Integrated Silver-Decorated Setaria Viridis Microfiber Carbon Electrode for Efficient Electrochemical CO2 Reduction

Biomass-derived carbons are promising supports for electrochemical CO 2 reduction (ECO 2 R) due to their natural abundance and renewability. However, achieving high selectivity and industrially relevant current densities with biomass-derived carbon catalysts remains challenging. Here, inspired by the porous microchannel and bristle-like structure of Setaria viridis (SV), a one-pot co-pyrolysis strategy was employed to synthesize hierarchically porous silver-decorated nitrogen-doped carbon catalysts. The SV-derived carbon, combined with optimized nitrogen doping and silver decoration (Ag/N-SV1), yields a hierarchically porous carbon catalyst with tuned electronic states that enhance CO 2 adsorption and stabilize the ⁎ COOH intermediate, thereby improving CO selectivity. In an H-cell, Ag/N-SV1 achieved a CO Faradaic efficiency (FE CO ) of 89% with a partial current density (j CO ) of -6.7   mA   cm -2 at -0.98   V vs. RHE, while maintaining stable operation for 20   hours. In contrast, nitrogen-doped SV (N-SV1) primarily produced formate, highlighting the critical role of Ag in CO selectivity. Furthermore, the hydrophobically treated Ag/N-SV1 gas diffusion electrode (GDE) achieved a j CO of -123 mA cm -2 in the flow cell, demonstrating scalability and practical promise. Density functional theory (DFT) calculations revealed that Ag-N coordination lowers the energy barrier for ⁎ COOH formation, resulting in enhanced CO selectivity. This study highlights Setaria viridis as a renewable and sustainable biomass precursor, validating the co-pyrolysis approach as an effective strategy for designing cost-effective Ag-N materials for sustainable electrochemical applications.