Trimodal Hierarchical Porous Carbon Nanoplates with Edge Curvature for Faster Mass Transfer and Enhanced Oxygen Reduction

Abstract

Although hierarchical porous carbon materials have been widely used for electrocatalysis, the role of curvature in carbon nanostructures during electrochemical reactions remains poorly understood due to a lack of experimental models featuring clearly defined curved geometries and periodic structures. In this study, we fabricate hierarchical porous cobalt- and nitrogen-containing carbon nanoplates with trimodal porosity (macro-, meso-, and micropores) and continuous, homogeneous curved edges (Co/N-CNP-CURV) using a polystyrene-directed templating approach. The Co/N-CNP-CURV catalyst exhibits excellent catalytic activity and stability for the alkaline oxygen reduction reaction, with a half-wave potential of 0.82 V and a minimal potential shift of 8 mV after 5000 cycles. The enhanced electrocatalytic activity is attributed to synergistic combinations of the trimodal porosity, abundant Co–N_x active sites, a high density of curved edges, and graphitic carbon encapsulated with cobalt nanoparticles. Density functional theory calculations reveal that the presence of curvature in Co/N-CNP-CURV is beneficial for enhancing the charge transfer from the catalyst to O₂, lowering the adsorption energy of O₂, and reducing the activation free energy barrier for the rate-determining step (*O₂ + (H⁺ + e^–) → *OOH). The study provides compelling experimental evidence supporting the critical role of the curvature effect in enhancing the electrocatalytic performance of nanoporous metal-containing carbon materials.