Biochar-based Electrodes and Catalysts for Microbial Fuel Cells: Engineering Strategies, Mechanisms, and Performance
Abstract
Microbial fuel cells (MFCs) require low-cost, durable electrodes to replace conventional carbon materials and precious-metal catalysts. Biochar, a carbon-rich product of biomass pyrolysis, has emerged as a sustainable alternative for both electroactive anodes and oxygen-reduction reaction (ORR) cathode catalysts. Its tunable pore structure, surface chemistry, and renewable feedstocks can reduce costs while improving electrochemical performance. Free-standing biochar anodes also avoid polymeric binders that increase resistance, block active sites, and reduce durability. As a cathode catalyst, biochar can be tailored to favor either the four-electron ORR pathway for higher power generation in conventional and photosynthetic MFCs or the two-electron pathway for in situ H2O2 production in bioelectro-Fenton (BEF) MFCs. This review critically summarizes recent progress in biochar engineering for MFCs by relating feedstock composition, pyrolysis conditions, and modification methods to physicochemical properties and electrochemical behavior. It compares powder-based and free-standing biochar anodes, examines biochar cathode catalysts for ORR control, and discusses techno-economic, environmental, and future perspectives for rational electrode design.
摘要
微生物燃料電池（MFCs）需要低成本、高耐久性的電極材料，以取代傳統碳材與貴金屬觸媒。生物炭（Biochar）做為生質熱解之碳富產物，已成為電活性陽極與氧還原反應（ORR）陰極觸媒之永續替代方案。其可調控之孔隙結構、表面化學性質及可再生原料，不僅能降低成本，亦能提升電化學性能。無黏結劑自支撐型生物炭陽極，亦可避免高分子黏結劑所帶來之電阻增加、活性位點堵塞與耐久性下降等問題。做為陰極觸媒時，生物炭可被設計以優先選擇四電子 ORR 路徑（用於傳統與光合微生物燃料電池以提升功率輸出），或選擇二電子路徑（用於生物電化學芬頓 MFC 以現場產生 H₂O₂）。本综述系统性地回顧了生物炭於 MFCs 之最新進展，串聯原料組成、熱解條件及修飾策略，與其物理化學性質及電化學行為之關聯，並比較粉末型與自支撐型生物炭陽極、探討生物炭陰極觸媒之 ORR 控制，同時討論技術經濟、環境影響與未來展望。
🔬 重要發現
生物炭為 MFCs 永續替代电极材料：生物炭来源广泛（农业废弃物等），可透过热解条件调控其孔隙结构、表面官能基团与导电性，兼具低成本与可持续性优势。
Biochar serves as a sustainable, low-cost alternative to conventional carbon electrodes and precious-metal catalysts in MFCs.
热解条件决定生物炭特性：原料组成与热解温度直接影响生物炭的比表面积、孔隙率、表面化学与导电性，进而决定其电化学性能表现。
Feedstock composition and pyrolysis conditions directly govern biochar's surface area, porosity, surface chemistry, and conductivity, dictating electrochemical performance.
无黏结剂自支撑阳极优于粉末涂覆：自支撑型生物炭阳极可避免 Nafion、PVA、PVDF 等黏结剂堵塞活性位点、升高内阻与降低耐久性的问题。
Free-standing biochar anodes outperform binder-assisted powder coatings by avoiding resistance increase, active site blockage, and reduced durability.
异原子掺杂与金属纳米粒子提升催化活性：氮、硫等异原子掺杂可调控碳骨架电子结构；金属纳米粒子（Fe、Co 等）可增强电容、引入活性位点并防止孔隙堵塞。
Heteroatom doping and metal nanoparticle incorporation tune electronic structure, enhance capacitance, introduce active sites, and prevent pore clogging.
ORR 路径选择因 MFC 类型而异：传统/光合 MFCs 需 4e⁻ ORR 路径最大化功率；生物电化学芬顿 MFCs 需 2e⁻ ORR 路径产 H₂O₂ 降解污染物。
Conventional/photosynthetic MFCs require 4e⁻ ORR for power; BEF-MFCs rely on 2e⁻ ORR for in situ H₂O₂ production in pollutant degradation.
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