The underlying mechanism trade-off between particle proximity effect and low-Pt loading for oxygen reduction and methanol oxidation reaction activity

Abstract

Highly efficient and stable Pt-based electrocatalysts have broad application prospects in fuel cells, among which, Pt loading accompanied with particle size, interparticle distance (ipd), and interaction with support are identified as key contributors for high activity and selectivity. Herein, we have developed the nitrogen-doped graphite-like carbon sheets supporting low-Pt loading (Pt@N-GC) with uniform size and controllable ipd, and disentangled the main effect of ipd on oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) activity. The optimal 5.0 wt% low-Pt loading results in more abundant Pt sites and lower ipd, which leads to the higher surface reactivity by proximity effect, and 2e− pathway can be hindered by strongly resorbing and reducing H2O2 to promote 4e− pathway towards ORR. Simultaneously, the 5.0 wt% Pt@N-GC can effectively improve the MOR activity, enhance the adsorption of -OH group under the appropriate ipd, so as to promote the instantaneous oxidation of CO and enhance the tolerance, and accelerate the oxidative dehydrogenation of methanol. Benefiting by the synergistic effect of Pt nanoparticles and N-GC support, all Pt@N-GCs exhibit bifunctional electrocatalytic activity and durability. We believe the gained trade-off of the loading and proximity effect of Pt, and its influence on catalytic activity and selectivity contributes to design more promising low-Pt loading bifunctional catalysts for fuel cell.