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| Journal Article | FZJ-2026-03147 |
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2026
Royal Society of Chemistry
Cambridge
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Please use a persistent id in citations: doi:10.1039/D6SE00442C
Abstract: Solar-driven CO2 reduction to liquid fuels such as formate provides an attractive solution for renewable energy storage. This paper investigates the application of an electrochemical (EC) cell for CO2 reduction directly coupled to a photovoltaic (PV) module, which enables early-stage, long-term storage of solar energy through a waste-to-value pathway. An earth-abundant gas-diffusion cathode based on sulfur-modified copper oxide is employed as the core catalyst for the CO2 reduction process. The cathode is synthesized and tested in a gas-diffusion electrode (GDE) flow-cell configuration under conditions of a realistic, directly coupled PV-EC device. Realistic field operation of the PV-EC device is reproduced using a hardware PV emulator replicating the Si PV module I-V characteristics over a full day–night irradiance and temperature time series, while EC cell operates at 40 °C. Under these realistic operating conditions, the directly coupled PV-EC device demonstrates self-sustained operation with a high energy-coupling efficiency of 94%. The sulfur-modified copper oxide catalyst achieves stable CO2 reduction with a total solar-to-chemical efficiency of ~12% and a solar-to-formate efficiency (STCHCOO-) of ~8% at current densities of 6 - 19 mA cm-2. Our achieved STCHCOO- is presented alongside recorded operating current densities (jOP) against previously reported literature, allowing for direct comparison between different electrochemical catalysts, cell designs or coupling strategies. Our results demonstrate the feasibility of liquid-fuel production under realistic PV-driven direct-coupling operation, representing a key step toward early-stage long-term storage of surplus PV output in renewable-energy-dominated systems, and coupling of PV generation to non-electrified energy sectors.
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