Effect of Mo2C-functionalized electrode interface on enhancing microbial cathode electrocatalysis: Beyond electrochemical hydrogen evolution

Mo2C has recently been introduced into microbial cathode electrocatalysis due to its well-known catalytic ac-tivity for hydrogen evolution reaction (HER), but a low electrode potential (i.e., a high energy input) is required usually. However, in the range of potential where HER cannot occur, its effect on microorganism/cathode interfacial kinetics remains unknown. Herein, an active Mo2C interface is constructed on conventional carbon cloth electrode to investigate its impact on electric-driven fumarate reduction by a typical electroactive micro-organism (Shewanella oneidensis MR-1) at a potential of-0.36 V (vs. standard hydrogen electrode) that cannot meet the HER requirement. The Mo2C-functionalized electrode achieves a greatly increased current consumption density of-0.041 mA cm-2, about three times that of the control, indicating a faster fumarate reduction rate. This substantially proves that the enhancement of microbial electrocatalytic kinetics at Mo2C-functionalized interface is not confined to the induced hydrogen evolution. By analyzing its interaction with extracellular electron transfer mediators (e.g., c-type cytochromes and riboflavin), a robust inward extracellular electron transfer process based on the rapid electrochemical reaction of riboflavin at the Mo2C-functionalized interface is elaborated. This work provides a new understanding of the mechanism by which the nanostructured Mo2C interface enhances microbial cathode electrocatalysis.

Automated summary

Mo2C has been used in microbial cathode electrocatalysis for hydrogen evolution reaction (HER), but its effect on microorganism/cathode interfacial kinetics in the absence of HER remains unknown. In this study, an active Mo2C interface was constructed on a carbon cloth electrode to investigate its impact on fumarate reduction by a typical electroactive microorganism. Results show that the Mo2C-functionalized electrode significantly improves the fumarate reduction rate, indicating enhanced microbial electrocatalytic kinetics. The interaction between Mo2C and extracellular electron transfer mediators is analyzed, providing a new understanding of the mechanism behind the enhancement.