On-Chip Investigation of Electrocatalytic Oxygen Reduction Reaction of 2D Materials

The on-chip electrocatalytic microdevice (OCEM) is an emerging platform specialized in the electrochemical investigation of single-entity nanomaterials, which is ideal for probing the intrinsic catalytic properties, optimizing performance, and exploring exotic mechanisms. However, the current catalytic applications of OCEMs are almost exclusively in electrocatalytic hydrogen/oxygen evolution reactions with minimized influence from the mass transfer. Here, an OCEM platform specially tailored to investigate the electrocatalytic oxygen reduction reaction (ORR) at a microscopic level by introducing electrolyte convection through a microfluidic flow cell is reported. The setup is established on gold microelectrodes and later successfully applied to investigate how Ar-plasma treatment affects the ORR activities of 2H MoS2. This study finds that Ar-plasma treatment significantly enhances the ORR performance of MoS2 nanosheets owing to the introduction of surface defects. This study paves the way for highly efficient microscopic investigation of diffusion-controlled electrocatalytic reactions.