Polyaniline-copper composite: A non-precious metal cathode catalyst for low-temperature fuel cells

Platinum has been used extensively in low-temperature fuel cells (LTFCs), including polymer electrolyte fuel cells and microbial fuel cells (MFCs). Still, its replacement with low-cost alternatives has been a matter of considerable conjecture for some time. This study investigates the possible use of an electrochemically synthesized CP/PANi-Cu cathode as a low-cost replacement for a Pt cathode in MFCs and LTFCs. Thorough and detailed characterization and evaluation of the CP/PANi-Cu cathode was undertaken by electrochemical and advanced surface analytical methods, including scanning electron microscopy (SEM), XPS, FTIR, 4-D X-ray microscopy, and 3D profilometry. Direct comparison of the proposed cathode with a CP/Pt cathode is used to justify its adequacy as a replacement for a platinum cathode. The PANi-Cu coating had a uniform nano-fibrous structure, which enhanced its performance as a cathode. In particular, the incorporation of copper into the coating enhanced its ORR activity. By comparison, the optimum CP/PANi-Cu cathode achieved a 170% higher j_0apparent of 0.088 ± 0.003 mA cm^–2 than obtained with a standard CP/Pt cathode with a Pt loading of 0.5 mg cm^–2. Even when a higher Pt loading of 1.5 mg cm^–2 was used, the CP/PANi-Cu cathode performance was still slightly better. The superiority of the CP/PANi-Cu cathode was also reflected in the obtained R_ct value of 1.456 Ω cm^–2 compared with 3.95 and 1.485 Ω cm^–2 obtained with the CP/Pt cathode, which has a Pt loading of 0.5 and 1.5 mg cm^–2, respectively. The results obtained by SEM, XPS, FTIR, 4D X-ray microscopy, and 3D profilometry confirmed the unique nature, composition, and presence of copper in the CP/PANi-Cu composite. The results of this study clearly demonstrate that the proposed CP/PANi-Cu cathode can be adopted as a suitable low-cost replacement for a Pt cathode in LTFCs.