A photo-bio-hybrid catalyst with a triple synergistic enhancement effect to boost oxygen reduction for high-performance biofuel cells

Abstract

Bilirubin oxidase (BOD)-catalyzed oxygen reduction reaction (ORR) exhibits outstanding advantages compared to abiotic electro-catalysts in neutral environment, thus playing a crucial role in fuel cells. However, limited by the low solubility of oxygen and the impeded extracellular electron transfer, the activity of BOD is fast-approaching its upper threshold. Given this, we create a mutually enhanced bio-abiotic hybrid ORR photo-electro-catalyst by integrating BOD with pyrrole nitrogen-doped carbon nanodots (BOD/N_pyo-CDs). In BOD/N_pyo-CDs, N_pyo-CDs generate photoelectrons and vacancies under illumination, and the vacancies and BOD simultaneously accept electrons from the anode. The photoelectrons can rapidly transfer to BOD's active center due to the high electron conductivity of N_pyo-CDs and well-matched energy level, further boosting the ORR on BOD. This process promotes photoelectrons-vacancies separation of N_pyo-CDs and reduces fluorescence energy dissipation, which in turn promotes the ORR by generating more photoelectrons. Thanks to the triple synergistic promotion effect, the current density of BOD/N_pyo-CDs reaches 2.76 mA cm⁻². Coupled with an Au nanozyme anode, we develop a glucose/oxygen fuel cell with remarkable power output (468 μW cm⁻²) and high stable open-circuit voltage (0.78 V, 70 h). This study shed light on breaking the limitation in energy conversion efficiency by creating a mutually promoted bio-abiotic catalyst.