The enhancement of microbial fuel cell performance by anodic bacterial community adaptation and cathodic mixed nickel-copper oxides on a graphene electrocatalyst

Dena Z Khater; R S Amin; M O Zhran; Zeinab K Abd El-Aziz; Mohamed Mahmoud; Helmy M Hassan; K M El-Khatib

doi:10.1186/s43141-021-00292-2

The enhancement of microbial fuel cell performance by anodic bacterial community adaptation and cathodic mixed nickel-copper oxides on a graphene electrocatalyst

J Genet Eng Biotechnol. 2022 Jan 24;20(1):12. doi: 10.1186/s43141-021-00292-2.

Authors

Dena Z Khater¹, R S Amin¹, M O Zhran², Zeinab K Abd El-Aziz², Mohamed Mahmoud³, Helmy M Hassan⁴, K M El-Khatib⁵

Affiliations

¹ Chemical Engineering & Pilot Plant Department, Engineering and Renewable Energy Research Institute, National Research Centre, 33 El-Buhouth St., Dokki, Cairo, 12311, Egypt.
² Faculty of Science (Girls), Botany and Microbiology Department, Al-Azhar University, Nasr City, Cairo, Egypt.
³ Water Pollution Research Department, National Research Centre, 33 El-Buhouth St., Dokki, Cairo, 12311, Egypt.
⁴ Microbial Chemistry Department, National Research Centre, 33 El-Buhouth St., Dokki, Cairo, 12311, Egypt.
⁵ Chemical Engineering & Pilot Plant Department, Engineering and Renewable Energy Research Institute, National Research Centre, 33 El-Buhouth St., Dokki, Cairo, 12311, Egypt. kamelced@hotmail.com.

Abstract

Background: Although microbial fuel cells (MFCs) represent a promising technology for capturing renewable energy from wastewater, their scaling-up is significantly limited by a slow-rate cathodic oxygen reduction reaction (ORR) and the development of a resilient anodic microbial community. In this study, mixed transition metal oxides of nickel and copper (Ni and Cu), supported on a graphene (G) (NiO-CuO/G) electrocatalyst, were synthesized and tested as a cost-effective cathode for ORR in MFCs. Electrochemical measurements of electrocatalyst were conducted using a rotating disk electrode (RDE) and linear sweep voltammetry (LSV) in a neutral electrolyte, and compared with a benchmark Pt/C catalyst. Furthermore, the long-term performance of the as-synthesized electrocatalyst was evaluated in a single-chamber MFC by measuring organic matter removal and polarization behavior. The successful enrichment of electroactive biofilm was also monitored using transmission electron microscopy and the Vitek2 compact system technique.

Results: When compared with the benchmark platinum cathode, the NiO-CuO/G electrocatalyst exhibited high selectivity toward ORR. The rotating disk electrode (RDE) experiments reveal that ORR proceeds via a 4-electron ORR mechanism. Furthermore, the NiO-CuO/G electrocatalyst also exhibited a high power density of 21.25 mW m^-2in an air-cathode MFC, which was slightly lower than that of Pt/C-based MFC (i.e., 50.4 mW m^-2). Biochemical characterization of the most abundant bacteria on anodic biofilms identified four genera (i.e., Escherichia coli, Shewanella putrefaciens, Bacillus cereus, and Bacillus Thuringiensis/mycoides) that belonged to Gammaproteobacteria, and Firmicutesphyla.

Conclusions: This study demonstrates that the NiO-CuO/G cathode had an enhanced electrocatalytic activity toward ORR in a pH-neutral solution. This novel mixed transition metal oxide electrocatalyst could replace expensive Pt-based catalysts for MFC applications.

Keywords: Activated sludge; Electrocatalyst; Linear Sweep Voltammetry; Microbial fuel cell; NiO–CuO/G.