % and 33.7 % for CO and H2, respectively. A steady CO production was observed with time, whereas the H2 evolution rate increased after the first 15 h. This can be traced back to an in-situ reorganisation of the alloy phases, which is known to expose the Cu phase leading to higher H2 evolution activity at the applied electrochemical conditions. A cyclic voltammetry (CV) scan performed after long-term CPE indicated an early onset potential at around -0.3 V vs. RHE for aqueous CO2 reduction (Supplementary Fig. ), which suited our standalone artificial leaves for unassisted syngas (CO+H2) production.