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

Abstract

Mo2C has recently been introduced into microbial cathode electrocatalysis due to its well-known catalytic activity 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 microorganism (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.