Strong metal‐support interaction boosting the catalytic activity of Au/TiO_(2) in chemoselective hydrogenation

Gold catalysts have been reported as highly effective catalysts in various oxidation reactions.However,for chemoselective hydrogenation reactions,gold‐based catalysts normally show much lowercatalytic activity than platinum group metals,even though their selectivities are excellent.Here,wereport that the chemoselective hydrogenation activity of 3‐nitrostyrene to 3‐vinylaniline overAu/TiO_(2)can be enhanced up to 3.3 times through the hydrogen reduction strategy.It is revealedthat strong metal‐support interaction,between gold nanoparticles(NPs)and TiO_(2)support,is introducedthrough hydrogen reduction,resulting in partial dispersion of reduced TiOx on the Au surface.The partially covered Au not only increases the perimeter of the interface between the gold NPs andthe support,but also benefits H_(2)activation.Reaction kinetic analysis and H_(2)‐D2 exchange reactionshow that H_(2)activation is the critical step in the hydrogenation of 3‐nitrostyrene to 3‐vinylaniline.Density functional theory calculations verify that hydrogen dissociation and hydrogen transfer arefavored at the interface of gold NPs and TiO_(2)over the hydrogen‐reduced Au/TiO_(2).This study providesinsights for fabricating highly active gold‐based catalysts for chemoselective hydrogenationreactions.

Effects of Au nanoparticle size and metal-support interaction on plasmon-induced photocatalytic water oxidation

Plasmonic photocatalysis with tunable light absorption has aroused significant attention in so-lar-to-chemical energy conversion.However,the energy conversion efficiency of plasmonic photo-catalysts is impeded by ineffective charge separation and the lack of highly active sites for redox reactions.In this work,the Au nanoparticle size and Au-TiO2 interaction of the Au/TiO2 plasmonic photocatalyst were adjusted simultaneously using a post-calcination treatment.The visi-ble-ight-induced water oxidation activity exhibited a volcano-like relationship with the calcination temperature;the treated photocatalyst at 600°C manifested the highest activity.Characterization with UV-visible spectra,XRD,SEM,and XPS revealed that the effect of the Au nanoparticle size and Au-TiO2 interaction were both responsible for the increase in plasmon-induced water oxidation activity.

Photo-induced self-formation of dual-cocatalysts on semiconductor surface

Cocatalyst plays key roles in photogenerated charge separation and surface catalytic reactions in photocatalysis.However,it is not clear if the chemical states of cocatalysts changed or remains unchanged under photocatalytic reaction conditions.Herein,taking NaTaO3 as an example,we systemically investigated the chemical states of nickel‐based cocatalysts during photocatalytic water splitting reaction.It was found that photo‐induced self‐formation of Ni and NiO cocatalyst species take place on the surface of NaTaO3 nanocrystals.The self‐formation of dual‐cocatalysts not only occurs on 26‐facet NaTaO3,but also takes place on a more general 6‐facet NaTaO3.Our work clarified that the chemical states of cocatalysts are changing and the redox dual‐cocatalysts are redistributed on the semiconductor surface owing to the reaction induced by photogenerated charges under the condition of photocatalytic reactions.

Selective and stable Au-Cu bimetallic catalyst for CO-PROX

Gold-based catalysts are promising in CO preferential oxidation(CO-PROX)reaction in H_(2)-rich stream on account of their high intrinsic activity for CO elimination even at ambient temperature.However,the decrease of CO conversion at elevated temperature due to the competition of H_(2)oxidation,together with the low stability of gold nanoparticles,has posed a dear challenge.Herein,we report that Au-Cu bimetallic catalyst prepared by galvanic replacement method shows a wide temperature window for CO total conversion(30-100℃)and very good catalyst stability without deactivation in a 200-h test.Detailed characterizations combined with density functional theory(DFT)calculation reveal that the synergistic effect of Au-Cu,the electron transfer from Au to Cu,leads to not only strengthened chemisorption of CO but also weakened dissociation of H_(2),both of which are helpful in inhibiting the competition of H_(2)oxidation thus widening the temperature window for CO total conversion.