Fig. 7. Power and durability performance of N-G-CNT with the addition of KB in PEM fuel cells.

(A) Polarization curves of N-G-CNT with loadings: 2, 0.5, or 0.15 mg cm⁻² plus KB (2 mg cm⁻²) for each cathode. Weight ratio of (N-G-CNT/KB)/Nafion, 1:1. (B) Cell polarization and power density as a function of gravimetric current for N-G-CNT/KB (0.5/2 mg cm⁻²) with a 1:1 weight ratio of (N-G-CNT/KB)/Nafion. (C) Durability of the metal-free N-G-CNT in a PEM fuel cell measured at 0.5 V, compared with a Fe/N/C catalyst. Catalyst loading of N-G-CNT/KB (0.5 mg cm⁻²) and Fe/N/C (0.5 and 2 mg cm⁻²). Test conditions: H₂/O₂; 80°C; 100% relative humidity; back pressure, 2 bar. [From J. Shui, M. Wang, F. Du, L. Dai, N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells. Sci. Adv. 1, e1400129 (2015). Reprinted with permission from AAAS.]