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Ba 1− x Co 0.7 Fe 0.2 Nb 0.1 O 3− δ oxides ( x = 0, 0.05 and 0.10) were optimized as potential cathodes on oxygen ionic conductor electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). The creation of additional oxygen vacancies in Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ was confirmed. Low polarization resistances of 0.015, 0.029 and 0.089 Ω cm 2 were achieved at 700, 650 and 600 °C, respectively. By further optimizing the microstructure of the Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ electrode by using polyvinyl butyral as a pore former and adjusting the sintering temperature, the maximum power density was improved from 682 to 955 mW cm −2 at 650 °C. The operational stability of the Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ electrode was also investigated. The CO 2 in the surrounding air was detrimental to the oxygen reduction reaction; however, the performance of the cell was recovered after removing the CO 2 in the air at 650 or 700 °C. In addition, the Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ electrode in symmetrical cells exhibited a stable performance at 650 °C for 400 h and maintained a reliable performance after repeated thermal cycles from room temperature to 700 °C. The results showed that Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ was a promising cathode material for practical application in IT-SOFCs.

Sm0.5Sr0.5CoO3−δ (SSC)-impregnated cathodes are fabricated by the solution infiltration of metal nitrates. The effects of complexing agents on the phase structure and the effects of pore formers on the porosity of the scaffold are examined and optimized. The thermal expansion behavior, electrical conductivities and electrochemical performance of the cathodes are characterized and optimized. A pure perovskite phase is formed after heating at 800 °C by adding a relatively small quantity of glycine as the complexing agent. Polyvinyl butyral is selected as the pore former for the preparation of porous Sm0.2Ce0.8O1.9 (SDC) scaffolds. The thermal expansion coefficient increases slightly from 12.74 × 10−6 K−1 to 13.28 × 10−6 K−1 after infiltrating 20 wt% SSC into the SDC scaffold. The infiltrated cathode with 20 wt% SSC + 80 wt% SDC shows the electrical conductivity of 15 S cm−1 at 700 °C. A well-connected SSC network is formed in the cathode after infiltrating 20 wt% SSC into the SDC scaffold. Cathode polarization resistance values as low as 0.05 Ω cm2, peak power density values as high as 936 mW cm−2 and stable performance throughout 325 h of operation at 700 °C suggest that the cathodes with the 20 wt% SSC-infiltrated SDC are suitable for practical application. However, for the SSC infiltrated into the 8 mol% yttria-stabilized zirconia scaffold, the interfacial reaction continues to occur during the stability test at 700 °C. SDC is preferred as a scaffold for the infiltration of SSC to ensure long-term operational stability.

Co-free oxides with a nominal composition of LnBaFe2O5+δ, where Ln = La, Pr, Nd, Sm, Gd, and Y, were synthesized and phase structure, oxygen content, electronic conductivity, oxygen desorption, thermal expansion, microstructure and electrochemical performance were systematically investigated. Among the series of materials tested, LaBaFe2O5+δ oxide showed the largest electronic conductivity and YBaFe2O5+δ oxide had the smallest thermal expansion coefficient (TEC) of 14.6 × 10−6 K−1 within a temperature range of 200–900 °C. All LnBaFe2O5+δ oxides typically possess the TEC values smaller than 20 × 10−6 K−1. The oxygen content, electronic conductivity and TEC values are highly dependent on the cation size of the Ln3+ dopant. The lowest electrode polarization resistance in air under open circuit voltage condition was obtained for SmBaFe2O5+δ electrode and was approximately 0.043, 0.084, 0.196, 0.506 and 1.348 Ω cm2 at 800, 750, 700, 650 and 600 °C, respectively. The SmBaFe2O5+δ oxide also demonstrated the best performance after a cathodic polarization. A cell with a SmBaFe2O5+δ cathode delivered peak power densities of 1026, 748, 462, 276 and 148 mW cm−2 at 800, 750, 700, 650 and 600 °C, respectively. The results suggest that certain LnBaFe2O5+δ oxides have sufficient electrochemical performance to be promising candidates for cathodes in intermediate-temperature solid oxide fuel cells.

The influence of Co3O4 as a sintering aid for a series of cobalt-containing perovskite oxides on the microstructure and electrical properties have been investigated. X-ray diffraction and scanning electron microscopic results showed that well connected electrode particles with firm adhesion to the 8 mol% yttria-stabilized zirconia (YSZ) electrolyte surface were realized at a temperature free from interfacial phase reaction. Both ohmic and polarization resistances of symmetric cells by adopting YSZ electrolyte, measured by electrochemical impedance spectroscopy, were much lower than that without adding Co3O4. The peak power density of 1176 mW cm−2 at 750 °C was achieved when La0.6Sr0.4Co0.2Fe0.8O3−δ + Co3O4 was selected as a representative cobaltite cathode, which is much higher than a similar fuel cell with the cathode fabricated by a conventional way. Fabrication of interlayer-free electrodes by applying Co3O4 as a sintering aid is very simple and general, applicable for a wide range of cobalt-containing electrode materials.

The long-term stability for oxygen reduction reaction (ORR) of two typical perovskite cathode materials of SOFCs, i.e., Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) and Sm 0.5 Sr 0.5 CoO 3−δ (SSC), is investigated in a symmetric cell configuration under air condition at 700 °C using Sm 0.2 Ce 0.8 O 1.9 (SDC) electrolyte substrate and silver current collectors. Moreover, two different methods of silver current collection are tested, i.e., whole electrode surface deposited with a diluted silver paste (CC-01) and a mesh-like current collector using concentrated silver paste (CC-02). Electrochemical impedance spectra are applied for stability investigations. With the CC-01 current collector, the performance of the electrode deteriorates significantly, although the initial performance is good. By contrast, fairly stable performance is obtained from symmetric cells with either BSCF or SSC + SDC electrodes using the CC-02 current collector, even though a phase transition is observed for BSCF. For instance, after approximately 800 h of continuous stability testing, the area-specific resistance of the BSCF electrode retains a value of approximately 0.065 Ω cm 2 , except for a slight fluctuation within the range of 0.06–0.07 Ω cm 2 . These findings reveal that both BSCF and SSC can be stably operated for ORR under symmetric cell conditions; however, an appropriate current collection method is crucial to achieving stable performance.

A series of ultrastable Y (USY) zeolite samples with different acidities and pore sizes are prepared via hydrothermal and acid treatments. NiW sulfide catalysts are maintained on a mixed support of USY zeolite and Al 2 O 3 . The catalytic coupled hydrogenation and ring-opening performance are studied on a continuous fixed-bed reactor using tetralin as the model compound. All catalysts show high tetralin conversions under the reaction conditions studied [ T = 613 K, P = 4.0 MPa, LHSV = 2.0 h −1 , H 2 /oil (v/v) = 500]. Product yields and selectivity are mainly determined by the zeolite property (i.e., acidity). A medium to strong zeolite acidity is the key factor in the ring-opening selectivity of tetralin. A maximum high cetane ring-opening product yield of 39.1 wt% is obtained at a C 10 yield of 98.2 wt% for a USY zeolite with medium acidity. Using an fluid catalytic cracking light cycle oil feedstock, the activity of the catalyst is higher than that of commercial catalysts, giving a 14-unit cetane number increase at a diesel yield of 97.6 wt%. Because the first step of the ring-opening reaction is hydrogenation, the catalyst must have high hydrogenation activity. The WS 2 slabs have a high average layer number of 2.7 on the catalyst using the support presented here.

The effect of Si/Al ratio of the starting NaY on hydro-upgrading catalyst performance for LCO was studied. Y type zeolite modified from higher Si/Al ratio of the starting NaY also had higher framework Si/Al ratio. Three catalysts of W-Ni supported on different modified Y type zeolites and Al 2 O 3 were prepared by impregnation method. The catalysts were characterized by XRD, BET, DRS and HRTEM, and evaluated with a micro-reactor using tetralin as a model compound and a 100 ml hydrogenation test unit using FCC LCO as feedstocks. By contrast, tungsten supported on Y type zeolite modified from higher Si/Al ratio of the starting NaY zeolite had more type II active phase and WS 2 is highly stacked, exhibiting the weak interaction with Al 2 O 3 and should have higher activity. The revaluation results revealed that the catalyst prepared by higher Si/Al ratio of the starting NaY zeolite has higher tetralin conversion and better hydro-upgrading performance for FCC LCO.

A novel hydrotreating (HT) catalyst of Mo—W—Ni—P supported on γ-Al 2 O 3 modified by a Group IVA element and a hydroisomerizing (HI) catalyst of W-Ni supported on modified zeolite β with mesopores were prepared by the impregnation method. An integrated process using HT and HI catalysts was designed, and its advantages were well-investigated for directly producing clean diesel from various feedstocks. An industrial application shows that the integrated catalysts have flexible operating modes and are suitable for a wide range of feedstocks. For the HT operating mode, the integrated catalysts showed better hydrodesulfurization (HDS) performance for upgrading the poor quality diesel with a sulfur content of 1000 ppmw and a nitrogen content of 1131 ppmw. The sulfur content of diesel product is less than 40 ppmw, coupled with a hydrodenitrogenation (HDN) rate of 85.76% and an HDS rate of 96.3%. The cetane index increases by 7 units, and the diesel yield is more than 98.0 wt %. For the hydro-dewaxing operating mode, the integrated catalysts showed excellent catalytic performance for upgrading the feeds, with a sulfur content of 990 ppmw and a nitrogen content of 805 ppmw. The HDN rate of 99.42 % and HDS rate of99.99% were also achieved. More importantly, while retaining the cetane index, the diesel yield was as high as 88.72 wt % and the sulfur content and solidifying point of diesel were less than 10 ppmw and -29.3 °C, respectively. The higher HDS and HDN activities of the integrated catalysts are associated primarily with enhanced hydrogenation activity and increased acidity of the HI catalyst.

Two Ni/W hydrodearomatization (HDA) catalysts, CAT-1 and CAT-2, were prepared by wetness impregnation on mixed supports of USY zeolite and amorphous silica−alumina. The structure and properties of CAT-1 and CAT-2 catalysts were characterized by XRD, XRF, pyridine-IR, and N2 adsorption/desorption techniques. The hydrotreating tests with a lower initial boiling point light cycle oil from fluid catalytic cracking showed that CAT-1 catalyst achieved hydrodearomatization, hydrodesulfurization (HDS), and hydrodenitrogenation (HDN) performance: 97.4% hydrodesulfurization, 99.5% hydrodenitrogenation, 14 cetane number improvement, 97.6 wt % diesel yield, and 0.0410 g/cm3 density reduction. The high HDA activity of CAT-1 catalyst was attributed to a low total acidity and Lewis acidity. Adding various modified zeolites did not significantly influence HDS and HDN activities and diesel yield.