Tuning strain effect and surface composition in PdAu hollow nanospheres as highly efficient ORR electrocatalysts and SERS substrates

Although palladium-gold (PdAu) bimetals have been extensively investigated as oxygen reduction reaction (ORR) electrocatalysts, the comprehensive mechanism studies on the strain and electronic effect are in their infancy. Herein, the strain effect and surface composition of PdAu hollow nanospheres (PdAu HSs) can be tuned by Pd-to-Au ratio. The optimal ORR performance can deliver the half-wave potential of 0.866 V versus reversible hydrogen electrode (vs. RHE) even superior to commercial Pt/C, which can be attributed to sufficient strain effect, local micro-electric field and the adsorption strength of oxygen-containing species in moderation. In addition, surface-enhanced Raman scattering (SERS) performances further supported the variation trend of surface composition. The enhancement factor (EF) of Au HSs can reach 3.8 x 10(5), further indicating its great potential as efficient SERS substrates for analysis and detection applications.