Sustained Biotic-Abiotic Hybrids Methanogenesis Enabled Using Metal-Free Black Phosphorus/Carbon Nitride

Biotic-abiotic hybrid systems (BAHs) constructed by integrating biological methanogens with photocatalysts offer novel approaches for the effective solar-driven conversion of CO₂ to CH₄, providing significant inspiration for achieving carbon neutrality and alleviating the energy crisis. As metal photocatalysts would cause photocorrosion that damages microbial cells and lead to system imbalance. Therefore, exploring suitable metal-free photocatalysts is of particular importance in the search for more efficient and sustainable BAHs to improve the actual operability and applicability. Herein, black phosphorus/carbon nitride (BPCN ) as an alternative metal-free heterostructure was combined with Methanosarcina barkeri (M. barkeri) to construct M. barkeri-BPCN hybrid systems, and their cyclic methanogenesis performance was investigated. Our results demonstrated that BPCN promotes the separation of photogenerated charges and enhances the quantum yield, providing a sustained energy source for the cyclically driven M. barkeri reduction of CO₂ to CH₄ under visible light. Our system achieved a total CH₄ yield of 1087.45 ± 29.14 μmol g_cat ^-1 after three cycles, 1.96 times higher than that of M. barkeri-Ni@CdS. M. barkeri-BPCN overcame the defects of the metal photocatalyst and kept cell permeability, achieving cyclic stability and effectively maintaining the activity of M. barkeri. These results highlight the viable role of BPCN as a metal-free photocatalysts in the construction of BAHs for the sustained and efficient methanation of CO₂, which is conducive to the development of an environmentally-friendly, low-cost, and efficient strategy for the conversion of CO₂ to CH₄.