Low-loading platinum–cobalt electrocatalyst supported on hollow carbon for enhanced oxygen reduction reaction

The oxygen reduction reaction (ORR) at the cathode of proton exchange membrane fuel cells is very slow. Therefore, platinum (Pt)-based catalysts are only used in practical applications. However, due to the high cost of Pt-based noble electrocatalysts, research is underway to reduce the use of noble metals or replace Pt-based noble catalysts. To reduce the total production cost of catalysts in fuel cells, a simple mass production process is required and the use of noble metals should be reduced. Metal–organic framework (MOF)-derived non-noble metal electrocatalysts have been extensively investigated as ORR catalysts due to their large surface area and open pore structure. However, MOF-based non-noble metal catalysts exhibit low catalytic activity and stability compared to commercial Pt-based catalysts. To address this problem, a small amount of precious metal is added to MOFs to enhance the performance of MOF-based electrocatalysts. In this study, we synthesized an ultra-low-loading Pt electrocatalyst (2.2- wt% Pt) supported on MOF-derived hollow Co, nitrogen-doped carbon (h-Co-NC). h-Co-NC was prepared by carbonizing the MOF@MOF core–shell structure. After carbonization, Pt was loaded using the polyol method, and a hollow and single-atomic Pt/h-Co-NC electrocatalyst was successfully synthesized by annealing. The synthesized hollow Pt/h-Co-NC electrocatalyst exhibited superior ORR performance and stability compared with non-hollow Pt/Co-NC.