Metal-Free Semiconductor-Based Bio-Nano Hybrids for Sustainable CO2-to-CH4 Conversion with High Quantum Yield

Bio-nano hybrids with methanogens and nano-semiconductors provide an innovative strategy for solar-driven CO2-to-CH4 conversion; however, the efficiency mismatch between electron production and utilisation results in low quantum yield and CH4 selectivity. Herein, we report the integration of metal-free polymeric carbon nitrides (CNx) decorated with cyanamide (NCN) groups and Methanosarcina barkeri (M. b). The self-assembled M. b-(CNx)-C-NCN exhibited a quantum yield of 50.3 % with 92.3 % CH4 selectivity under illumination, which outperforms other reported bio-nano hybrid systems and photocatalytic systems for CO2 reduction. This excellent performance was attributed to the distinct capacitance and conductive effects of (CNx)-C-NCN, which promoted electron storage and redistribution at the biotic-abiotic interface to alleviate recombination losses and side reaction. This study provides new design guidelines for bio-nano hybrids for the sustainable photocatalytic reduction of CO2 into fuels.