Hofmann-type MOFs derived small-sized Pt nanoparticles embedded in S, N codoped carbon matrix for enhanced oxygen reduction reaction

Developing efficient and durable platinum-based catalysts for the oxygen reduction reaction (ORR) is a major challenge. In this work two Platinum-Zinc Hofmann-type Metal-Organic Frameworks are synthesized by ligand regulation, one with 4,4′-dipyridyl disulfide introducing sulfur and the other with 4,4′-azopyridine as a sulfur-free analogue. After pyrolysis, the sulfur-containing precursor yields small Pt nanoparticles embedded in a sulfur and nitrogen co-doped carbon matrix (Pt/SNC), while the sulfur-free precursor forms intermetallic L1₀-PtZn on nitrogen-doped carbon (L1 0 -PtZn/NC). Zn evaporation and S/N co-doping in Pt/SNC optimize Pt dispersion, tune electronic structures, and strengthen Pt–carbon interactions, whereas the absence of sulfur stabilizes the L1₀-PtZn phase. Pt/SNC shows much smaller particle sizes (~4.98 nm) than L1 0 -PtZn/NC (~10.61 nm) and exhibits the best ORR performance with a half-wave potential of 0.88 V, surpassing Pt/C (0.86 V) and L1 0 -PtZn/NC (0.79 V). Its specific and mass activities are 1.6/1.8 times higher than Pt/C and 2.85/6.4 times higher than L1 0 -PtZn/NC. Durability tests confirm that Pt/SNC retains 78 % of its mass activity after 60,000 cycles. These results demonstrate the effectiveness of ligand regulation and S/N co-doping in designing high-performance Pt-based electrocatalysts.