Spontaneous Solar Syngas Production Driven by Energetically Favorable Wastewater Microbial Anodes

Abstract

The photoelectrochemical (PEC) CO2 reduction to syngas is an attractive strategy for solar to fuel conversion, however, the high overpotential, inadequate selectivity, and high cost call for alternative solutions. Here we demonstrate a hybrid microbial photoelectrochemical (MPEC) system which contains a microbial anode capable of oxidizing free waste organics in wastewater and reducing the oxidation potential by 1.1 V, compared to abiotic water oxidation on PEC anode. Moreover, the MPEC employs a power management circuit (PMC) to enable several low-energy producing reactions operated in the same solution medium to conquer high-overpotential reactions. The nanowire silicon photocathode integrated with a selective single-atom Nickel catalyst (Si NW/Ni SA) achieved up to ~80% Faradaic efficiency for CO generation with a highly tunable CO:H2 generation ratio (0.1 to 6.8). When the bioanode couple with the Si NW/Ni SA, up to 1.1 mA cm−2 spontaneous photocurrent density can be accomplished for syngas generation.