Microbial-photoelectrochemical cell for the conversion of raw cellulose materials into electrical power and chemicals.

Exploiting biomass as a fuel source has attracted increasing attention over the last few decades. Combined biotic-abiotic systems can enhance conversion efficiency, but biotic reactions often require oxygen-free conditions, which are hindered by oxygen evolution at the photoanode. Herein, we develop a modular microbial-photoelectrochemical cell (MPEC) that facilitates the one-pot degradation and light-induced conversion of cellulosic material into electrical power and added-value compounds. A BiVO4 photoanode functionalized with cobalt phosphate (BiVO4/CoP) was engineered to suppress undesired competing reactions, while enhancing the selectively photooxidation of small organic molecules such as glucose. The anaerobic cellulolytic bacteria, Clostridium thermocellum, convert the insoluble cellulose matter to yield varied saccharides, mainly cellobiose, which are subsequently oxidized by the BiVO4/CoP photoanode to generate photocurrents. The MPEC demonstrated excellent operational stability for at least three days, maintaining a photocurrent density of ∼400 μA cm-2. During activation, ethanol (10.7 mM), acetic acid (1.2 mM), and formic acid (2.1 mM) were detected. The performance of the developed MPEC was validated using real-world waste substrates, including Citrus maxima leaves and industrial paper, demonstrating its versatility and robustness. This approach integrates photoelectrochemical energy generation with microbial cellulose degradation, offering a sustainable and practical platform for converting biomass into electrical energy and valuable chemicals.