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The photoactivity of methanol adsorbed on the anatase TiO2 (101) surface was studied by a combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculations. Isolated methanol molecules adsorbed at the anatase (101) surface show a negligible photoactivity. Two ways of methanol activation were found. First, methoxy groups formed by reaction of methanol with coadsorbed O2 molecules or terminal OH groups are photoactive, and they turn into formaldehyde upon UV illumination. The methoxy species show an unusual C 1s core-level shift of 1.4 eV compared to methanol; their chemical assignment was verified by DFT calculations with inclusion of final-state effects. The second way of methanol activation opens at methanol coverages above 0.5 monolayer (ML), and methyl formate is produced in this reaction pathway. The adsorption of methanol in the coverage regime from 0 to 2 ML is described in detail; it is key for understanding the photocatalytic behavior at high coverages. There, a hydrogen-bonding network is established in the adsorbed methanol layer, and consequently, methanol dissociation becomes energetically more favorable. DFT calculations show that dissociation of the methanol molecule is always the key requirement for hole transfer from the substrate to the adsorbed methanol. We show that the hydrogen-bonding network established in the methanol layer dramatically changes the kinetics of proton transfer during the photoreaction.

Formaldehyde (CH2O) adsorption on the anatase TiO2(101) surface was studied with a combination of experimental and theoretical methods. Scanning tunneling microscopy, noncontact atomic force microscopy, temperature-programmed desorption, and X-ray photoelectron spectroscopy were employed on the experimental side. Density functional theory was used to calculate formaldehyde adsorption configurations and energy barriers for transitions between them. At low coverages (<0.25 monolayer), CH2O binds via its oxygen atom to the surface 5-coordinated Ti atoms Ti5c (monodentate configuration). At higher coverages, many adsorption configurations with comparable adsorption energies coexist, including a bidentate configuration and paraformaldehyde chains. The adsorption energies of all possible adsorption configurations lie in the range from 0.6 to 0.8 eV. Upon annealing, all formaldehyde molecules desorb below room temperature; no other reaction products were detected.

This study reported a hierarchically ordered porous Ni-based cathode of a solid oxide electrolysis cell to realise stable CO 2 electrolysis without the need of safe gas. The Ni/(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 (YSZ) cathode support has a microchannel structure, which enabled efficient catalyst delivery to the reaction zone between the cathode and the electrolyte and resulted in facilitated gas diffusion through straight channels instead of the tortuous pores intrinsic to conventional porous electrodes. A catalyst network covering a Ni/YSZ scaffold reduced electrode polarisation resistance, prevented carbon formation and suppressed Ni oxidation. The facilitated gas diffusion diminished or eliminated concentration polarisation and carbon formation due to CO accumulation in the reaction zone. The novel hierarchical structure enables stable CO 2 electrolysis over conventional Ni-based cathodes with low capital and operational costs.

© 2017 Elsevier B.V. A novel dendritic microchanneled membrane has been prepared using a mesh-guided phase inversion process. A mesh-guided phase inversion mechanism is proposed to explain the formation mechanism of the microchannels. It is believed that the mesh influenced the formation of microchannels by restricting the organic solvent diffusion rate. The dendritic microchanneled structure was analysed using scanning electron microscopy and 3D reconstruction technologies. The microchanneled structure in this dendritic structure is found to be very different from the previously fabricated microchanneled membrane structure because the microchannels are formed by merging many small microchannels into larger channels with lateral dimensions corresponding to the mesh aperture size. It is confirmed that this structure offers a thin dense layer, a large surface area, good connectivity of microchannels and broad gas diffusion paths. As a result, the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d membrane with dendritic microchanneled structure demonstrates a very high oxygen permeation rate, 3.4 ml cm -2 min -1 at 900 °C.

The effects of calcination temperature on catalyst properties were studied on fibrous Ni/Al2O3 catalysts prepared by electrospinning, utilizing its high thermal and structural stability. The average Ni particle size was increased up to 27.1 nm as calcination temperature was increased from 700 to 1000 °C due to the increased NiAl2O4 crystal size, which also caused the higher reduction temperature required according to temperature-programmed reduction results and the lower catalytic activity in the dry reforming of methane. Interestingly, a higher reduction temperature resulted in more and uniform Ni particles instead of catalyst aggregation. It might be the reason that the high reduction temperature thermodynamically promoted Ni nucleation on the NiAl2O4 surface to initiate Ni precipitation from ceramic bulk. The catalytic activity in the dry reforming of methane confirms the reduction temperature effect.

Gas diffusion limitation within Ni/YSZ cathode supports of solid oxide electrolysis cells (SOECs) during steam electrolysis has been reported in previous studies. In this study, a microchanneled cathode support has been prepared by a mesh-templating phase-inversion process to improve the gas diffusion. Numerous channels with one end open on the cathode surface cross the support and are stopped on the other side of the support by a porous layer which acts as a cathode functional layer. The integrated structure is ideal for achieving both fast gas diffusion and a long three-phase-boundary for performing the cathode reactions. Compared with conventional cathode supports, the microchanneled cathode support produced higher current densities at low steam concentrations of feed gas during steam electrolysis, which is attributed to the fast gas diffusion achieved within the channels. Therefore, the microchannel structure of cathode supports can increase hydrogen yield and steam utilization efficiency.

Cathode-supported SOFCs are attractive for the potential utilization of hydrocarbons as fuels to generate electricity because Cu-based anodes can be used to deal with coke formation in the Ni-base anodes. However, Cu-based anodes cannot be used in anode-supported SOFCs because the high sintering temperatures (above 1350 °C) required for the formation of a dense electrolyte film may melt the Cu-based anodes. Compared with anode materials, cathode materials show higher sinterability, which leads to a low porosity of the supporting cathodes and in turn high gas diffusion resistance within the cathodes. To get around this problem, a novel supporting cathode with efficient gas diffusion channels will be developed in this study in order to achieve high performances in power generation.