Dehua Dong

Composite fuel electrode La0.2Sr0.8TiO3−δ–Ce0.8Sm0.2O2−δ for electrolysis of CO2 in an oxygen-ion conducting solid oxide electrolyser

Composite Ni-YSZ fuel electrodes are able to operate only under strongly reducing conditions for the electrolysis of CO(2) in oxygen-ion conducting solid oxide electrolysers. In an atmosphere without a flow of reducing gas (i.e., carbon monoxide), a composite fuel electrode based on redox-reversible La(0.2)Sr(0.8)TiO(3+δ) (LSTO) provides a promising alternative. The Ti(3+) was approximately 0.3% in the oxidized LSTO (La(0.2)Sr(0.8)TiO(3.1)), whereas the Ti(3+) reached approximately 8.0% in the reduced sample (La(0.2)Sr(0.8)TiO(3.06)). The strong adsorption of atmospheric oxygen in the form of superoxide ions led to the absence of Ti(3+) either on the surface of oxidized LSTO or the reduced sample. Reduced LSTO showed typical metallic behaviour from 50 to 700 °C in wet H(2); and the electrical conductivity of LSTO reached approximately 30 S cm(-1) at 700 °C. The dependence of [Ti(3+)] concentration in LSTO on P(O(2)) was correlated to the applied potentials when the electrolysis of CO(2) was performed with the LSTO composite electrode. The electrochemical reduction of La(0.2)Sr(0.8)TiO(3+δ) was the main process but was still present up to 2 V at 700 °C during the electrolysis of CO(2); however, the electrolysis of CO(2) at the fuel electrode became dominant at high applied voltages. The current efficiency was approximately 36% for the electrolysis of CO(2) at 700 °C and a 2 V applied potential.

Upgrading biomass-derived furans via acid-catalysis/hydrogenation: the remarkable difference between water and methanol as the solvent

In methanol 5-hydroxymethylfurfural (HMF) and furfuryl alcohol (FA) can be selectively converted into methyl levulinate via acid-catalysis, whereas in water polymerization dominates. The hydrogenation of HMF, furan and furfural with the exception of FA is much more selective in methanol than in water.

Eggshell membrane-templated synthesis of highly crystalline perovskite ceramics for solid oxide fuel cells

Highly crystalline perovskite ceramics were templated by an eggshell membrane (ESM) via strong metal-protein bonding. Templated Sm0.5Sr0.5CoO3 (SSC) ceramics retained an interwoven fibrous structure at a temperature up to 1000 °C. The use of citric acid-assisted sol–gel coating in the template synthesis greatly enhanced the crystallininty of the ceramic because the sol–gel process ensured the stoichiometric adsorption of ceramic precursors, and it also affected ceramic morphology. The highly crystalline SSC ceramic was used as a cathode material of solid oxide fuel cell (SOFC), and the cathode properties were compared with those prepared with the ceramic synthesized via a conventional combustion method. The maximum power density of the cell made with the templated SSC was 44.5% and 29.8% higher than that made with the combusted SSC at 600 °C and 500 °C, respectively, because the highly porous cathode constructed with the templated SSC reduced the cell concentration polarization and cathode polarization resistance. This study suggests high-performance perovskite ceramic for SOFC was produced via the template synthesis.

Microstructure control of oxygen permeation membranes with templated microchannels

Microchanneled ceramic membranes have been prepared by a templated phase-inversion process, and the effects of coagulant and slurry properties on the microchannel structure were investigated in order to control membrane microstructure for achieving highly-efficient oxygen permeation. Microchannels are formed by the rapid convection of coagulant and solvent during the phase-inversion, using a mesh as a template. The membrane microstructure is greatly affected by the method of applying coagulant, coagulant solubility and phase-inversion time. Polymer concentration and solid loading influence slurry viscosity, and long and uniform microchannels are formed from the slurries with low slurry viscosities. The membrane with long and uniform microchannels achieved high oxygen permeation fluxes because of short oxygen ion diffusion distances and large membrane surface area located within the numerous microchannels. The formation mechanism of the microstructure was also proposed on the basis of the experiment results.

A microchanneled ceramic membrane for highly efficient oxygen separation

A microchanneled ceramic membrane has been developed for oxygen separation. Numerous parallel microchannels traverse the ceramic membrane with one open end and another end terminating with a thin dense layer. Compared with conventional dense membranes, the new membrane substantially increases oxygen permeation flux by a factor of greater than 5.

Thermosetting polymer templated nanoporous sinter-active layer for low temperature solid oxide fuel cells

A facile synthesis method was developed to form a nanoporous metal oxide layer using poly(furfuryl alcohol) (PFA) as a thermosetting polymer template. A nanoporous Ce0.8Sm0.2O1.9 (SDC) layer with high sinterability was prepared on an anode-supported electrolyte film at 900 °C, and used as a sinter-active layer in cell fabrication to improve the interface between the inert electrolyte surface and the cathode layer of a solid oxide fuel cell (SOFC). The resulting saw-like interface improved the maximum powder density of the cell by 51% at 600 °C and 162% at 500 °C compared with that of the unmodified cell. The cell with the saw-like electrolyte–cathode interface exhibited lower electrode polarization resistance than those reported in the literature, and such improvement was much more significant at reduced operating temperatures (400–500 °C). Our study shows that the operating temperature of solid oxide fuel cells can be substantially lowered by simply improving the electrode–electrolyte interfaces.

Effects of water and alcohols on the polymerization of furan during its acid-catalyzed conversion into benzofuran

Furan, an important product from catalytic pyrolysis of biomass, has the potential to be further converted into value-added chemicals or biofuels. This study investigated the conversion of furan into benzofuran over a Bronsted acid catalyst (Amberlyst 70) at 140–190 °C in various solvents. With water as the solvent, furan could barely make its way to benzofuran as its polymerization dominated. With methanol as the solvent, the polymerization of furan was suppressed and benzofuran formation was enhanced substantially. This is because in methanol, the reactive intermediates (i.e., aldehydes) were stabilized and their involvement in polymerization reactions was suppressed. Other alcohols showed similar effects on suppressing polymerization. In dimethyl sulfoxide (DMSO), the polymerization of furan was also effectively suppressed. However, furan was not converted to benzofuran but to levulinic acid via a distinct reaction route.

Fibrous NiO/CeO2 nanocatalysts for the partial oxidation of methane at microsecond contact times

To maximize syngas yield by the catalytic partial oxidation of methane, fibrous NiO/CeO2 nanocatalysts were synthesized by a one-step template process for the catalytic reaction at microsecond contact times. High conversion performances at high gas hourly space velocities (∼107 h−1) indicate potential applications in gas conversion industry.

Hierarchically ordered porous Ni-based cathode-supported solid oxide electrolysis cells for stable CO2 electrolysis without safe gas

This study reported a hierarchically ordered porous Ni-based cathode of a solid oxide electrolysis cell to realise stable CO2 electrolysis without the need of safe gas. The Ni/(Y2O3)0.08(ZrO2)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 CO2 electrolysis over conventional Ni-based cathodes with low capital and operational costs.

Formation of nanoplate-based clew-like ZnO mesocrystals and their photocatalysis application

Clew-like ZnO mesocrystals comprised of ZnO nanoplates were created through a hydrothermal procedure in an aqueous solution using tartaric acid as the structure-directing additive. A detailed formation process of the nanoplate-based clew-like ZnO mesocrystal was investigated by varying reaction conditions especially the concentration of hexamethylenetetramine (HMT) and reaction time. It was found that the concentration of HMT played a significant role in the size distribution of ZnO products and the pileup degree of the nanoplates. Combined with the results obtained from the systematic time-dependent experiments, the formation of the nanoplate-based ZnO mesocrystal was mainly ascribed to the synergistic effect of the dipole moment generated among nanoplates and the electric field derived from a pre-formed inner core. The photocatalytic activity of samples synthesized using different HMT concentrations was also investigated. The results demonstrated that the adsorption percentage in the dark and degradation efficiency under UV-light irradiation were gradually improved with increasing the concentration of HMT. This was mainly ascribed to the increased specific surface area which promoted the migration of photon-generated carriers between the photocatalysts and rhodamine B (RhB) molecules.