Jingyun Ye

Progresses in the Preparation of Coke Resistant Ni‐based Catalyst for Steam and CO2 Reforming of Methane

Steam reforming of methane is an extremely important process for the hydrogen and syngas production. Nickel‐based catalysts have been extensively employed in the industrial process of steam reforming because of their high activity, low cost, and the plentiful supply of Nickel. Nickel‐based catalysts have also shown high activity for CO2 reforming of methane, which has been considered as a good option, with consumption of a significant amount of carbon dioxide. However, a major challenge is that Ni catalysts have a high thermodynamic potential for coke formation during reforming reactions. For steam reforming, coke formation induces deactivation of the catalyst, especially if the carbon forms as carbon filaments. The filamentous carbon material has a high mechanical strength and can cause mechanical deformation of the catalyst. For CO2 reforming, coke formation over Ni catalyst is even more serious and leads to rapid deactivation of the catalyst. It is highly desired to design and synthesize a coke resistant Ni catalyst not only for reforming of methane, but also for reforming of other hydrocarbons (including biomass derived hydrocarbons). Herein we summarize the very recent progresses in the design, synthesis, and characterization of coke resistant Ni catalysts for steam and CO2 reforming of methane. The progresses in the use of promoters, in the effect of supporting materials and in the preparation methods have been discussed. The thermal stability, regeneration, and future development of coke resistant Ni catalysts for these processes are also briefly addressed.

Tunability of Band Gaps in Metal–Organic Frameworks

The tunability of the band gaps in Zn-based metal-organic frameworks (MOFs) has been experimentally demonstrated via two different approaches: changing the cluster size of the secondary building unit (SBU) or alternating the conjugation of the organic linker.

A DFT study of methanol dehydrogenation on the PdIn(110) surface.

Methanol decomposition to CO and H(2) on PdIn(110) has been studied by following the sequential dehydrogenation steps from CH(3)OH → CH(3)O → CH(2)O → CHO → CO using density functional theory slab calculations. The first three of the four elementary steps are strongly endothermic. The last step, i.e., CHO → CO + H, is almost thermal neutral. We also examined the effect of considering van der Waals interaction on the reaction energy and activation barrier of each elementary step by using the optB88-vdW and optB86b-vdW functionals. Our results show that both overall reaction energy and activation barrier were reduced by including van der Waals interactions but the qualitative picture remains unchanged.

Acetone-Assisted Oxygen Vacancy Diffusion on TiO2(110)

We have studied the dynamic relationship between acetone and bridge-bonded oxygen (Ob) vacancy (VO) defect sites on the TiO2(110)-1 × 1 surface using scanning tunneling microscopy (STM) and density function theory (DFT) calculations. We report an adsorbate-assisted VO diffusion mechanism. The STM images taken at 300 K show that acetone preferably adsorbs on the VO site and is mobile. The sequential isothermal STM images directly show that the mobile acetone effectively migrates the position of VO by a combination of two acetone diffusion channels: one is the diffusion along the Ob row and moving as an alkyl group, which heals the initial VO; another is the diffusion from the Ob row to the five-coordinated Ti(4+) row and then moving along the Ti(4+) row as an acetone, which leaves a VO behind. The calculated acetone diffusion barriers for the two channels are comparable and agree with experimental results.

Imaging reactions of acetone with oxygen adatoms on partially oxidized TiO2(110)

Understanding the interaction of O2 with ketones on metal oxide surfaces is important for the photo-oxidation of toxic organic molecules. The consecutive reaction steps of acetone molecules with oxygen adatoms (Oas) on partially oxidized TiO2(110) surfaces have been studied using high-resolution scanning tunneling microscopy (STM) at 300 K. The sequential isothermal STM images reveal two types of acetone-Oa species as a result of reactions of acetone with an oxygen adatom and a bridging bound oxygen vacancy (V(O)). One such species is the Ti5c-bound acetone-Oa diolate formed from Ti5c-bound acetone reacting with Oa. The diolate is mobile at 300 K and can assist the diffusion of surface Oa by exchanging the acetone oxygen with the Oa. The second acetone-Oa species is the V(O)-bound acetone-Oa complex formed from a V(O)-bound acetone reacting with an Oa located on the neighboring Ti row. The V(O)-bound complex is stationary at 300 K. This species has not been reported previously.