Rational design of graphene biohydrogel as a modular platform for highly efficient starch‐to‐bioelectricity

Chemical‐to‐bioelectricity by using different biocatalysts was considered as a next‐generation green power source. However, bioelectricity production using macromolecular substrate usually encountered low Coulombic efficiency (CE) and power density due to inefficient electron releasing and sluggish electron collection. Here, a rationally engineered biocascade (including depolymerization module, fermentation module, and electro‐respiration module) embedded in highly conductive 3D graphene hydrogel (electron collection module) was designed and fabricated as a modular platform to simultaneously improve the substrate degradation, enhance the electron releasing and reinforce the electron collection. As a result, this modular platform enabled a ~15‐fold improvement on power density and reached the highest CE (46.3%) and power density (780 mW/m2) ever reported for bioelectricity production from starch (a model macromolecular substrate). This work demonstrated a promising approach for rationally harvesting bioelectricity with complicated substrates, which would open up a new avenue for practical applications.