Highly Dispersed NixGay Catalyst and La2O3 Promoter Supported by LDO Nanosheets for Dry Reforming of Methane: Synergetic Catalysis by Ni, Ga, and La2O3.

A highly active and stable Ni-based catalyst is the focal point for research on dry reforming of methane (DRM). Here, NixGay/La2O3-LDO catalysts composed of highly dispersed NixGay and La2O3 nanoparticles supported by the MgO/Al2O3 layered double oxide (LDO) nanosheets were synthesized by chemical methods. According to transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), CO2-TPD, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermal gravitational analysis (TGA), a synergistic reaction mechanism was proposed to explain the superior performance of the Ni0.8Ga0.2/La2O3-LDO catalyst. The NixGay alloy catalyst provides an effective way to balance the speed of CH4 cracking and CO2 disassociation, and the La2O3 promoter enriched the CO2 and ensured the generation of active O in time. They worked together to inhibit carbon accumulation and significantly improve the catalyst's activity and stability.

Fabrication of Opaline ZnO Photonic Crystal Film and Its Slow-Photon Effect on Photoreduction of Carbon Dioxide.

Monodisperse ZnO particles with adjustable size have been produced on a large scale by two-step seeding-growth polyol reactions. Through spin coating of supersaturated ZnO/diethylene glycol solution and evaporation of solvent, opaline ZnO photonic crystal (PC) film with good crystallinity and uniform photonic structures can be prepared from these ZnO particles. Compared with a disorderly stacked ZnO film, the ZnO PC film shows a higher activity in photocatalytic reduction of CO2 due to the generated slow photons at the edge of the photonic band gap and their promotion to the light absorption. When the electronic band gap of ZnO matches the red edge of the photonic band gap of ZnO PC, the enhancement factor of photocatalytic activity represented by CO evolution can be maximized to 2.64-fold in the current experiment. Compared to the traditional inverse opal photocatalysts, the opaline ZnO photocatalysts are prepared by simplified and scalable procedures, and they still possess the same enhancement in activity compared to ZnO without the photonic structure, which might be broadly used in solar energy utilization, environment protection, and many other green chemical processes in the future.

Core-Shell or Dimer Heterostructures? Synergistic Catalysis of an Advanced Oxidation Process at the Exposed Interface under Illumination.

Carbonaceous materials are biocompatible and ecofriendly catalysts for an advanced oxidation process (AOP) in the treatment of wastewater, but their activity is not satisfactory compared to that of the conventional metal and oxide catalysts. Here, dimer heterostructures of ZnO and Ni,N-codoped carbon (NiNC) are found to possess greatly improved activity in a photoassisted AOP reaction. In the synthesis of the composite of ZnO and ZIF-8, the adding sequence of Ni(NO3)2 and 2-methylimidazole can guide the formation of ZnO@NiZIF and ZnO-NiZIF particles, which are further converted to a core-shell particle of ZnO and NiNC (ZnO@NiNC) and a dimer particle of ZnO and NiNC (ZnO-NiNC) by calcination in N2. Although these two particles have many similar physicochemical properties, the ZnO-NiNC dimer particles show greatly enhanced activity for degradation of rhodamine B (RhB) under UV-vis illumination, where its reaction constant is 43 times of its own in the dark and 13 times higher than that of ZnO@NiNC under the same condition. A group of experiments reveal a synergistic mechanism for the ZnO-NiNC catalyst under illumination, in which the photoelectrons directionally migrate toward the exposed ZnO/NiNC interface and react with potassium peroxymonosulfate to produce more-reactive hydroxyl and persulfate radicals to accelerate the AOP reaction.

Synthesis of Magnetite-Semiconductor-Metal Trimer Nanoparticles through Functional Modular Assembly: A Magnetically Separable Photocatalyst with Photothermic Enhancement for Water Reduction.

Hybrid nanoparticles have intrinsic advantages to achieve better activity in photocatalysis compared to single-component materials, as it can synergistically combine functional components, which promote light absorption, charge transportation, surface reaction, and catalyst regeneration. Through functional modular assembly, a rational and stepwise approach has been developed to construct Fe3O4-CdS-Au trimer nanoparticles and its derivatives as magnetically separable catalysts for photothermo-catalytic hydrogen evolution from water. In a typical step-by-step synthetic process, Fe3O4-Ag dimers, Fe3O4-Ag2S dimers, Fe3O4-CdS dimers, and Fe3O4-CdS-Au trimers were synthesized by seeding growth, sulfuration, ion exchange, and in situ reduction consequently. Following the same reaction route, a series of derivative trimer nanoparticles with alternative semiconductor and metal were obtained for water-reduction reaction. The experimental results show that the semiconductor acts as an active component for photocatalysis, the metal nanoparticle acts as a cocatalyst for enhancement of charge separation, and the Fe3O4 component helps in the convenient separation of catalysts in magnetic field and improves photocatalytic activity under near-infrared illumination due to photothermic effect.