High-temperature solid oxide electrolysis cells (SOECs) are advanced electrochemical energy storage and conversion devices with high conversion/energy efficiencies. They offer attractive high-temperature co-electrolysis routes that reduce extra CO2 emissions, enable large-scale energy storage/conversion and facilitate the integration of renewable energies into the electric grid. Exciting new research has focused on CO2 electrochemical activation/conversion through a co-electrolysis process based on the assumption that difficult CO double bonds can be activated effectively through this electrochemical method. Based on existing investigations, this paper puts forth a comprehensive overview of recent and past developments in co-electrolysis with SOECs for CO2 conversion and utilization. Here, we discuss in detail the approaches of CO2 conversion, the developmental history, the basic principles, the economic feasibility of CO2/H2O co-electrolysis, and the diverse range of fuel electrodes as well as oxygen electrode materials. SOEC performance measurements, characterization and simulations are classified and presented in this paper. SOEC cell and stack designs, fabrications and scale-ups are also summarized and described. In particular, insights into CO2 electrochemical conversions, solid oxide cell material behaviors and degradation mechanisms are highlighted to obtain a better understanding of the high temperature electrolysis process in SOECs. Proposed research directions are also outlined to provide guidelines for future research.

A review of high temperature co-electrolysis of H2O and CO2 to produce sustainable fuels using solid oxide electrolysis cells (SOECs): advanced materials and technology

In perovskites, exsolution of transition metals has been proposed as a smart catalyst design for energy applications. Although there exist transition metals with superior catalytic activity, they are limited by their ability to exsolve under a reducing environment. When a doping element is present in the perovskite, it is often observed that the surface segregation of the doping element is changed by oxygen vacancies. However, the mechanism of co-segregation of doping element with oxygen vacancies is still an open question. Here we report trends in the exsolution of transition metal (Mn, Co, Ni and Fe) on the PrBaMn2O5+δ layered perovskite oxide related to the co-segregation energy. Transmission electron microscopic observations show that easily reducible cations (Mn, Co and Ni) are exsolved from the perovskite depending on the transition metal-perovskite reducibility. In addition, using density functional calculations we reveal that co-segregation of B-site dopant and oxygen vacancies plays a central role in the exsolution. Exsolution of transition metals from perovskites provides an effective route to useful catalysts, but the underlying factors governing exsolution remain poorly understood. Here, the authors find trends in exsolution in layered perovskites, showing that co-segregation of B-site dopant and oxygen vacancies plays a central role.

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Exsolution trends and co-segregation aspects of self-grown catalyst nanoparticles in perovskites.

The near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) have great potential in food industry and medical fields. For applications based on NIR spectroscopy, the next generation of...

Two-Site Occupation for Exploring Ultra-Broadband Near-Infrared Phosphor—Double-Perovskite La2MgZrO6:Cr3+

Solid oxide cell (SOC) based energy conversion systems have the potential to become the cleanest and most efficient systems for reversible conversion between electricity and chemical fuels due to their high efficiency, low emission, and excellent fuel flexibility. Broad implementation of this technology is however hindered by the lack of high-performance electrode materials. While many perovskite-based materials have shown remarkable promise as electrodes for SOCs, cation enrichment or segregation near the surface or interfaces is often observed, which greatly impacts not only electrode kinetics but also their durability and operational lifespan. Since the chemical and structural variations associated with surface enrichment or segregation are typically confined to the nanoscale, advanced experimental and computational tools are required to probe the detailed composition, structure, and nanostructure of these near-surface regions in real time with high spatial and temporal resolutions. In this review article, an overview of the recent progress made in this area is presented, highlighting the thermodynamic driving forces, kinetics, and various configurations of surface enrichment and segregation in several widely studied perovskite-based material systems. A profound understanding of the correlation between the surface nanostructure and the electro-catalytic activity and stability of the electrodes is then emphasized, which is vital to achieving the rational design of more efficient SOC electrode materials with excellent durability. Furthermore, the methodology and mechanistic understanding of the surface processes are applicable to other materials systems in a wide range of applications, including thermo-chemical photo-assisted splitting of H2O/CO2 and metal–air batteries.

Controlling cation segregation in perovskite-based electrodes for high electro-catalytic activity and durability

Perovskite oxides hold great promise as efficient electrocatalysts for various energy‐related applications owing to their low cost, flexible structure, and high intrinsic catalytic activity. However, conventional synthetic methods can only obtain perovskite catalysts with large particle sizes, small surface areas, and few morphological features, leading to limited catalytic activity and thus posing a major challenge toward real‐world applications. Reducing the size of bulk perovskites down to the nanosize represents an efficient way to improve the electrocatalytic performance. A comprehensive overview of recent progress in the nanostructuring of perovskites for catalyzing several key reactions in metal–air batteries, water splitting, and solid oxide fuel cells is provided. A range of synthetic protocols for making perovskite nanostructures are summarized, followed by an emphasis on how each method can be tailored to obtain high‐performing perovskite nanocatalysts. These recent advances highlight the enormous potential of nanosized perovskites for facilitating the electrocatalytic reactions. The remaining challenges and future directions are pointed out for the development of next‐generation perovskite‐based nanostructured catalysts.

Recent Advances in Novel Nanostructuring Methods of Perovskite Electrocatalysts for Energy-Related Applications

A metallic nanoparticle-decorated ceramic anode was prepared by in situ reduction of the perovskite Sr2FeMo0.65Ni0.35O6−δ (SFMNi) in H2 at 850 °C. The reduction converts the pure perovksite phase into mixed phases containing the Ruddlesden–Popper structure Sr3FeMoO7−δ, perovskite Sr(FeMo)O3−δ, and the FeNi3 bimetallic alloy nanoparticle catalyst. The electrochemical performance of the SFMNi ceramic anode is greatly enhanced by the in situ exsolved Fe–Ni alloy nanoparticle catalysts that are homogeneously distributed on the ceramic backbone surface. The maximum power densities of the La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolyte supported a single cell with SFMNi as the anode reached 590, 793, and 960 mW cm–2 in wet H2 at 750, 800, and 850 °C, respectively. The Sr2FeMo0.65Ni0.35O6−δ anode also shows excellent structural stability and good coking resistance in wet CH4. The prepared SFMNi material is a promising high-performance anode for solid oxide fuel cells.

High-Performance Anode Material Sr2FeMo0.65Ni0.35O6-δ with In Situ Exsolved Nanoparticle Catalyst.

A novel double perovskite Sr2FeMo2/3Mg1/3O6− δ is prepared and characterized as an anode material for solid oxide fuel cells (SOFCs). X-ray diffraction refinement reveals that Mg and Mo cations locate separately in two different B sites (B and B′ in A2BB′O6) while Fe occupies both B and B′ sites, forming the lattice structure with the form of Sr2(Mg1/3Fe2/3)(Mo2/3Fe1/3)O6−δ. The inactive element Mg doping not only endows the material with excellent redox structural stability but also triggers the creation of antisite defects in the crystal lattice, which provide the material with excellent electrochemical activity. The anode performance of Sr2FeMo2/3Mg1/3O6−δ is characterized in an La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolyte supported cell with La0.58Sr0.4Fe0.8Co0.2O3−δ cathode. A peak power density of 531, 803, 1038, and 1316 mW cm−2 at 750, 800, 850, and 900 °C, respectively, is achieved in humidified H2. The Sr2FeMo2/3Mg1/3O6−δ shows suitable thermal expansion coefficient (16.9(2) × 10−6 K−1), high electrical conductivity, and good tolerance to carbon deposition and sulfur poisoning. First-principle computations demonstrate that the presence of FeBOFeB′ bonds can promote the easy formation and fast migration of oxygen vacancies in the lattice, which are the key to affecting the anode reaction kinetics. The excellent overall performance of Sr2FeMo2/3Mg1/3O6−δ compound makes it a promising anode material for SOFCs.

Yan Li

Papers

High-Performance Anode Material Sr2FeMo0.65Ni0.35O6-δ with In Situ Exsolved Nanoparticle Catalyst.

Exceptionally High Performance Anode Material Based on Lattice Structure Decorated Double Perovskite Sr2FeMo2/3Mg1/3O6−δ for Solid Oxide Fuel Cells