Anode surface modification with reduced graphene oxide (rGO) and molybdenum (Mo) enhances microbial diversity and chemical oxygen demand (COD) removal in microbial fuel cells

This study aimed to investigate the effects of anode surface modifications on microbial community composition and chemical oxygen demand (COD) removal efficiency in microbial fuel cells (MFCs). Four different anode electrodes were fabricated: bare nickel foam (NF), reduced graphene oxide-coated nickel foam (NF/rGO), and NF/rGO modified with 30 wt% and 50 wt% molybdenum (Mo). These electrodes were tested in a single-chamber, membraneless, air-cathode MFC. Surface morphology was characterized using scanning electron microscopy (SEM), and microbial diversity was assessed through 16S rRNA metagenomic sequencing. Distinct microbial profiles were observed across the electrode types. The NF anode supported high abundances of Mesoterricola sediminis (22.2%), Klebsiella pneumoniae (10.1%), and other facultative species. The NF/rGO electrode promoted colonization by Cutibacterium acnes (8.1%) and Paracidovorax avenae (5.4%). On the NF/rGO/30%Mo electrode, notable species included Escherichia coli (8.4%) and Salmonella enterica (6.0%). The NF/rGO/50%Mo anode exhibited the highest microbial diversity, with species such as Streptomyces sp. RerS4 (6.9%) and Micromonospora endophytica (6.5%) being predominant. The highest COD removal efficiency (88.58%) was achieved using the NF/rGO/50%Mo anode. These findings demonstrate that molybdenum-modified rGO coatings enhance both microbial colonization and electrochemical performance, offering a promising strategy for improving MFC efficiency in wastewater treatment applications.