Gengnan Li

Highly efficient formaldehyde elimination over meso-structured M/CeO2 (M = Pd, Pt, Au and Ag) catalyst under ambient conditions

A series of mesoporous CeO2 supported noble metal (Pt, Pd, Au and Ag) catalysts, fabricated through a facial pyrolysis and in situ reduction protocol, were used for formaldehyde elimination under ambient conditions. The materials possessed relatively high specific surface area and uniformly dispersed noble metal nanoparticles, and showed very high catalytic activities for formaldehyde oxidation. For about 1 wt% noble metal loaded materials, Pt/CeO2, Pd/CeO2 and Au/CeO2 catalysts could completely catalytically oxidize HCHO at room temperature. Even for the low activity Ag/CeO2 catalyst, the complete conversion temperature could reach 100 °C, much lower than that reported before. Such good catalytic properties could be attributed to the strong synergetic interaction between the active component and CeO2 nano-crystalline aggregated support. The reaction mechanism over the noble-metal/CeO2 catalyst was also discussed through in situ DRIFTS analysis.

A highly moisture-resistant Fe-doped mesoporous Co3O4 catalyst for efficient low-temperature CO oxidation

Spinel-type Co3O4 has been reported to be the only transition metal oxide to date, which exhibits excellent catalytic activity for low temperature CO oxidation. But unfortunately, it is quickly deactivated by moisture. Here we report a Fe-doped Co3O4 spinel catalyst which demonstrates high activity and excellent moisture resistance for low temperature CO oxidation, especially at a low CO concentration of around 100 ppm which mimics the situations in automobile road tunnels and indoor parks.

Mesostructured Pd/Mn3O4 catalyst for efficient low-temperature CO oxidation especially under moisture condition

Mesostructured Mn3O4-supported Pd catalyst was successfully fabricated through a facile template-assisted pyrolysis and impregnation strategy. The resulting materials displayed large surface area and high dispersion of palladium species, and showed much enhanced catalytic activities for CO oxidation especially under moisture condition. For 2.7 wt% Pd-loaded catalyst, temperatures for 100% and 50% CO conversions were measured to be as low as 22 °C and 0 °C (4.0 vol% H2O), respectively. More importantly, the material showed excellent catalytic stability, and no activity loss was found even after the reaction for 30 hours. This unique catalytic durability under moisture condition was assigned to the synergetic effect between Pd nanoparticles and Mn3O4 support.

Alkali-assisted mild aqueous exfoliation for single-layered and structure-preserved graphitic carbon nitride nanosheets

Single-layered g-C3N4 nanosheets have been fabricated by delaminating directly its bulk counterpart in an alkaline solution. According to the theoretical modeling, the interaction of OH- with terminal NH2 or bridged NH group of the triazine units within bulk g-C3N4 crystal structure could result in decreased bonding energy between layers and promote the total delamination. The resulting g-C3N4 nanosheets colloid has a relatively high concentration (12g/L) compared with the traditional ultrasonic assistant exfoliation method. The delaminated nanosheets are revealed by atomic force microscopy to show a lateral size of a hundred nanometers and a thickness of about 0.4nm, which provides a direct evidence for the total exfoliation of g-C3N4 crystals into their single sheets. More importantly, the X-ray diffraction measurement confirms that the g-C3N4 nanosheets could be re-assembled with well-preserved original crystal structure. The exfoliation mechanism was also confirmed by the DFT calculation.

C, N co-doping promoted mesoporous Au/TiO2 catalyst for low temperature CO oxidation

Mesoporous C, N co-doped TiO2 was fabricated by a one pot pyrolysis method using ammonium titanyl oxalate as the precursor. When deposited with Au, the resulting materials possessed a relatively high surface area and highly dispersed gold nano-particles, exhibiting high catalytic activities for CO oxidation. The doping of C and N into meso-structured TiO2 increases the number of surface defect which could improve the absorption of oxygen, tune the metal-support interaction and promote the catalytic activities for CO oxidation.

One-pot pyrolytic synthesis of C–N-codoped mesoporous anatase TiO2 and its highly efficient photo-degradation properties

Polycrystalline mesoporous C–N-codoped anatase TiO2 has been successfully fabricated using a simple but efficient controlled thermal decomposition approach and their photo-degradation properties were evaluated. In such a synthesis, ammonium titanyl oxalate was first prepared and used as precursor. The C–N-codoped anatase TiO2 was then directly generated via the pyrolysis of the ammonium titanyl oxalate precursor and the resultant nano-sized crystallites connected together to form a mesoporous structure. The as-prepared material by calcination at 300 °C at a heating rate of 0.5 °C min−1 possessed a high surface area and showed extraordinarily high photocatalytic degradation properties under visible irradiation.

Mesoporous PdO/Pt/Al2O3 film produced by reverse-micro-emulsion and its application for methane micro-sensor

A simple, versatile and effective reverse micro-emulsion and pyrolysis protocol was presented for in situ growth of a PdO/Pt loaded mesoporous Al2O3 film. Noble metal (oxide) nanoparticles with a narrow size distribution were homogeneously dispersed throughout the Al2O3 support. Most importantly, the obtained worm-like catalyst network has both a high specific area and highly crystalline, which is favorable for application in methane catalytic combustion. When deposed on a micro-heater and used as a sensor element, the resulting micro-sensor demonstrated a short T90 response time, relatively high signal output, high enough signal/noise ratio and extraordinarily low power consumption for methane detection.

Facile synthesis of meso-structured Pd/FeOx and its highly catalytic performance for low temperature CO oxidation under ambient conditions

A series of meso-structured Pd/FeOx catalysts were successfully fabricated through a facile pyrolysis and in situ reduction strategy. The as-prepared materials possessed relatively high surface area and highly dispersed Pd species, and exhibited excellent low temperature CO oxidation properties under ambient conditions. Complete CO conversion could be achieved at as low as 0 °C, when 2.5 vol% H2O was introduced into the feed gas. In situ DRIFT analysis proved that these excellent catalytic properties can be attributed to the promotion of the water molecules and the synergetic effect between Pd nanoparticles and the meso-structured FeOx support.

Facile synthesis of nitrogen and sulfur dual-doped graphitized carbon microspheres and their high performance in the oxygen reduction reaction

A facile protocol for producing porous carbon spheres co-doped with nitrogen and sulfur is presented. Thiourea resorcinol-formaldehyde (RF) copolymerized resin microspheres were used as precursors. After only a simple calcination, the uniformly N, S co-doped graphitized carbon spheres could be obtained. Synergistic effects produced by the tunable content of N, S heteroatoms combined with the porous graphitized structures makes this one of the excellent non-platinum-based catalysts for the oxygen reduction reaction. When used in alkaline media, the materials exhibit high onset and half-wave potentials, high kinetic current density and a four-electron transfer pathway with low hydrogen peroxide yield, which is comparable to the commercial Pt/C catalyst. More importantly, the long-term durability test confirms its excellent stability for practical applications.

Design of a meso-structured Pd/NiO catalyst for highly efficient low temperature CO oxidation under ambient conditions

A meso-structured Pd/NiO catalyst was successfully fabricated through a controlled pyrolysis and in situ reduction protocol. The resulting material possessed a relatively high surface area and highly dispersed palladium species. It showed much higher catalytic activity and stability for CO oxidation under ambient conditions. Complete CO conversion could be achieved at as low as −20 °C, when 1.2 vol% H2O was introduced into the feed gas. The catalyst exhibited no detectable deactivation even after 100 hours of reaction. The extraordinary catalytic activity and durability were attributed to the promotion of the water molecules and the synergetic effect between the Pd nanoparticles and meso-structured NiO support.