Efficient H2 production in a microbial photoelectrochemical cell with a composite Cu2O/NiOx photocathode under visible light

Microbial photoelectrochemical cells (MPEC) is a state-of-the-art and self-sustained 'waste-to-energy' solution through coupling a synergistic microbial conversion of waste organics into electron and proton in a bioanode and photoelectrochemical catalysis of proton reduction for hydrogen evolution in a photocathode. With the advantage of visible light adsorption, p-type semiconductor Cu2O has exhibited superior photocatalytic potential for hydrogen evolution reaction (HER), but the instability of p-type Cu2O hinders its further practical application. Here, we fabricated a Cu2O/NiOx composite photocathode by spin coating a thin film of NiOx on Cu2O photocathode to improve its stability and photocurrent. Results showed that NiOx layer on Cu2O had a trade-off effect on photocathode performance. The thicker of NiOx film on Cu2O, the lower of the photocurrent, but more stable of the Cu2O electrode. With an optimal 240 nm thickness of NiOx layer, the Cu2O/NiOx composite photocathode extracted excited electrons effectively, and a H2 production rate of 5.09 μL h−1 cm−2 was obtained from a MPEC under continuous light illumination with 0.2 V external bias. By tuning the synergistic effect of bioanode and photocathode, MPEC could provide a feasible solution on simultaneously organic conversion and energy restoration from wastewater and solar light.