# Electrochemical imaging of thermochemical catalysis

## TL;DR

The paper uses electrochemical imaging to study how different parts of a platinum catalyst affect chemical reactions involving formic acid and oxygen.

## Contribution

The study introduces a method to visualize and quantify how electrochemical half-reactions interact on a catalyst's surface during thermochemical redox reactions.

## Key findings

- Catalytic rates vary across different grains of a platinum catalyst during oxygen reduction and formic acid oxidation.
- Inter-grain cooperativity is observed through lateral current flows that couple active sites during thermochemical catalysis.
- Site-specific chemical interactions modify the electrochemical half-reactions when both reactants are present.

## Abstract

Thermochemical redox catalysis is critical to a wide array of key chemical transformations and can proceed via the coupling of two electrochemical half-reactions. This electrochemical mechanism is exemplified by the platinum-catalysed aerobic oxidation of formic acid, wherein the oxygen reduction reaction is coupled to the formic acid oxidation reaction. Here using scanning electrochemical cell microscopy, we show there are grain-dependent variations in catalytic rates for the oxygen reduction and formic acid oxidation reactions at a platinum catalyst. Quantitative spatially resolved images of catalytic rates imply inter-grain cooperativity during ensemble thermochemical catalysis via lateral current flows that galvanically couple disparate active sites. Moreover, by comparing current–potential profiles of the half-reactions in isolation and in the presence of both reactants, we reveal additional site-specific chemical interactions that modify the two constituent half-reactions. These studies establish a methodology that exposes how electrochemical half-reactions couple and interact across surface structures to enable redox transformations.

Several thermochemical redox reactions have been shown to operate via the coupling of electrochemical half-reactions. Here, scanning electrochemical cell microscopy is employed to image the variations in catalytic rate at different grains of polycrystalline platinum during aerobic formic acid oxidation.