Plasmonic Catalysis on Au-Pd Nanoalloy for Self-Hydrogen Transfer Hydrogenolysis of Lignin β-O-4 Models under Visible Light

In the present study, we combined plasmonic Au and catalytically active Pd to develop a new photocatalyst of Au-Pd nanoalloy supported on ZrO2 nanopowder. Plasmonic catalysis was conducted on Au-Pd nanoalloy using visible light to cleave the C-O ether bond of lignin beta-O-4 linkage. The generated hot electrons decreased the apparent activation energy of this reaction and enabled it to proceed at mild conditions. A beta-O-4 dimer model, 2-phenoxy-1-phenylethanol, was effectively cleaved (98% conversion) to acetophenone (95% yield) and phenol (92% yield) under visible light at 80 degrees C for 24 h. This reaction occurred through a self-hydrogen transfer hydrogenolysis pathway. The dehydrogenation at the C-alpha position generated a "hydrogen pool" on Au-Pd, which will insert into the beta-O-4 linkage to cleave the C-O ether bond. The photocatalyst could well maintain its activity after recycling. This study provides a new photocatalytic procedure for solar energy utilization and lignin valorization.