Solar Photothermal Electrodes for Highly Efficient Microbial Energy Harvesting at Low Ambient Temperatures

Abstract Temperature is an important parameter for the performance of bioelectrochemical systems (BESs). Energy‐intensive bulk water heating has been usually employed to maintain a desired temperature for the BESs. This study concerns a proof‐of‐concept of a light‐to‐heat photothermal electrode for solar heating of a local electroactive biofilm in a BES for efficient microbial energy harvesting at low temperatures as a replacement for bulk water heating approaches. The photothermal electrode was prepared by coating Ti 3 C 2 T x MXene sunlight absorber onto carbon felt. The as‐prepared photothermal electrode could efficiently raise the local temperature of the bioelectrode to approximately 30 °C from low bulk water temperatures (i.e., 10, 15, and 20 °C) under simulated sunlight illumination. As a result, highly efficient microbial energy could be harvested from the low‐temperature BES equipped with a photothermal electrode without bulk water heating. This study represents a new avenue for the design and fabrication of electrodes for temperature‐sensitive electrochemical and biological systems.