Red-Light-Driven Biophotochemical Diode Based on a Microorganism-Silicon Nanowire Interface for Stable and Efficient Bias-Free CO2 Reduction

Abstract

Artificial photosynthesis offers a promising route for sustainable liquid fuel and feedstock production, yet integrating efficient CO2 reduction catalysts with light-harvesting systems remains challenging. Here, we present a biophotochemical diode that couples microorganism-driven CO2 reduction with glycerol oxidation, enabled by silicon nanowire photoelectrodes under varying red-light intensities. Tuning the biotic-abiotic interface-by increasing biocatalyst loading and adjusting the catholyte pH to mitigate local alkalization-significantly improves performance and stability. The enhanced-loading biocathode maintains a high faradaic efficiency across a wide potential range, even under elevated light intensities. At 60 mW/cm(2), the system achieves a bias-free current density of 3.5 mA/cm(2). Long-term stability testing at 40 mW/cm(2) demonstrates stable operation for over 100 h. The photoanode generates valuable C-3 products, primarily glycerate and lactate, enhancing the economic viability. This work showcases the importance of microenvironmental control at the biotic-abiotic interface and establishes a scalable platform for light-driven CO2 reduction using earth-abundant silicon.