Oxygen electrocatalysis, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), plays an extremely important role in oxygen‐based renewable‐energy technologies such as ...rechargeable metal‐air batteries, regenerative fuel cells and water splitting. Perovskite oxides have recently attracted increasing interest and hold great promise as efficient ORR and OER catalysts to replace noble‐metal‐based catalysts, owing to their high intrinsic catalytic activity, abundant variety, low cost, and rich resources. The introduction of perovskite‐carbon interfaces by forming perovskite/carbon composites may bring a synergistic effect between the two phases, thus benefiting the oxygen electrocatalysis. This review provides a comprehensive overview of recent advances in perovskite/carbon composites for oxygen electrocatalysis in alkaline media, aiming to provide insights into the key parameters that influence the ORR/OER performance of the composites, including the physical/chemical properties and morphologies of the perovskites, the multiple roles of carbon, the synthetic method and the synergistic effect. A special emphasis is placed on the origin of the synergistic effect associated with the interfacial interaction between the perovskite and the carbon phases for enhanced ORR/OER performance. Finally, the existing challenges and the future directions for the synthesis and development of more efficient oxygen catalysts based on perovskite/carbon composites are proposed.
A comprehensive review of recent developments of perovskite/carbon composites for oxygen electrocatalysis in alkaline media is provided, aiming to offer insights into key parameters that influence the ORR/OER performance and the origin of synergistic effect associated with the interfacial interaction in the composites. The existing challenges and future perspectives are also presented.
Efficient electrocatalysts for hydrogen evolution reaction are key to realize clean hydrogen production through water splitting. As an important family of functional materials, transition metal ...oxides are generally believed inactive towards hydrogen evolution reaction, although many of them show high activity for oxygen evolution reaction. Here we report the remarkable electrocatalytic activity for hydrogen evolution reaction of a layered metal oxide, Ruddlesden-Popper-type Sr
RuO
with alternative perovskite layer and rock-salt SrO layer, in an alkaline solution, which is comparable to those of the best electrocatalysts ever reported. By theoretical calculations, such excellent activity is attributed mainly to an unusual synergistic effect in the layered structure, whereby the (001) SrO-terminated surface cleaved in rock-salt layer facilitates a barrier-free water dissociation while the active apical oxygen site in perovskite layer promotes favorable hydrogen adsorption and evolution. Moreover, the activity of such layered oxide can be further improved by electrochemistry-induced activation.
Development of cost-effective and efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of prime importance to emerging renewable energy technologies. ...Here, we report a simple and effective strategy for enhancing ORR and OER electrocatalytic activity in alkaline solution by introducing A-site cation deficiency in LaFeO3 perovskite; the enhancement effect is more pronounced for the OER than the ORR. Among the A-site cation deficient perovskites studied, La0.95FeO3‑δ (L0.95F) demonstrates the highest ORR and OER activity and, hence, the best bifunctionality. The dramatic enhancement is attributed to the creation of surface oxygen vacancies and a small amount of Fe4+ species. This work highlights the importance of tuning cation deficiency in perovskites as an effective strategy for enhancing ORR and OER activity for applications in various oxygen-based energy storage and conversion processes.
The development of clean and efficient energy conversion and storage systems is becoming increasingly vital as a result of accelerated global energy consumption. Solid oxide fuel cells (SOFCs) as one ...key class of fuel cells have attracted much attention, owing to their high energy conversion efficiency and low emissions. However, some serious problems appeared because of the scorching operating temperatures of SOFCs (800–1000 °C), such as poor thermomechanical stability and difficult sealing, resulting in a short lifespan and high cost of SOFCs. Therefore, lowering the operating temperature of SOFCs to mid-range and even low range has become one of the main goals for SOFC development in the recent years. Looking for new cathode materials with high electrocatalytic activity and robust stability at relatively low temperatures is one of the essential requirements for intermediate-to-low-temperature SOFCs (ILT-SOFCs). During the past 15 years, we put considerable efforts into the development of alternative cathode materials for ILT-SOFCs. In this review, we give a summary of our progress from such efforts. We first summarize several strategies that have been adopted for developing cathode materials with high activity and durability toward reducing operating temperatures of SOFCs. Then, our new ideas and progress on cathode development with respect to activity and stability are provided. Both the cathodes of oxygen-ion-conducting SOFCs and protonic-conducting SOFCs are discussed. In the end, we outline the opportunities, challenges, and future approaches for the development of cathodes for ILT-SOFCs.
Overcoming the sluggish activity of cathode materials is critical to realizing the wide‐spread application of intermediate‐temperature solid oxide fuel cells. Herein, a new way is reported to tune ...the performance of perovskite‐type materials as oxygen reduction electrodes by embedding anions (F−) in oxygen sites. The obtained perovskite oxyfluorides SrFeO3−σ−δFσ and SrFe0.9Ti0.1O3−σ−δFσ (σ = 0.05 and 0.10) show improved electrocatalytic activity compared to their parent oxides, achieving area specific resistance values of 0.875, 0.393, and 0.491 Ω cm2 for SrFeO3−δ, SrFeO2.95−δF0.05, and SrFeO2.90−δF0.10, respectively, at 600 °C in air. Such improved performance is a result of the improved bulk diffusion and surface exchange properties due to anion doping. Moreover, favorable stability in performance is also demonstrated for the F− anion‐doped perovskites as oxygen reduction electrodes at 650 °C for a test period of ≈200 h. A combination of anion doping and cation doping may provide a highly attractive strategy for the future development of cathode materials.
A novel and facile strategy toward the development of a high‐performance cathode is proposed for the first time to resolve the slow activity of cathode materials by embedding anion ions into the perovskite lattice for intermediate‐temperature solid oxide fuel cells.
Hydrogen production from electrochemical water splitting represents a highly promising technology for sustainable energy storage, but its widespread implementation heavily relies on the development ...of high-performance and cost-effective hydrogen evolution reaction (HER) electrocatalysts. Metal oxides, an important family of functional materials with diverse compositions and structures, were traditionally believed inactive towards HER. Encouragingly, the continuous breakthroughs and significant progress in recent years (mainly from 2015 onwards) make engineered metal oxides emerge as promising candidates for HER electrocatalysis. In this article, we present a comprehensive review of recent advances in metal oxide-based electrocatalysts for HER. We start with a brief description of some key fundamental concepts of HER, such as mechanisms, computational activity descriptors, and experimental parameters used to evaluate catalytic performance. This is followed by a overview of various types of metal oxide-based HER electrocatalysts reported so far, including single transition metal oxides, spinel oxides, perovskite oxides, metal (oxy)hydroxides, specially-structured metal oxides and oxide-containing hybrids, with special emphasis on designed strategies for promoting performance and property-activity correlation. Finally, some concluding remarks and perspectives about future opportunities of this exciting field are provided.
Metal oxide-based materials are emerging as a promising family of hydrogen evolution reaction (HER) electrocatalysts.
Abstract
The state-of-the-art active HER catalysts in acid media (e.g., Pt) generally lose considerable catalytic performance in alkaline media mainly due to the additional water dissociation step. ...To address this issue, synergistic hybrid catalysts are always designed by coupling them with metal (hydro)oxides. However, such hybrid systems usually suffer from long reaction path, high cost and complex preparation methods. Here, we discover a single-phase HER catalyst, SrTi
0.7
Ru
0.3
O
3-δ
(STRO) perovskite oxide highlighted with an unusual super-exchange effect, which exhibits excellent HER performance in alkaline media via atomic-scale synergistic active centers. With insights from first-principles calculations, the intrinsically synergistic interplays between multiple active centers in STRO are uncovered to accurately catalyze different elementary steps of alkaline HER; namely, the Ti sites facilitates nearly-barrierless water dissociation, Ru sites function favorably for OH* desorption, and non-metal oxygen sites (i.e., oxygen vacancies/lattice oxygen) promotes optimal H* adsorption and H
2
desorption.
Layered LiCo0.8Fe0.2O2 demonstrates dramatically enhanced oxygen evolution reaction (OER) activity and durability in an alkaline solution over LiCoO2 and other reported state‐of‐the‐art catalysts, ...including benchmark IrO2. This superior performance is attributed to Fe‐doping‐induced synergistic effects.
The development of highly efficient and low‐cost electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is paramount for water splitting associated with the ...storage of clean and renewable energy. Here, this study reports its findings in the development of a nanostructured perovskite oxide as OER/HER bifunctional electrocatalyst for overall water splitting. Prepared by a facile electrospinning method, SrNb0.1Co0.7Fe0.2O3–δ perovskite nanorods (SNCF‐NRs) display excellent OER and HER activity and stability in an alkaline solution, benefiting from the catalytic nature of perovskites and unique structural features. More importantly, the SNCF‐NR delivers a current density of 10 mA cm−2 at a cell voltage of merely ≈1.68 V while maintaining remarkable durability when used as both anodic and cathodic catalysts in an alkaline water electrolyzer. The performance of this bifunctional perovskite material is among the best ever reported for overall water splitting, offering a cost‐effective alternative to noble metal based electrocatalysts.
A novel SrNb0.1Co0.7Fe0.2O3‐δ perovskite nanorod prepared by a facile electrospinning process exhibits excellent bifunctional electrocatalytic activity for oxygen evolution reaction and hydrogen evolution reaction in alkaline media, delivering an overall water splitting current density of 10 mA cm−2 at a cell voltage of merely ≈1.68 V while maintaining remarkable durability, which is among the best‐performing overall water splitting electrocatalysts reported so far.
Solid oxide fuel cells (SOFCs) have potential to be the cleanest and most efficient electrochemical energy conversion devices with excellent fuel flexibility. To make SOFC systems more durable and ...economically competitive, however, the operation temperature must be significantly reduced, which depends sensitively on the development of highly active electrocatalysts for oxygen reduction reaction (ORR) at low temperatures. Here we report a novel silver nanoparticle-decorated perovskite oxide, prepared via a facile exsolution process from a Sr0.95Ag0.05Nb0.1Co0.9O3‑δ (SANC) perovskite precursor, as a highly active and robust ORR electrocatalyst for low-temperature SOFCs. The exsolved Sr0.95Ag0.05Nb0.1Co0.9O3‑δ (denoted as e-SANC) electrode is very active for ORR, achieving a very low area specific resistance (∼0.214 Ω cm2 at 500 °C). An anode-supported cell with the new heterostructured cathode demonstrates very high peak power density (1116 mW cm–2 at 500 °C) and stable operation for 140 h at a current density of 625 mA cm–2. The superior ORR activity and stability are attributed to the fast oxygen surface exchange kinetics and the firm adhesion of the Ag nanoparticles to the Sr0.95Nb0.1Co0.9O3−δ (SNC0.95) support. Moreover, the e-SANC cathode displays improved tolerance to CO2. These unique features make the new heterostructured material a highly promising cathode for low-temperature SOFCs.
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