Effects of Three Different Biochars on Microbial Community and Their Corresponding Bioelectricity Generation Mechanism in PMFCs Under Unsaturated Conditions

This study investigates the effects of three biochars—corn straw biochar (CSB), reed straw biochar (RSB), and applewood biochar (AWB)—on microbial communities and bioelectricity generation in plant microbial fuel cells (PMFCs) under unsaturated soil conditions. Biochars were incorporated at 5% mass ratio into silty lean clay soil planted with Hydrocotyle vulgaris , with bioelectricity, soil moisture, and microbial diversity monitored during drought simulation. Key results revealed that RSB‐amended PMFCs achieved the highest power density (1608 mW/m 2 ), surpassing AWB (730 mW/m 2 ), CSB (63 mW/m 2 ), and the control (52 mW/m 2 ). RSB enhanced bioelectric potential and current by 4.5× and 23 × , respectively, compared to the control, attributed to its high porosity (29.198 m 2 /g surface area) and microbial diversity (Chao1 = 888.09; Shannon = 8.09). AWB, despite lower microbial richness (Chao1 = 333.40), sustained bioelectricity via hydrophilic functional groups (─OH, ─NH₂), favoring Aeromonas dominance (45.87% abundance). Microbial analysis identified Proteobacteria (60.41%–74.66%) and Firmicutes (1.29%–12.89%) as key electroactive phyla, with genera Pseudomonas (up to 24.08%) and Aeromonas driving electron transfer. CSB exhibited intermediate performance, limited by lamellar pore structure and reduced microbial diversity (Shannon = 6.83). The findings demonstrate that biochar feedstock critically influences PMFC performance: RSB optimizes microbial diversity and electroactivity, while AWB leverages hydrophilicity for drought resilience. This study advances sustainable bioenergy strategies by linking biochar properties to microbial‐electrogenic synergies, offering pathways to enhance PMFC efficiency in water‐stressed environments.