Emission of PAHs from a single hydrogen-oxygen pem fuel cell: In relation to fuel cell carbon materials

Abstract

This study investigates the emissions of polycyclic aromatic hydrocarbons (PAHs) from a single hydrogen-oxygen proton exchange membrane (PEM) fuel cell (FC) and its relation to FC carbon materials. The results show that the magnitude of specific areas or pore volumes followed the order BP2000 > XC-72R > XC-72 > Alfa for carbon blacks and multi-walled carbon nanotube (MWCNT) > single-walled carbon nanotube (SWCNT) for CNTs. Nap and high carcinogenic potency species (BaP, DBA, and IND) were dominant in almost all tested carbon materials (carbon black, CNT, carbon cloth (CC), waterproof CC (WPCC), and waterproof carbon paper (WPCP), except mesophase graphite powder (MGP)). Of all the tested carbon materials, both SWCNT and MWCNT showed the (same) highest BaP content (67.0 μg g-1). Similar 21-PAH concentration profiles were observed for XC-72 vs. XC-72R, SWCNT vs. MWCNT, or CC vs. WPCC, consistent with the results of cluster analysis. The results of the principle component analysis (PCA) showed that two main factors were responsible for the 21-PAH concentration profiles. The Total-PAHs content of the tested carbon materials ranged from 2573 ± 333 (MGP) to 10.2 ± 0.51 (WPCP) μg g-1, while their Total-BaPeq values were in the order MWCNT (155 ± 3.61 μg g-1) ≈ SWCNT >> WPCC > MGP > Alfa ≈ XC-72 > XC-72R >> CC > BP2000 ≈ WPCP (1.13 ± 0.01 μg g-1). The emission concentrations of Total-PAHs were lower from the anode (gas emission: 4360 ± 72 ng Nm-3 and water effluent: 277 ± 79 ng L-1) than from the cathode (gas emission: 6904 ± 443 ng Nm-3 and water effluent: 572 ± 104 ng L-1). Likewise, the Total-BaPeq concentration (dominated by 5/6/7-ring PAHs) was also lower in anode (640 ± 2.07 ng Nm-3) than in cathode gas emissions (967 ± 8.02 ng Nm-3); however, those in the anode and cathode water effluents were similar (5.70 ± 5.64 and 5.60 ± 4.88 ng L-1, respectively). Accordingly, the H2-O2 PEMFC is not a complete zero-emission power generator when considering its PAH emissions during operation.