Revealing the Correlation of Loading-to-Performance of Single Atom Catalysts

The correlation between metal loading and overall catalytic performance remains elusive for single-atom electrocatalysts (SACs), which hinders the oriented optimization of active site densities and scalable synthesis of them. To effectively address this issue, Ru single atoms with different loading are anchored on the graphene-like framework and tungsten carbide substrate (WC_1-x) to investigate the synergistic effect among different local configurations. X-ray absorption spectroscopy demonstrated that the loading of Ru atoms critically governs the interatomic distance between adjacent metal active sites at second shell coordination. In situ Raman spectroscopy shows that WC_1-x nanoparticles can break the hydrogen bond network by reorienting H₂O molecule adsorption and promoting the availability of active H₂O among electrode-electrolyte interface. Density functional theory (DFT) calculations demonstrated that the moderate distance between active sites could further lower the reaction barrier and enhance the catalytic activity. Consequently, the optimal sample Ru-WC_1-x with 0.76 wt% Ru loading exhibits a low overpotential of 7 mV at 10 mA⋅cm^-2 and the anion exchange membrane electrolyzer to stably operate for 100 h at 1 A⋅cm^-2. Such correlation of spatial effects between different active sites were universally demonstrated in similar systems anchored with either Pt, Ir, or Co elements.