Solid oxide electrolysis: Concluding remarks

Renewable energy resources such as solar energy, wind energy, hydropower or geothermal energy have attracted significant attention in recent years. Renewable energy sources have to match supply with demand, therefore it is essential that energy storage devices (e.g., secondary batteries) are developed. However, secondary batteries are accompanied with critical problems such as high cost for the limited energy storage capacity and loss of charge over time. Energy storage in the form of chemical species, such as H-2 or CO2, have no constraints on energy storage capacity and will also be essential. When plentiful renewable energy exists, for example, it could be used to convert H2O into hydrogen via water electrolysis. Also, renewable energy resources could be used to reduce CO2 into CO and recycle CO2 and H2O into sustainable hydrocarbon fuels in solid oxide electrolysis (SOE).open0

Efficient CO2 Utilization via a Hybrid Na-CO2 System Based on CO2 Dissolution

Carbon capture, utilization, and sequestration technologies have been extensively studied to utilize carbon dioxide (CO2), a greenhouse gas, as a resource. So far, however, effective technologies have not been proposed owing to the low efficiency conversion rate and high energy requirements. Here, we present a hybrid Na-CO2 cell that can continuously produce electrical energy and hydrogen through efficient CO2 conversion with stable operation for over 1,000 hr from spontaneous CO2 dissolution in aqueous solution. In addition, this system has the advantage of not regenerating CO2 during charging process, unlike aprotic metal-CO2 cells. This system could serve as a novel CO2 utilization technology and high-value-added electrical energy and hydrogen production device

SOFC Anodes Based on Infiltration of La\u3csub\u3e0.3\u3c/sub\u3eSr\u3csub\u3e0.7\u3c/sub\u3eTiO\u3csub\u3e3\u3c/sub\u3e

Composites formed by infiltration of 45 wt % La0.3Sr0.7TiO3 (LST) into 65% porous yttria-stabilized zirconia (YSZ) were examined for application as solid oxide fuel cell (SOFC) anodes. Although LST does not react with YSZ, the structure of the LST deposits was strongly affected by the calcination temperature. At 1373 K, the LST formed loosely packed, 0.1 µm particles that filled the YSZ pores. The conductivity of this composite depended strongly on the pretreatment conditions but was greater than 0.4 S/cm after heating to 1173 K in humidified (3% H2O)H2. Following calcination at 1573 K, the LST had sintered significantly, decreasing the conductivity of the composite by a factor of approximately 5. The addition of a catalyst was critical for achieving reasonable electrochemical performance, with the addition of 0.5 wt % Pd and 5 wt % ceria increasing the power density of otherwise identical cells from less than 20 to 780 mW/cm2 for operation in humidified (3% H2O)H2 at 1073 K. Electrodes prepared from LST deposits calcined at 1373 K were found to exhibit a much better performance than those prepared from LST deposits calcined at 1573 K, demonstrating that the structure of the composite is critical for achieving high performance

A Bifunctional Hybrid Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions: Nano-Co3O4-Deposited La0.5Sr0.5MnO3 via Infiltration

For rechargeable metal-air batteries, which are a promising energy storage device for renewable and sustainable energy technologies, the development of cost-effective electrocatalysts with effective bifunctional activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been a challenging task. To realize highly effective ORR and OER electrocatalysts, we present a hybrid catalyst, Co3O4-infiltrated La0.5Sr0.5MnO3-delta (LSM@Co3O4), synthesized using an electrospray and infiltration technique. This study expands the scope of the infiltration technique by depositing similar to 18 nm nanoparticles on unprecedented similar to 70 nm nano-scaffolds. The hybrid LSM@Co3O4 catalyst exhibits high catalytic activities for both ORR and OER (similar to 7 times, similar to 1.5 times, and similar to 1.6 times higher than LSM, Co3O4, and IrO2, respectively) in terms of onset potential and limiting current density. Moreover, with the LSM@Co3O4, the number of electrons transferred reaches four, indicating that the catalyst is effective in the reduction reaction of O-2 via a direct four-electron pathway. The study demonstrates that hybrid catalysts are a promising approach for oxygen electrocatalysts for renewable and sustainable energy devices

Scandium Doping Effect on a Layered Perovskite Cathode for Low-Temperature Solid Oxide Fuel Cells (LT-SOFCs)

Layered perovskite oxides are considered as promising cathode materials for the solid oxide fuel cell (SOFC) due to their high electronic/ionic conductivity and fast oxygen kinetics at low temperature. Many researchers have focused on further improving the electrochemical performance of the layered perovskite material by doping various metal ions into the B-site. Herein, we report that Sc3+ doping into the layered perovskite material, PrBaCo2O5+ (PBCO), shows a positive effect of increasing electrochemical performances. We confirmed that Sc3+ doping could provide a favorable crystalline structure of layered perovskite for oxygen ion transfer in the lattice with improved Gold-schmidt tolerance factor and specific free volume. Consequently, the Sc3+ doped PBCO exhibits a maximum power density of 0.73 W cm(-2) at 500 degrees C, 1.3 times higher than that of PBCO. These results indicate that Sc3+ doping could effectively improve the electrochemical properties of the layered perovskite material, PBCO

SOFC Anodes Based on LST–YSZ Composites and on Y\u3csub\u3e0.04\u3c/sub\u3eCe\u3csub\u3e0.48\u3c/sub\u3eZrM\u3csub\u3e0.48\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e

The properties of solid oxide fuel cell (SOFC) anode functional layers prepared by impregnation of 1 wt % Pd and 10 wt % ceria into porous scaffolds of either Y0.04Ce0.48Zr0.48O2 (CZY) or composites of La0.3Sr0.7TiO3 (LST) and yttria-stabilized zirconia (YSZ) were examined to determine whether these scaffold materials would have sufficient electronic and ionic conductivity. Laminated tapes were cofired to produce 50 m YSZ electrolytes and 50 µm scaffolds, supported on LSF–YSZ cathodes. The electronic conductivities of LST–YSZ composites were a function of the porosity and the weight fraction of LST but could be sufficient for use in thin functional layers. However, anodes made with LST–YSZ composites had higher nonohmic losses than cells made with YSZ scaffolds. With CZY scaffolds, some migration of Ce into the YSZ electrolyte was observed after cofiring. While CZY exhibited electronic conductivity, the loss in ionic conductivity compared to YSZ again resulted in higher nonohmic losses. The implications of these results for producing better ceramic anodes are discussed

Electrochemical performance of YST infiltrated and fe doped YST infiltrated YSZ anodes for IT-SOFC

Donor doped and donor-acceptor co-doped strontium titanate perovskite are investigated for intermediate temperature solid oxide fuel cells (IT-SOFCs) anodes. Y0.08Sr0.88TiO3-delta and Y0.08Sr0.92Ti1-xFexO3-delta (x = 0.2, 0.4) anodes were prepared by infiltration in 65% porous yttria stabilized zirconia (YSZ) scaffolds. The microstructure and electrical conductivity of Y0.08Sr0.88TiO3-delta and Y0.08Sr0.92Ti1-xFexO3-delta strongly depends on Fe content. The conductivity of Y0.08Sr0.88TiO3-delta andY(0.08)Sr(0.92)Ti(1-x)Fe(x)O(3-delta); decreases with increasing Fe content in humidified H-2. Y0.08Sr0.88TiO3-delta, Y0.08Sr0.92Ti0.8Fe0.2O3-delta, and Y0.08Sr0.92Ti0.6Fe0.4O3-delta, anodes with a Pd/CeO2 catalyst show peak power density of 298, 421, and 321 mW cm(-2), respectively, in wet H-2 at 1073 K.open0

Review on exsolution and its driving forces in perovskites

Exsolution is a promising method to design metal nanoparticles for electrocatalysis and renewable energy. Metal nanoparticles exsolved from perovskite oxide lattices have been utilized as catalysts in many energy fields because of their high durability and excellent electro-catalytic properties. Although this method has received much attention in recent years, a comprehensive understanding is still lacking because of difficulties in finding a rational combination of driving forces and perovskite supports. Thus, the aim of our work here is to recapitulate the principles of exsolution and collect various exsolution studies by categorizing the driving forces of exsolution and the structural characteristics of perovskite supports. These classifications provide guidelines for selecting suitable materials groups and remodeling existing materials, thereby exploring applications of catalysts using exsolution that are applicable to academic and industrial fields

Fe@N-Graphene Nanoplatelet-Embedded Carbon Nanofibers as Efficient Electrocatalysts for Oxygen Reduction Reaction

An activated carbon nanofiber (CNF) is prepared with incorporated Fe-N-doped graphene nanoplatelets (Fe@NGnPs), via a novel and simple synthesis approach. The activated CNF-Fe@NGnP catalysts exhibit substantially improved activity for the oxygen reduction reaction compared to those of commercial carbon blacks and Pt/carbon catalysts.clos

Precise Modulation of Triple-Phase Boundaries towards a Highly Functional Exsolved Catalyst for Dry Reforming of Methane under a Dilution-Free System

Dry reforming of methane (DRM) has been emerging as a viable solution to achieving carbon neutrality enhanced by the Paris Agreement as it converts the greenhouse gases of CO2 and CH4 into industrially useful syngas. However, there have been limited studies on the DRM catalyst under mild operating conditions with a high dilution gas ratio due to their deactivation from carbon coking and metal sintering. Herein, we apply the triple-phase boundary (TPB) concept to DRM catalyst via exsolution phenomenon that can secure elongated TPB by controlling the Fe-doping ratio in perovskite oxide. Remarkably, the exsolved catalyst with prolongated TPB shows exceptional CO2 and CH4 conversion rates of 95.9 % and 91.6 %, respectively, stable for 1000 hours under a dilution-free system. DFT calculations confirm that the Lewis acid of support and Lewis base of metal at the TPB promote the adsorption of reactants, resulting in lowering the overall CO2 dissociation and CH4 dehydrogenation energy