Nitrogen and phosphorus co-doped carbon networks derived from shrimp shells as an efficient oxygen reduction catalyst for microbial fuel cells

The waste shrimp shells (SS) were used as both carbon and nitrogen sources to directly synthesize N and P co-doped carbon networks with abundant mesopores and high specific surface area by simple acid pretreatment and carbonization. Using exogenous phosphorus as dopant, the prepared catalyst (PA-SS 900) favorably possessed a high oxygen reduction reaction (ORR) activity regarding half-wave potential (0.82 V) and limiting current (4.47 mA cm−2), which approached those of commercial 20 wt% Pt/C. For practical application in microbial fuel cell (MFC), the N, P co-doped PA-SS 900 achieved a maximum power density (MPD) of 802 mW m−2 and an open circuit voltage (OCV) of 653 mV, which also were close to that (892 mW m−2 and 752 mV) based on 20% Pt/C as cathode catalyst. Remarkably, the synthetic catalyst had a better long-term stability than that of 20% Pt/C in alkaline medium. These results demonstrated that N, P co-doped PA-SS 900 was an accessible and efficient ORR catalyst in air-cathode MFC for relatively desirable energy generation and wastewater treatment. Further, the direct utilization of waste shrimp shells replacing chitin or chitosan in energy conversion is worthy of in-depth study due to the advantages of simple process, environmental friendliness and availability.