Guoheng Yin

Direct synthesis of ethanol via CO2 hydrogenation using supported gold catalysts

An efficient titania supported Au nanocluster (NC) has been prepared for the direct synthesis of useful EtOH from CO2 and H2. The unique creation of an excellent synergistic effect between Au NCs and the underlying TiO2 support, especially the anatase crystal phase with abundant oxygen vacancies, can achieve the high performance for EtOH synthesis under moderate and practical conditions.

Ti3+-Promoted High Oxygen-Reduction Activity of Pd Nanodots Supported by Black Titania Nanobelts

One-dimensional nanocrystals favoring efficient charge transfer have attracted enormous attentions, and conductive nanobelts of black titania with a unique band structure and high electrical conductivity would be interestingly used in electrocatalysis. Here, Pd nanodots supported by two kinds of black titania, the oxygen-deficient titania (TiO2-x) and nitrogen-doped titania (TiO2-x:N), were synthesized as efficient composite catalysts for oxygen-reduction reaction (ORR). These composite catalysts show improved catalytic activity with lower overpotential and higher limited current, compared to the Pd nanodots supported on the white titania (Pd/TiO2). The improved activity is attributed to the relatively high conductivity of black titania nanobelts for efficient charge transfer (CT) between Ti3+ species and Pd nanodots. The CT process enhances the strong metal-support interaction (SMSI) between Pd and TiO2, which lowers the absorption energy of O2 on Pd and makes it more suitable for oxygen reduction. Because of the stronger interaction between Pd and support, the Pd/TiO2-x:N also shows excellent durability and immunity to methanol poisoning.

Efficient Conversion of CO2 to Methane Photocatalyzed by Conductive Black Titania

One of the major challenges encountered in CO2 utilization is the development of available and cost‐efficient catalysts with sufficient activity, selectivity, and stability for the generation of useful methane. Here, conductive black titania, TiO2−x, is found to be efficient in photocatalyzing the reduction of CO2 to CH4. This unique material comprises a crystalline core–amorphous shell structure (TiO2@TiO2−x) with numerous surface oxygen vacancies, which facilitates the adsorption and chemical activation of CO2 molecules. Under full solar irradiation, the optimized 500‐TiO2−x material with narrowed band gap and intermediate states below the conduction band tail exhibits a high space‐time yield of CH4 of 14.3 μmol g−1 h−1, with 74 % selectivity and excellent photostability. The present findings can make a significant contribution, not only to develop the surface electron‐modified black TiO2 catalyst to boost photocatalytic efficiency, but also to establish a really viable and convenient CH4 production process for CO2 conversion and renewable solar energy storage.

Efficient Reduction of CO2 to CO Using Cobalt–Cobalt Oxide Core–Shell Catalysts

The route of converting CO2 to CO by reverse water-gas shift (RWGS) reaction is of particular interest due to the direct use of CO as feedstock in many significant industrial processes. Here, an engineered cobalt-cobalt oxide core-shell catalyst (Co@CoO) with nanochains structure has been made for the efficient reduction of CO2 to useful CO. Owing to the excellent performance for H2 activation of metal nanoparticles and the enhanced absorption and activation for CO2 molecule of defective metal oxides, the unique synergistic effect of metallic Co and encapsulating coordinatively unsaturated CoO species shows high performance for clean generation of CO under moderate and practical conditions. Furthermore, with N-dopant into the defective CoO shell, the Co@CoO-N achieves the highest conversion of 19.2 % and an exceptional CO evolution rate of 96 mL min-1  gcat-1 at 523 K with a gas hourly space velocity (GHSV) of 42,000 mL gcat-1  h-1 , which is comparable with the previously reported materials under identical conditions.

Prominent Electron Penetration through Ultrathin Graphene Layer from FeNi Alloy for Efficient Reduction of CO2 to CO

The chemical transformation of CO2 is an efficient approach in low-carbon energy system. The development of nonprecious metal catalysts with sufficient activity, selectivity, and stability for the generation of CO by CO2 reduction under mild conditions remains a major challenge. A hierarchical architecture catalyst composed of ultrathin graphene shells (2-4 layers) encapsulating homogeneous FeNi alloy nanoparticles shows enhance catalytic performance. Electron transfer from the encapsulated alloy can extend from the inner to the outer shell, resulting in an increased charge density on graphene. Nitrogen atom dopants can synergistically increase the electron density on the catalyst surface and modulate the adsorption capability for acidic CO2 molecules. The optimized FeNi3 @NG (NG=N-doped graphene) catalyst, with significant electron penetration through the graphene layer, effects exceptional CO2 conversion of 20.2 % with a CO selectivity of nearly 100 %, as well as excellent thermal stability at 523 K.

Efficient Photocatalytic Reduction of CO2 Using Carbon-Doped Amorphous Titanium Oxide

CO2‐related solar to chemical conversions have gained extensive interest due to the great concerns on renewable energy utilization. Here, we have demonstrated a new synthetic route to C‐doped amorphous titanium oxide using a facile citric acid assisted sol‐gel method for efficient photocatalytic reduction of CO2. The synthesized amorphous material exhibits a mesoporous structure with high specific surface area and a significantly narrowed band gap of 2.1 eV, which are crucial for solar light harvesting and adsorption/chemical activation of CO2 for energy transformation. The amorphization, mesoporous structure, and the band structure of the C‐doped samples were also successfully tuned by controlling the annealing temperatures. The optimized catalyst annealed at 300 °C shows the highest specific surface area, favorable visible‐light response as well as the considerable performance for CO2 photoreduction. Moreover, the further treatment of Al reduction can induce numerous surface oxygen vacancies on the amorphous sample and thus efficiently restrain the recombination of photogenerated carriers. Of significant importance is that the Al‐reduced catalyst achieves excellent performance with the space‐time yield of CH4 and CO of 4.1 and 2.5 μmol g−1 h−1 for solar light, and 0.53 and 0.63 μmol g−1 h−1 for visible light, respectively. This sample is also stable for photocatalytic CO2 transformation.