Functionalizing carbon nanofibers with chicken manure to catalyse oxygen reduction reaction in a fuel cell

Chicken manure (CM) is one of the most common animal wastes produced worldwide. The conventional application of CM is as a fertilizer; however, in the present study, we introduce an approach for the straightforward and affordable use of CM for fuel cell applications. It reports the functionalization of carbon nanofibers (CNFs) using CM to confer multiple functionalities. The elements that make up the functionalized CNF are nitrogen (7.40%, atoms ratio, the same below), oxygen (6.22%), phosphorous (0.30%), and sulfur (0.02%), etc., according to energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy studies. It has been verified that following treatment with CM, the morphology of the CNFs remains the same. The CM-modified CNFs exhibit a higher electrocatalytic activity (onset potential: −0.0756 V; limiting current density: 2.69 mA/cm²) for the oxygen reduction reaction (ORR) at the cathode of a fuel cell. The electron transfer number for this sample is 3.68, i.e., the ORR favours a four-electron pathway like Pt/C. The direct method of functionalizing the CNF is more effective; however, treatment of CNFs with Triton X-100 prior to functionalization shields their otherwise exposed open edge sites and in turn affects their ORR activity. A large surface area (99.866 m²/g), the presence of multiple functional elements (oxygen, nitrogen, phosphorous, sulfur, etc.), surface charge redistribution and induced donor–acceptor interactions at the surface of CM-modified CNFs contribute to their enhanced electrochemical activity. This preliminary study reports the suitability of a facile and economical approach for treating CM for the most advanced clean energy applications. Hopefully, this study will pave the way for cutting-edge methods for handling other biowaste materials as well.

Graphical abstract