Spatial separation of the reduction center (photosystem I) and oxidation center (photosystem II) is an obvious characteristic of natural photosynthesis. Enlightened by this natural process, a simple material based on silica-sphere-supported Pt nanoparticles (SSP) was designed as a freestanding hydrogen evolution center for semiconductor photocatalysts. In situ photoluminescence characterization showed that the radiation recombination of electron–hole pairs in semiconductors (i.e. TiO2 and CdS) was well suppressed due to the presence of SSP. And the quenching efficiency increases with the hydrogen evolution rate of photocatalysts. These results indicated that SSP could effectively trap electrons from the photoexcited semiconductors during collision between SSP and semiconductor, and then complete the hydrogen evolution reaction over the Pt nanoparticles. Detailed investigation also showed that the performance of SSP was influenced by several factors, including the particle size of the silica sphere and the physical and chemical states of Pt nanoparticles. Besides, it was demonstrated that the loaded metal was not limited to Pt. Pd, Ni and Au can also be used as active sites in this freestanding cocatalyst strategy.

The activity and stability of CdS for visible-light-driven hydrogen evolution could be significantly enhanced by embedding plasmonic Au nanoparticles. The plasmon resonance energy field of Au nanoparticles could increase the formation rate and lifetime of e−/h+ pairs in CdS semiconductors.

MgFe2O4 with inverse spinel structure is demonstrated to be an efficient support for constructing practical potential Pt catalyst (Pt/MgFe2O4). The resultant Pt/MgFe2O4 exhibits excellent catalytic behavior in CO oxidation under normal temperature and humidity. TOF calculated based on the content of Pt is 0.131 s–1. The excellent performance of Pt/MgFe2O4 attributes to the presence of surface undercoordinated lattice oxygens on MgFe2O4 support. These oxygens could participate in the initial CO oxidation and then be recovered under O2 conditions. Over this Pt/MgFe2O4 catalyst, CO catalytic oxidation should mainly follow a redox mechanism.Keywords: CO oxidation; MgFe2O4; nanoparticle; O2 activation; supported Pt catalyst

Based on a simple colloid deposition method, a series of Pt/FeOx catalysts were prepared using 3–4 nm Pt colloid nanoparticles and FeOx with different microstructures (i.e. the structure and surface properties). The FeOx support was obtained via a thermal treatment method, which enables the tailoring of FeOx from ferrihydrite to α-Fe2O3, and the amount of hydroxides on the surface of FeOx decreases gradually with the phase change. Over optimized Pt/FeOx, CO could be completely converted at room temperature (298 K) and a relatively high space velocity (1.2 × 105 mL g−1 h−1). The correlation between the microstructure of the FeOx support and the CO oxidation performance of the resultant Pt/FeOx catalyst was investigated. Although the oxidation of Pt nanoparticles is inevitable in the Pt loading process, relatively large amounts of Pt0 species can be preserved on the FeOx support possessing abundant surface hydroxides. In situ DRIFTS shows that the surface hydroxides on FeOx could also participate in the catalytic process; they could react with CO adsorbed on Pt0 sites and then recover easily in the co-presence of molecular oxygen and water gas. These results show that the intrinsic properties of the FeOx support not only affect the oxidation state of supported Pt nanoparticles in the preparation process, but also provide new active sites in the catalytic process. FeOx supports possessing abundant surface hydroxides are suitable for preparing high-performance Pt/FeOx catalysts for low-temperature CO oxidation.

A silica-supported CdS nanoparticle photocatalyst exhibits excellent visible-light driven H2 evolution activity without the use of a cocatalyst. The apparent quantum yield can reach 42% under 420 nm light illumination.

A kind of mesoporous carbon support with abundant surface functional groups and a tunable pore size was prepared using a modified hard-template route. This carbon support was demonstrated to be efficient for fabricating ultrafine iron oxide catalysts, and the resultant catalysts exhibit an obviously higher activity in air oxidation of several benzyl alcohols compared with the catalysts with other synthetic carbon as supports. The concrete role of carbon support in the catalyst design was investigated in detail. The negatively charged surface oxygen functional groups serve as strongly active sites for anchoring positively charged Fe3+ ions and lead to high dispersion of iron oxide species. These oxygen functional groups also provide a suitable coordinate environment to increase the electron density of iron centres and form efficient active sites for the oxidation of benzyl alcohols with molecular oxygen.

Highly dispersed iron oxide supported catalysts, prepared using HNO3-treated CMK-3 mesoporous carbons as supports, exhibit relatively high catalytic activity in selective oxidation of benzyl alcohol with oxygen.

•Graphite oxides with different microstructure were prepared via thermal treatment.•The structure changes from multilayer sheets to an ultrathin 2D structure.•The amount of oxygen-containing groups decreases upon temperature increasing.•Surface carboxylic groups act as active sites for the oxidation of benzyl alcohol.A series of graphite oxide (GO) materials were obtained by thermal treatment of oxidized natural graphite powder at different temperatures (from 100 to 200 °C). The microstructure evolution (i.e., layer structure and surface functional groups) of the graphite oxide during the heating process is studied by various characterization means, including XRD, N2 adsorption, TG–DTA, in situ DRIFT, XPS, Raman, TEM and Boehm titration. The characterization results show that the structures of GO materials change gradually from multilayer sheets to a transparent ultrathin 2D structure of the carbon sheets. The concentration of surface COH and HOCO groups decrease significantly upon treating temperature increasing. Benzyl alcohol oxidation with air as oxidant source was carried out to detect the catalytic behaviors of different GO materials. The activities of GO materials decrease with the increase of treating temperatures. It shows that the structure properties, including ultrathin sheets and high specific surface area, are not crucial factors affecting the catalytic activity. The type and amount of surface oxygen-containing functional groups of GO materials tightly correlates with the catalytic performance. Carboxylic groups on the surface of GO should act as oxidative sites for benzyl alcohol and the reduced form could be reoxidized by molecular oxygen.

A series of carbon-supported CaO materials, prepared using different porous carbon materials as supports, were tested as basic catalysts for the transesterification of triacetin with methanol and characterized by means of X-ray diffraction (XRD), N2 adsorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). It was found that all of the carbon-supported CaO catalysts are active for the transesterification reaction, and their catalytic performance can be influenced by a variety of factors, such as the types of carbon supports, the concentration of impregnated CaO, the heat-treated temperatures of the catalysts, and the reaction temperatures. Particularly, the supported CaO catalyst, which is prepared using a kind of porous carbon (NC-2) as a support, exhibits very high activity, stability, and recyclability. We suppose that the main characteristics of this porous carbon, such as the presence of relatively abundant surface oxygen-containing functional groups and well-developed porosity, may be beneficial to build a suitable interaction between CaO particles and the carbon support, thus resulting in the formation of an active and stable catalyst system.

A kind of mesoporous carbon support with abundant surface functional groups and a tunable pore size was prepared using a modified hard-template route. This carbon support was demonstrated to be efficient for fabricating ultrafine iron oxide catalysts, and the resultant catalysts exhibit an obviously higher activity in air oxidation of several benzyl alcohols compared with the catalysts with other synthetic carbon as supports. The concrete role of carbon support in the catalyst design was investigated in detail. The negatively charged surface oxygen functional groups serve as strongly active sites for anchoring positively charged Fe3+ ions and lead to high dispersion of iron oxide species. These oxygen functional groups also provide a suitable coordinate environment to increase the electron density of iron centres and form efficient active sites for the oxidation of benzyl alcohols with molecular oxygen.

A silica-supported CdS nanoparticle photocatalyst exhibits excellent visible-light driven H2 evolution activity without the use of a cocatalyst. The apparent quantum yield can reach 42% under 420 nm light illumination.

The activity and stability of CdS for visible-light-driven hydrogen evolution could be significantly enhanced by embedding plasmonic Au nanoparticles. The plasmon resonance energy field of Au nanoparticles could increase the formation rate and lifetime of e−/h+ pairs in CdS semiconductors.

Enhancing the efficiency of semiconductor photocatalysts is still a challenging issue for photocatalytic hydrogen evolution. In this work, a synergistic strategy of surface defects and spatial bandgap engineering was realized for constructing a Zn1−xCdxS/SiO2 photocatalyst. A quantum efficiency of 48.6% (at 420 nm) for hydrogen evolution was obtained without the use of a cocatalyst. The molar ratio of Cd:Zn in Zn1−xCdxS particles could be gradually tuned from 0.305:1 (inside) to 0.490:1 (outside). At least a 0.17 eV potential difference is present between the inside and outside of Zn1−xCdxS particles. Experimental and theoretical analyses showed that photogenerated electrons and holes could vectorially transfer along the spatial bandgap to reach the surface, and be trapped by the surface defects. In situ formed surface Cd species act as the active sites accelerating the surface hydrogen evolution reaction.

CeO2 nanorods anchored on mesoporous carbon exhibit high activity and stability in aerobic oxidative coupling of alcohols and amines to imines. The abundant surface Ce3+ and the suitable interaction between CeO2 nanorods and the carbon support should be responsible for the excellent catalytic behaviors.

Highly dispersed iron oxide supported catalysts, prepared using HNO3-treated CMK-3 mesoporous carbons as supports, exhibit relatively high catalytic activity in selective oxidation of benzyl alcohol with oxygen.

Based on a simple colloid deposition method, a series of Pt/FeOx catalysts were prepared using 3–4 nm Pt colloid nanoparticles and FeOx with different microstructures (i.e. the structure and surface properties). The FeOx support was obtained via a thermal treatment method, which enables the tailoring of FeOx from ferrihydrite to α-Fe2O3, and the amount of hydroxides on the surface of FeOx decreases gradually with the phase change. Over optimized Pt/FeOx, CO could be completely converted at room temperature (298 K) and a relatively high space velocity (1.2 × 105 mL g−1 h−1). The correlation between the microstructure of the FeOx support and the CO oxidation performance of the resultant Pt/FeOx catalyst was investigated. Although the oxidation of Pt nanoparticles is inevitable in the Pt loading process, relatively large amounts of Pt0 species can be preserved on the FeOx support possessing abundant surface hydroxides. In situ DRIFTS shows that the surface hydroxides on FeOx could also participate in the catalytic process; they could react with CO adsorbed on Pt0 sites and then recover easily in the co-presence of molecular oxygen and water gas. These results show that the intrinsic properties of the FeOx support not only affect the oxidation state of supported Pt nanoparticles in the preparation process, but also provide new active sites in the catalytic process. FeOx supports possessing abundant surface hydroxides are suitable for preparing high-performance Pt/FeOx catalysts for low-temperature CO oxidation.