Using urea to improve the ORR performance of N-, P-, and S-ternary-doped porous carbon derived from biomass

Although biomass-derived metal-free electrocatalysts for oxygen reduction reaction (ORR) have garnered increasing attention, their ORR performance is lower than that of commercial 20% Pt/C. To improve their ORR performance, a series of porous carbons with high [Formula: see text] contents are prepared by pyrolyzing a mixture of spinach leaf powder and urea at different mass ratios (1:0, 1:5, 1:10, and 1:15) at a high temperature; the resultant materials are labeled as S-850, S-850-5, S-850-10, and S-850-15, respectively. The results indicate that the [Formula: see text] contents in the as-synthesized S-850, S-850-5, S-850-10, and S-850-15 products are 5.43, 5.74, 5.93, and 5.93 at%, respectively, which gradually increase with increasing urea contents, while the [Formula: see text] and [Formula: see text] contents (0.7 and 0.3 at%, respectively) show no change. Among all the as-synthesized products, the sample obtained by the addition of 10 wt.% urea (S-850-10) exhibits the best ORR catalytic performance in an O 2 -saturated 0.1 M KOH solution with a half-potential of 0.748 V and a diffusion-limited current density of −4.76 mA cm[Formula: see text] at 0.4 V. The half-potential and diffusion-limited current density of S-850-10 are improved by 0.53% and 8.61% compared to those of S-850 (0.744 V and −4.35 mA cm[Formula: see text] at 0.4 V, respectively). These findings indicate that urea can be used as an [Formula: see text] resource to increase the [Formula: see text] content of biomass-derived metal-free porous carbon, enhancing its ORR performance.