Semi-artificial leaf interfacing organic semiconductors and enzymes for solar chemical synthesis

Summary

Photoelectrochemical biohybrids combine the advantages of light-harvesting semiconductors and biocatalysts into a single compact device. However, limited device stability, the use of toxic elements, and non-innocent external components make a sustainable artificial photosynthetic reaction difficult to achieve. Here, we introduce organic photoelectrodes connected to an inverse opal TiO₂ matrix that hosts efficient hydrogenase or formate dehydrogenase, driving direct solar fuel synthesis. By co-immobilizing carbonic anhydrase, the organic bulk heterojunction photobiocathodes generate onset potentials of 1 V vs. RHE and photocurrent densities of up to −8 mA cm⁻² in a pH-neutral bicarbonate solution, attaining stable H₂ production or selective CO₂-to-formate conversion over 10 h. Sufficient aqueous formate was produced (∼2.5 mM) to serve as a hydride source for the asymmetric hydrogenation of acetophenone using a synthetic Noyori-Ikariya catalyst. The semi-artificial organic semiconductor—BiVO₄ tandem leaves achieve a solar-to-fuel efficiency of 0.6% and a Faradaic yield of 87% for formate.