Micropipet delivery-substrate collection mode of scanning electrochemical microscopy for the imaging of electrochemical reactions and the screening of methanol oxidation electrocatalysts

The micropipet delivery-substrate collection (MD-SC) mode of scanning electrochemical microscopy (SECM) is demonstrated. This new mode is intended for the study and imaging of electrochemical as well as electrocatalytic reactions of neutral species that cannot be generated electrochemically. The spontaneous transfer of the analyte from an organic solvent across an interface between two immiscible electrolyte solutions (ITIES) and its diffusion into the aqueous solution served as the mechanism to deliver it to the substrate, where the corresponding electrochemical or electrocatalytic reaction is carried out. High-resolution SECM images of ferrocenemethanol (FcMeOH) oxidation, benzoquinone (BQ) reduction, and the formic acid oxidation reaction (FAOR) at a Pt microelectrode substrate were successfully acquired. Furthermore, this new mode was used for the screening of electrocatalyst arrays for the methanol oxidation reaction (MOR), with the optimization of an efficient candidate, Pt₈₀Ce₂₀. Digital simulations produced quantitative information about the expected current response at the substrate in the proposed MD-SC mode of SECM.