Formation of monometallic Au and Pd and bimetallic Au–Pd nanoparticles confined in mesopores via Ar glow-discharge plasma reduction and their catalytic applications in aerobic oxidation of benzyl alcohol

Au–Pd bimetallic nanoparticles confined in SBA-15 are superior to Au and Pd monometallic catalysts for selective benzyl alcohol oxidation. The plasma reduction outperforms the H2 thermal reduction, showing modified morphology and surface chemistry of metal nanoparticles, as well as enhanced catalytic performance. Successfully prepared via Ar glow-discharge plasma reduction, Au–Pd bimetallic nanoparticles were highly active in the selective oxidation of benzyl alcohol, showing a rate constant of 0.50h−1, which was 12.5 and 2× that of Au and Pd monometallic catalysts, respectively. Characterization analyses attributed the enhancement in both activity and selectivity to a Pd-rich shell/Au-rich core structure with abundant surface-coordination-unsaturated Pd atoms of those effectively confined and well-dispersed Au–Pd nanoparticles. As a green, efficient, and safe protocol, plasma reduction outperformed conventional H2 thermal reduction due to the different particle nucleation and growth mechanism, which afforded modified morphology and surface chemistry of metal nanoparticles. Further oxidation and re-reduction of plasma-reduced Au–Pd catalyst resulted in the atomic rearrangement of nanoparticles, leading to inferior catalytic performance.