Unassisted photoelectrochemical CO₂-to-liquid fuel splitting over 12% solar conversion efficiency

The increasing need to control anthropogenic CO₂ emissions and conversion to fuels features the necessity for innovative solutions, one of which is photoelectrochemical system. This approach, capable of yielding gaseous production progressively, is facing challenges for liquid fuels generation due to optical, electrical, and catalytic properties. This study employs a standalone photoelectrochemical setup, in which InGaP/GaAs/Ge photoanode is integrated with tin-modified bismuth oxide cathode to convert CO₂ into liquid formic acid. In unassisted two-electrode assembly, setup exemplifies its operational durability for 100 h, during which it maintains an average Faradaic efficiency of 88% with 17.3 mmol L^-1 h^-1 of yield, thereby excelling in average solar-to-fuel conversion efficiency at 12% with 60% of electrical energy efficiency under one sun illumination. This significant performance is further associated with metal-semiconductor interface formation between tin and bismuth oxide, which bridges electronic structures and generates an electric field at their interfaces. This study outperforms conventional solar-driven systems in operational durability and liquid fuel production.