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We showed earlier that using Au nanoparticles of ca.3.5 nm for the cores to construct core–shell Au@NimPt2nanostructures can be promising for developing high performance Pt catalysts for the oxygen reduction reaction (ORR) in acidic electrolytes (L.-L. Shen, G.-R. Zhang, S. Miao, J. Liu and B.-Q. Xu, ACS Catal., 2016, 6, 1680–1690). By varying the nanosize of Au cores (d= 2.2–10.3 nm) and the atomic Pt/Au (or Ni/Au) ratio (m= 0.5–6), serial Au-d@NimPtmnanostructures are herein constructed and characterized comprehensively to investigate effects of the Au-core size and NiPt-shell thickness on the Pt activity for the ORR. Maximization of the Pt intrinsic activity (IAPt) to as high as ca.1.06 mA cmPt−2at 0.9 V (vs.RHE) is observed on Au-d@Ni2Pt2of d= 7.7 and 10.3 nm, 4-fold higher than that of conventional Pt/C (E-TEK). Construction of Au-2.2@NimPtmsamples by variation of mdemonstrates that the formation of an integrated NiPt-shell of suitable thickness is essential for improving IAPt, whose number appears to correlate with the reduction potential of oxidized surface Pt (or surface Pt–O). The integrated NiPt-shell is also shown to be crucial to the catalytic durability of Pt during the ORR. These observations are discussed in terms of surface faceting, strain and electronic effects in association with the Au cores.

Transfer hydrogenation of α,β-unsaturated aldehyde is an important reaction (MPV reaction) for the synthesis of allyl alcohol because of its high selectivity for the hydrogenation of the carbonyl group. This reaction can proceed over many oxide catalysts but the role of acidic and basic sites on the oxide catalyst surface has remained an issue of debate. We report herein the catalytic data of serial Al2O3and SiO2–Al2O3catalysts for the MPV reaction of cinnamaldehyde at 150 °C using 2-propanol as the H-donor. The surface acidity of the catalysts is adjusted by changing the calcination temperature between 400 and 1000 °C and quantified to correlate with the catalyst performance. Surface Lewis acidic sites that are poisoned by pyridine but not by hindered pyridine (lutidine) under catalyst working conditions are identified as the catalytic sites for the MPV reaction. Lutidine-sensitive surface Brønsted acidic sites, which are among the spectator sites during the MPV reaction, are shown to serve as the catalytic sites for cascade cross-etherification reaction between cinnamyl alcohol and 2-propanol. The MPV reaction is also conducted under high-pressure CO2, the results of which exclude possible involvement of surface basic sites during the reaction.

Effects of the crystalline structure and surface property of the Al2O3support on the NOxstorage and reduction (NSR) performance of Pt–BaO/Al2O3catalysts were studied using catalysts prepared from a series of Al2O3samples obtained by varying the calcination temperature of an Al(OH)3hydrogel in the range of 450–1000 °C (referred to as the pre-calcination temperature, PCT). The texture, crystalline structure and surface acidity of the Al2O3(PCT) supports were measured employing nitrogen adsorption–desorption, XRD, NH3-TPD and IR spectroscopy of adsorbed pyridine, respectively. The Al2O3(PCT) samples showed a gradual ordering of the γ-Al2O3phase when increasing the PCTfrom 450 to 800 °C, and a phase transition from the γ- to -Al2O3phase upon further increasing the PCTto 1000 °C. The surface density of Lewis acid sites of the Al2O3(PCT) samples exhibited a maximum at PCTin the range of 800–900 °C. The NSR performance of Pt–BaO/Al2O3catalysts derived from the Al2O3(PCT) samples was studied under cyclic lean/rich conditions. The numbers of NOxstored and reduced on the Pt–BaO/Al2O3(PCT) catalysts showed similar volcano-type dependencies on PCT, peaking at PCT= 800 °C. The origins of the support PCTeffect were discussed in the light of Pt particle size, the nature of BaO sites and Pt–BaO synergy. It was found that the increase in the crystallinity of the γ-Al2O3phase and the surface acid site density of the supporting Al2O3samples would result in improved proximity and synergy between Pt and BaO sites, leading to much more efficient NSR Pt–BaO/Al2O3catalysts.