Many of the existing electrochemical catalysts suffer from poor selectivity, instability, and low exchange current densities. These shortcomings call for a comprehensive exploration of the catalytic processes at the fundamental nanometer length scale levels. Here we exploit infrared (IR) nanoimaging and nanospectroscopy to directly visualize catalytic reactions on the surface of Cu₂O polyhedral single crystals with nanoscale spatial resolution. Nano-IR data revealed signatures of this common catalyst after electrochemical reduction of carbon dioxides (CO₂). We discuss the utility of nano-IR methods for surface/facet engineering of efficient electrochemical catalysts.