Study of carbon dioxide sequestration and electricity generation by a new hybrid bioenergy system with the novelty catalyst

This paper proposed a hybrid bioenergy system to enhance CO₂ fixation and electricity generation through the integration of a single-chamber microbial fuel cell (MFC) and a columnar photobioreactor (PBR). In this hybrid system, microalgal photosynthesis can continuously supply O₂ to the cathode of MFC, and the elimination of dissolved oxygen is conducive to the improvement of CO₂ fixation efficiency. However, affected by microalgae solution, the power generation of this system is limited. To further improve power output, a series of Co-based ternary metallic metal–organic frameworks (tri-MOFs) with controllable metal ratios are produced. It can be adopted as an efficient oxygen reduction reaction (ORR) catalyst through a facile sulfuration-pyrolysis treatment. The ORR performances of MOFs-derived composites are fully evaluated in both alkaline and neutral environments. The proposed catalyst achieves comparable ORR activity and superior durability to the Pt/C, because the formation of a three-dimensional porous structure facilitates electron transport. Different cathode catalysts for the CO₂ fixation efficiency and power generation of PBR-MFC hybrid systems are studied. The results present below.(1) The maximum power density of MFCs in this paper (850 mW·m⁻²) indicates a rise of 59.5 % by this sample, comparing with the level of Pt/C (533 mW·m⁻²). The material costs are 1.8 $·g⁻¹, which is 95.8 % lower than the costs of Pt/C (42.65 $·g⁻¹). (2) Due to the enhanced consumption efficiency of dissolved oxygen and microalgae growth rate, the maximum CO₂ fixation efficiency and power density of in PBR-MFC hybrid bioenergy system can achieve 20.7 % and 404 mW·m⁻², respectively. The results obtained by cathodic MOFs-derived MFC with low cost and outstanding oxygen consumption efficiency, would provide a new sight on CO₂ fixation and bioenergy generation.