Grain Boundary Triggered Basal Plane Active Sites in Mn-Doped Pd Nanosheets for Boosting Oxygen Reduction Reaction

Two-dimensional Pd-based nanosheets have aroused intense research interests as a promising catalyst for oxygen reduction reaction (ORR); nevertheless the electrocatalytic performance is still far from satisfactory due to the lack of basal plane active sites. Herein, the grain boundary (GB) engineering strategy and doping strategy are adopted to construct GB-rich Mn-doped Pd nanosheets (GB-PdMn NSs) via a one-pot wet chemical approach. Benefiting from the synergistic effect between the localized tensile strain aroused by GBs and electronic structure modification by Mn doping, GB-PdMn NSs exhibit a high mass activity of 2.65 A mg^-1 at 0.90 V (vs RHE), which is 12.62 times higher than that of commercial Pt/C in alkaline media, together with a superior stability up to 10 000 potential cycles. <i>In situ</i> Raman spectroscopy investigations certify that GBs enhance the direct adsorption capacity of O₂ and facilitate OOH* adsorption-desorption dynamics. Experimental results combined with theoretical calculations indicate that the localized lattice strain near the GBs can trigger the basal plane inert sites in Mn-doped Pd NSs, thereby optimizing the overall potential barrier for the entire ORR pathway. This work provides useful guidance for the synthesis and accurate modulation of Pd-based electrocatalysts with abundant active sites and high intrinsic activity.