Highly Porous Fe_xMnO_y Microsphere as an Efficient Cathode Catalyst for Microbial Electrosynthesis of Volatile Fatty Acids from CO₂

Abstract

Microbial electrosynthesis (MES) can efficiently convert CO2 into valuable chemicals. A biocathode, which plays central role in MES process, is expected to have very high surface area and catalytic activity to derive the cathodic reaction flawlessly. In this study, a highly porous bimetallic FexMnOy (x=1, 2 and y=3, 4) microsphere was synthesized and applied as cathode catalyst in a single chamber MES. MES having FexMnOy exhibited higher net acetate production rate (204 mM/m2d) and coulombic efficiency (58 %) than the MES without catalyst (180 mM/m2d and 34 %). The excellent performance of MES with FexMnOy was attributed to the high Brunauer‐Emmett‐Teller (BET) surface area (around 278 m2/g) with rough surface and efficient electron transfer from cathode to microorganism promoted by FexMnOy complex. The cathode with FexMnOy reduced charge transfer resistance by ∼70 % and enhanced the exchange current density by 7.2‐times compared to plain cathode. This study suggests that FexMnOy can be used as the highly efficient and low‐cost catalyst on cathode of scaled up MESs.

Copper foam supported g-C3N4-metal–organic framework bacteria biohybrid cathode catalyst for CO2 reduction in microbial electrosynthesis

“… MES type Cathode materials Microbe Imposed potential/V vs. Ag/AgCl* Products Acetate production, g/L.d CE, % Refs. Dual chamber Chitosan on carbon cloth S. Ovata − 0.4 Acetate 0.32 86 68 Dual chamber 3D Iron oxide carbon felt S. Ovata − 0.69 Acetate 0.24 86 69 Dual chamber Mo 2 C-CF Mixed culture − 0.85 Acetate 0.19 64 70 Dual-chamber Graphene–nickel foam Mixed cultures − 0.85 Acetate 0.013 70 71 Single-chamber Fe x MnO y Mixed culture − 0.8 Acetate and iso-butyrate 0.38 58 33 Single-chamber g- C 3 N 4 -MOF biohybrid Mixed culture − 0.8 Acetate and iso-butyrate 0.75 95 …”

“…A recent investigation employing porous Fe x MnO y displayed a robust interaction with microorganisms. This led to an increase in current density in MES, reaching 2.5 times higher values compared to control MES setups lacking modified cathodes 33 . Similarly, an MES utilizing a porous framework gas diffusion electrode (GDE) exhibited enhanced current density, achieving 6 A/m 2 34 .…”

“…Similarly, an MES utilizing a porous framework gas diffusion electrode (GDE) exhibited enhanced current density, achieving 6 A/m 2 34 . Although these porous materials have exhibited positive effects on current uptake in MESs, their constrained surface area (e.g., 278 m 2 /g in Fe x MnO y 33 and 230–454 m 2 /g in GDE 35 ) has hindered extensive biofilm development. Thus, to address this, the exploration of novel materials with larger surface areas becomes imperative.…”

H2 mediated mixed culture microbial electrosynthesis for high titer acetate production from CO2

“…Recognizing that H 2 -mediated VFAs production in MES can boost productivity and overcome the electrochemical surface barrier, developing efficient H 2 production and conversion processes is critical for scaling and applying the MES technology in the real world. Studies have tested a variety of cathode and catalyst materials to improve H 2 production, including carbon felt coated with Pt NPs/rGO, TiO 2 , MoC and Rh, Fe x MnO y , Si wafer coated with CoP, MoS 2 , and NiMo, and nickel hollow fiber coated with nanotube [ 11 , [16] , [17] , [18] , [19] ]. In many cases, the increased H 2 production didn't necessarily correspond with higher VFAs concentrations and might result in low Faradaic efficiency due to insufficient H 2 utilization.…”

Optimum Magnetite–Zeolite Nanoparticles Loading on the Cathode of Microbial Electrochemical–Anaerobic Digestion System for Enhancing Methane Generation

“…In some recent studies, electron exchange between electrode and microbe was enhanced cathode modified with conductive materials such as carbon nanotube, [ 15 ] graphene, [ 16 ] and metal oxides. [ 17,18 ] Tian et al proposed that the coenzyme F420 relevant to the methanogenesis was improved in the presence of the conductive additives on the cathode, and thus enhanced methane production was achieved. [ 19 ] Lately, magnetite‐based materials have been of great interest among researchers due to their excellent physical and chemical properties such as being highly biocompatible for microbes, electrically conductive to accelerate electron transfer, high availability, and low cost.…”