A P–O functional group anchoring Pt–Co electrocatalyst for high-durability PEMFCs

Abstract

Bimetallic Pt–M (M = transition metals) nanoparticles are promising for the development of proton exchange membrane fuel cells (PEMFCs), but their applications are limited by inevitable nanoparticle aggregation due to the Ostwald ripening process during the cathodic oxygen reduction reaction (ORR). Here, we report a novel strategy involving the incorporation of P–O functional groups into the pore channels of Ketjen carbon black (KB), which serves as a linkage to anchor PtCo alloy nanoparticles on the carbon support surface (denoted as PtCo/P_2.73O_x–KB). We develop a liquid phase in situ XRD cell to investigate the nanoparticle growth and Co dissolution of PtCo nanoparticles during the ORR process. The results indicate that the introduction of P–O functional groups can effectively inhibit the growth of nanoparticles due to the strong interaction between Pt in nanoparticles and O of P–O in carbon support, as supported by DFT calculations. The mass activity of PtCo/P_2.73O_x–KB decreased by 24.3% after 30 000 potential cycles, while that of commercial Pt/C dropped by 37.5%. H₂–air PEMFCs employing PtCo/P_2.73O_x–KB as the cathode delivers a high power density of 1.21 W cm⁻² at 3.1 A cm⁻² (with a cathode loading of 0.1 mg_Pt cm⁻²) and a negligible cell voltage loss at 0.8 A cm⁻² after 30 000 potential cycles between 0.60 and 0.95 V, surpassing the DOE 2025 target. Furthermore, this P–O functional group-anchoring strategy is also valid for other Pt–M (M = Fe, Ni, Cu, Zn) alloy catalysts, further enhancing ORR stability.