Progress of Biomass/Coal-Based Carbon Materials as Electrocatalysts for Oxygen Reduction Reaction

• • Platinum-based catalysts constitute up to 40% of total fuel cell system cost, driving the urgent need for non-precious alternatives; biomass/coal-derived carbons offer a cost-effective substitute with natural heteroatom doping. • • ORR proceeds via 4-electron, 3-electron, or 2-electron pathways; efficient catalysts favor the direct 4-electron route (rate constant k1) to minimize peroxide formation and enhance energy efficiency. • • The Wroblowa model describes two main pathways: direct 4-electron reduction (k1) and 2-electron peroxide pathway (k2, k3, k4, k5); catalyst design must suppress peroxide desorption (k5) to improve stability. • • Biomass/coal-based carbons can achieve high ORR activity through heteroatom doping (N, P, S) and pore structure engineering, with recent studies reporting onset potentials comparable to Pt/C in alkaline media.