Mechanism and preparation research of binary heteroatom co-doped (X = N, S, P) platinum/carbon black electrocatalysts for an enhanced oxygen reduction reaction via a one-pot pyrolysis method

Abstract

Due to the depletion of fossil fuels and environmental concerns, hydrogen fuel cells and proton exchange membrane fuel cells emerge as vital alternatives for sustainable energy. Currently, there is a lack of comprehensive understanding and experimental validation regarding the effects of different heteroatom dopants (e.g., N, P, and S) and their combinations on platinum-based catalysts. In this study, a simple one-pot synthesis approach is employed to synthesize Pt-based catalysts supported on heteroatom-doped carbon black. The oxygen reduction performance of these catalysts is evaluated, and the influence of pyrolysis temperature, Pt loading, and the type and amount of heteroatom dopants on the distribution and catalytic activity of Pt in the catalysts is thoroughly investigated. Experimental and theoretical calculations reveal that the incorporation of three types of heteroatoms, namely N, S, and P, exerts varying degrees of impact on the composition and particle size of Pt-based catalysts. The E_o and E_1/2 of the Pt/BP-N₂₅₀S₂₅₀-900-30% catalyst were found to be 0.962 V vs. RHE and 0.821 V vs. RHE, respectively, surpassing those of other N, S, and P co-doped catalysts, indicating enhanced activity due to N-doping. Additionally, the S-doped Pt/BP-N₂₅₀S₂₅₀-900-30% catalyst exhibits superior stability, with only a 40 mV decrease in E_1/2 after 5000 cycles of CV testing compared to a 52 mV decrease observed for the commercial Pt/C catalyst. However, the presence of platinum–phosphorus species results in adverse effects on the oxygen reduction process. This facile one-pot synthesis approach for heteroatom-doped carbon supported Pt-based catalysts offers new insights for the scalable production of fuel cell catalysts.