Enhancing CO tolerance via molecular trapping effect: Single-atom Pt anchored on Mo₂C for efficient alkaline hydrogen...

Developing highly efficient, stable, and CO-tolerant electrocatalysts for hydrogen oxidation reaction (HOR) remains a critical challenge for practical proton/anion exchange membrane fuel cells. Here in, an atomically dispersed platinum (Pt) on Mo₂C nanoparticles supported on nitrogen-doped carbon (Pt_SAMo₂C-NC) with a unique yolk-shell structure is presented as a highly efficient and stable catalyst for HOR. The Pt_SAMo₂C-NC catalyst demonstrates remarkable HOR performance, with a high exchange current density of 2.7 mA cm^-2 and a mass activity of 2.15 A/mg_Pt at 50 mV (vs. RHE), which are 1.5 and 18 times greater than those of the 40 % commercial Pt/C catalyst, respectively. Furthermore, the unique Pt_SAMo₂C-NC structure exhibits superior CO tolerance at H₂/1,000 ppm CO, significantly outperforming commercial Pt/C catalysts. Density functional theory (DFT) calculations indicate that the introduction of Mo₂C forms a strong electronic interaction with Pt, which decreases the electron density around the Pt atoms and shifts the d-band center away from the Fermi level. This results in a reduction of the *H adsorption energy and an optimization of the *OH adsorption energy in Pt_SAMo₂C-NC. In addition, by calculating the CO adsorption energy, it was found that Mo₂C exhibits strong CO adsorption ability, which generating a molecular trapping effect, thereby protecting the Pt active sites from poisoning. The strong metal-support electronic interaction significantly enhances the catalytic activity, stability, and CO tolerance of the material, providing a new strategy for developing catalysts with these desirable properties.