Fig. 20. (a) Scheme of the reaction where the Pt SECM tip approaches the electrocatalyst to observe the feedback from the sample and substrate, as well as the O₂ diffusion from the substrate/catalyst interface to the tip. (b and c) SG/TC results, with the tip polarized at 0.3 V vs. RHE for driving the ORR, while the substrate was scanned in the OER region at 5 mV s⁻¹. The tip was in proximity to N–Co–Mo–GF/CNT on (b) GC and (c) Ni substrates. Reproduced from ref. 51 with permission from American Chemical Society © 2020. https://pubs.acs.org/doi/abs/10.1021/acscatal.0c00352. Further permissions related to this material should be directed to the American Chemical Society.