Solvent-free synthesis of N-doped nanoporous carbon materials as durable high-performance pH-universal ORR catalysts

Metal-free carbons as durable high-performance oxygen reduction electrocatalysts, deemed to be promising alternatives to the platinum-group metals (PGMs), are vital to large-scale commercialization of fuel cells. Herein, a solvent-free synthetic strategy has been proposed to prepare N-doped nanoporous metal-free carbonaceous materials originating from various types of plant residues (papaya skin - fruit, bamboo shoot - forestry, wheat straw - farming and cabbage stem - vegetable). The optimal metal-free carbon, possessing maximized reaction surface area and optimized distributions of nanopore structures and nitrogen species, can function as the durable high-performance pH-universal ORR electrocatalyst, reaching or surpassing the benchmark 20% Pt/C catalyst within the wide scope of pH. This paper substantiates the solvent-free, scalable and bio-universal preparation approach to converting various biomass wastes into durable high-performance pH-universal ORR carbonaceous catalysts, capable of expanding the repertoire of cathode catalysts employed by fuel cells that demand diverse pH environments.