Shuang Wang, Chun Hong Mak, Shella Permatasari Santoso, Wenxin Niu, Jiun-Tai Chen, Chunyan Tan, Ji-Jung Kai, Carol Sze Ki Lin, Hsien-Yi Hsu
Understanding microbial responses to electrode interfacial characteristics is essential for establishing electrode design principles to enhance bioelectrochemical system (BES) performance. Biochar, with its rich surface physicochemical properties, offers an advantage for investigating microbial adaptation behaviour, whereas electrochemical analysis for elucidating these processes is rarely explored. Here, three biochar interfaces that exhibit characteristic differences in pore architecture, surface functional groups, wettability, and graphitisation degree were used to investigate the distinction in microbial attachment, extracellular polymeric substance (EPS) secretion, and extracellular electron transfer (EET) kinetics. The results showed: (1) accessible open macropores (>50 nm) facilitate cell clustering; (2) oxygen- and nitrogen-containing functional groups, such as O–C–O, C O, pyrrolic-N, and amine-N species improve surface hydrophilicity, further promoting active microbial attachment and enhanced secretion of tryptophan-rich EPS; (3) bioanodes with EPS-enriched biofilms and highly graphitised carbon frameworks exhibit accelerated heterogeneous electron transfer kinetics and enhanced interfacial electron diffusion. Consequently, these coupled interfacial characteristics collectively enable enhanced BES performance, delivering a maximum power density of 196.47 mW m–2 and a COD removal efficiency of 50.65% within 72 h. This work highlights the significant value of electrochemical approaches for investigating how interfacial chemistry regulates microbial attachment, EPS secretion, and EET efficiency, thereby affecting BES performance. Furthermore, the comprehensive interfacial characteristics identified in this study provide useful mechanistic insights for the future design of bioelectrodes for practical wastewater treatment. © 2026 Elsevier Ltd.
School of Energy and Environment, City University of Hong Kong, Kowloon Tong, Hong Kong; Department of Materials Science and Engineering, Centre for Functional Photonics (CFP), City University of Hong Kong, Kowloon Tong, Hong Kong; Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong; Department of Chemical Engineering, Faculty of Engineering, Widya Mandala Surabaya Catholic University, Kalijudan No. 37, East Java, Surabaya, 60114, Indonesia; Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan; Shenzhen Research Institute of City University of Hong Kong, Shenzhen, 518057, China