Why and how to tailor the vertical coordinate of pore size distribution to construct ORR-active carbon materials?

Abstract

Pore size distribution and specific surface area of carbon-based materials are extensively reported to play a key role in catalyzing oxygen reduction reaction (ORR). As far as pore size distribution is concerned, carbon materials with the same pore size ranges always show different ORR performances. Why? It is well accepted that there are two coordinates for pore size distribution, horizontal and vertical ones. The former is related to the pore size range and studied maturely, and the latter is closely related to the quantity of any kind of specific pores (including meso-/micro-/macro-pore) contributed to the pore volume or area, i.e., the variation of the vertical coordinate of pore size distribution is closely linked to the variation of the meso-/micro-/macro-pore volumes, which should make great contribution to the mass transfer and density of ORR active sites of carbon materials and never be reported. Herein, this work synthesizes a series of N, P co-doped micro/mesoporous carbon materials with tunable/unalterable/negligible meso-/micro-/macro-pore volumes to pioneer the relationship of the mesopore volume on behalf of the vertical coordinate of pore size distribution with the - mass transfer and ORR active site density of such metal-free heteroatom-doped porous carbon materials and investigate why and how to tailor the coordinates of pore size distribution to construct ORR-active carbon materials i.e., the mass transfer and density of ORR active site are improved via tailoring the vertical coordinate of pore size distribution. We also develop a universal pore-forming strategy for extensively synthesizing carbon materials with expected pore size range (horizontal coordinate) and mesopore volume (vertical coordinate) from widely available biomass in nature to guide the synthesis and selection of carbon-based ORR-active materials to meet the demands of high-performance ORR electrocatalysts.