Live microalgal cells modified by L-cys/Au@carbon dots/bilirubin oxidase layers for enhanced oxygen reduction in a membrane-less biofuel cell

Electrochemical oxygen reduced reaction (ORR) is a critical element in clean energy development. Despite efforts to enhance gas transfer to the reaction interface, the low solubility of O-2 molecules and slow diffusion rate in liquid electrolyte is still a significant challenge. Herein, we design an artificial outer membrane on microalgal cells, which consists of a carbon dots/bilirubin oxidase (CDs/BOD) ORR catalyst layer and a L-cystine/Au nanoporous O-2 supply layer. O-2 generated by photosynthesis from microalgal cells then can be directly transported to the CDs/BOD catalytic interfaces, overcoming the sluggish gas transfer in the electrolyte. Thus, the cathode constructed by the fabricated microalgal cells realizes an ORR current density of 655.2 mu A/cm(2) with fast ORR kinetics, which is 2.68 times higher than that of a BOD cathode fed with pure O-2. A membrane-less glucose/O-2 biofuel cell is further developed using the hybrid artificial cells as the cathode, and the power density is 2.39 times higher than that of a BOD cathode biofuel cell in O-2 saturated solution. This biomimetic design supplies O-2 directly to the carbon dots/BOD catalyst layer from the microalgae membrane through a nanoporous L-cys/Au layer, providing an alternative solution for the transfer barrier of O-2 in the electrolyte.

Automated summary

An artificial outer membrane is designed on microalgal cells to enhance the efficiency of oxygen reduced reaction (ORR). The membrane allows the direct transportation of oxygen generated by photosynthesis to the catalytic interfaces, improving the ORR kinetics. The microalgal cell cathode achieves a higher current density compared to a cathode fed with pure oxygen, and a membrane-less glucose/O2 biofuel cell using the hybrid artificial cells as the cathode demonstrates a higher power density.