As a highly appealing technology for hydrogen generation, water electrolysis including oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode largely ...depends on the availability of efficient electrocatalysts. Accordingly, over the past years, much effort has been made to develop various electrocatalysts with superior performance and reduced cost. Among them, ruthenium (Ru)-based materials for OER and HER are very promising because of their prominent catalytic activity, pH-universal application, the cheapest price among the precious metal family, and so on. Herein, recent advances in this hot research field are comprehensively reviewed. A general description about water splitting is presented to understand the reaction mechanism and proposed scaling relations toward activities, and key stability issues for Ru-based materials are further given. Subsequently, various Ru-involving electrocatalysts are introduced and classified into different groups for improving or optimizing electrocatalytic properties, with a special focus on several significant bifunctional electrocatalysts along with a simulated water electrolyzer. Finally, a perspective on the existing challenges and future progress of Ru-based catalysts toward OER and HER is provided. The main aim here is to shed some light on the design and construction of emerging catalysts for energy storage and conversion technologies.
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.
To date, it is still a challenge to simultaneously reinforce and well monitor the delamination of carbon fiber reinforced plastics (CFRPs) using nanocarbon-based interleaf due to the high electrical ...conductivity of CFRPs. Herein, this work prepares a novel woven grid composed of carbon nanotubes and graphenes (CG) with various grid densities and suitable resistivity. Results reveal that the CG woven grid-based interleaf could significantly reinforce the interlaminar shear properties of CFRPs, i.e. mode II interlaminar fracture toughness and interlaminar shear strength can be improved by 38–60% and 17–25%, respectively. Meanwhile, the relative resistance change (ΔR/R0%) of CFRPs at the delamination initiation stage can reach ~12% or more, which is greater than that reported by previous literatures. The results suggest that the prepared CG woven grid can not only greatly enhance the delamination resistance, but also can sensitively monitor the delamination of the highly conductive CFRPs.
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•Prepared a novel Carbon nanotube/Graphene woven grid.•Improved mode II interlaminar fracture toughness by 38–60% and interlaminar shear strength by 17–25%.•High resistance variation response to delamination initiation (12% or more).
The single‐phase oxides with elemental complexity and compositional diversity, usually named high entropy oxides, feature homogeneously dispersed multi‐metallic elements in equiatomic concentration. ...The unusual properties of high entropy oxides endow their potential application in clean‐energy‐related electrocatalysis. However, the possible fundamental relationship between configuration entropy and the underlying catalytic mechanism is still not well understood and established. Herein, a high entropy perovskite cobaltate consisting of five equimolar metals in the B‐site (Mg, Mn, Fe, Co, and Ni) is employed as an electrocatalyst for oxygen evolution reaction (OER). The configuration entropy serves as an effective tool to promote the intrinsic activity of the Co reactive site and manipulate the OER mechanism. The high entropy cobaltate demonstrates a lower overpotential of 320 mV at a current density of 10 mA cm−2, outperforming other counterparts. The X‐ray spectroscopies disclose the synergistic charge‐exchange effect among different cations and the formation of a new oxygen hole state. Combinatorially computational and experimental results unveil the enigma that the high configuration entropy leads to the random occupation of cations, facilitates the surface reconstruction, and benefits the formation of stable surface oxygen vacancies. Owing to these merits, the O2 formation is found to be kinetically favorable via the lattice oxygen mechanism.
The configuration entropy is proposed as an effective solution to lower the usage of the expensive element, enhance the intrinsic reactivity, and tune the oxygen evolution reaction mechanism of the perovskite cobaltate electrocatalyst. The entropy effect is closely associated with the inter‐cation charge transfer, creation of oxygen hole states around Ef, and formation of surface oxygen vacancies, granting the material faster reaction kinetics.
Enhancing the level of coupling coordination between the digital economy (DIE) and carbon emission efficiency (CEE) is not only an inevitable choice for achieving the goals of energy conservation and ...emission reduction and promoting green development in China, but also a key path to implementing China's "Double Carbon" strategy. Based on the relevant statistical data of 30 provincial-level regions in China from the period covering 2011 to 2019, this paper empirically analyzed the coupling coordination between the DIE and CEE and its influencing factors. In this study, an improved coupling coordination degree (CCD) model was used to evaluate the degree of the coupling and coordinated development of the DIE and CEE in provincial regions of China. Finally, based on the Technology-Organization-Environment (TOE) framework, a fuzzy-set qualitative comparative analysis (fsQCA) method was employed to identify the realization path of the coupling and coordinated development of the DIE and CEE from the perspective of configuration. The results demonstrated that the coupling coordination between the DIE and CCE in China demonstrated a gradual upward trend, and exhibited regional differences, showing a decreasing trend of east > middle > west. Regarding the influencing factors, no single influencing factor could act as a necessary condition for the high CCD, the coupling and coordinated development of the DIE and CEE is a multifactorial synergy. There were five paths for the high degree of coupling coordination between the DIE and CEE, which were divided into three types: organization-environment-led type, environment-led type, and technology-organization-led type. Furthermore, technological innovation level and industrial structure could substitute for one another in some conditions, and environmental regulation and economic development level were synchronized. These conclusions provide a theoretical basis for countries to formulate policies to promote the coupling and coordinated development of their DIE and CEE.
An ideal solid oxide fuel cell (SOFC) cathode should meet multiple requirements, i.e., high activity for oxygen reduction reaction (ORR), good conductivity, favorable stability, and sound ...thermo‐mechanical/chemical compatibility with electrolyte, while it is very challenging to achieve all these requirements based on a single‐phase material. Herein, a cost‐effective multi‐phase nanocomposite, facilely synthesized through smart self‐assembly at high temperature, is developed as a near‐ideal cathode of intermediate‐temperature SOFCs, showing high ORR activity (an area‐specific resistance of ≈0.028 Ω cm2 and a power output of 1208 mW cm−2 at 650 °C), affordable conductivity (21.5 S cm−1 at 650 °C), favorable stability (560 h operation in single cell), excellent chemical compatibility with Sm0.2Ce0.8O1.9 electrolyte, and reduced thermal expansion coefficient (≈16.8 × 10−6 K−1). Such a nanocomposite (Sr0.9Ce0.1Fe0.8Ni0.2O3–δ) is composed of a single perovskite main phase (77.2 wt%), a Ruddlesden–Popper (RP) second phase (13.3 wt%), and surface‐decorated NiO (5.8 wt%) and CeO2 (3.7 wt%) minor phases. The RP phase promotes the oxygen bulk diffusion while NiO and CeO2 nanoparticles facilitate the oxygen surface process and O2− migration from the surface to the main phase, respectively. The strong interaction between four phases in nanodomain creates a synergistic effect, leading to the superior ORR activity.
A cobalt‐free multi‐phase nanocomposite with a superior electrochemical activity for oxygen reduction is developed as a near‐ideal cathode of intermediate‐temperature solid oxide fuel cells (SOFCs) via a smart self‐assembly strategy. Sr0.9Ce0.1Fe0.8Ni0.2O3–δ is a highly promising cathode material for SOFCs, suitable for the efficient and stable operation at the intermediate‐temperature range.
Here a new strategy is unveiled to develop superior cathodes for protonic ceramic fuel cells (PCFCs) by the formation of Ruddlesden–Popper (RP)‐single perovskite (SP) nanocomposites. Materials with ...the nominal compositions of LaSrxCo1.5Fe1.5O10−δ (LSCFx, x = 2.0, 2.5, 2.6, 2.7, 2.8, and 3.0) are designed specifically. RP‐SP nanocomposites (x = 2.5, 2.6, 2.7, and 2.8), SP oxide (x = 2.0), and RP oxide (x = 3.0) are obtained through a facile one‐pot synthesis. A synergy is created between RP and SP in the nanocomposites, resulting in more favorable oxygen reduction activity compared to pure RP and SP oxides. More importantly, such synergy effectively enhances the proton conductivity of nanocomposites, consequently significantly improving the cathodic performance of PCFCs. Specifically, the area‐specific resistance of LSCF2.7 is only 40% of LSCF2.0 on BaZr0.1Ce0.7Y0.2O3−δ (BZCY172) electrolyte at 600 °C. Additionally, such synergy brings about a reduced thermal expansion coefficient of the nanocomposite, making it better compatible with BZCY172 electrolyte. Therefore, an anode‐supported PCFC with LSCF2.7 cathode and BZCY172 electrolyte brings an attractive peak power output of 391 mW cm−2 and excellent durability at 600 °C.
Ruddlesden–Popper and single perovskite (RP‐SP) nanocomposites are synthesized by a facile one‐pot method. Due to the synergistic effect between the RP and SP phases, the obtained nanocomposite possesses enhanced proton‐conductivity. Therefore, compared with pure RP and SP cathodes, the protonic ceramic fuel cell with this new nanocomposite cathode delivers the best cell performance.
A high‐performance cathode of a protonic ceramic fuel cell (PCFC) should possess excellent oxygen reduction reactivity, high proton/oxygen‐ion/electron conductivity, and sufficient operational ...stability, thus requiring a delicate tuning of both the bulk and surface properties of the electrode material. Although surface modification of perovskites with nanoparticles from reducing‐atmosphere exsolution has been demonstrated effective at improving the electrochemical anodic oxidation, such nanoparticles would easily re‐incorporate into the perovskite lattice causing a big challenge for their application as a cathode. Here, a durable perovskite‐based nanocomposite cathode for PCFCs is reported, which is facilely prepared via the exsolution of nanoparticles in an oxidizing atmosphere. Through composition and cation nonstoichiometry manipulation, a precursor with the nominal composition of Ba0.95(Co0.4Fe0.4Zr0.1Y0.1)0.95Ni0.05O3−δ (BCFZYN‐095) is designed, synthesized, and investigated, which, upon calcination, gives rise to the formation of a perovskite‐based nanocomposite comprising a major perovskite phase and a minor NiO phase enriched on the perovskite surface. The major perovskite phase enabled by the proper cation nonstoichiometry manipulation promotes bulk proton conduction while the NiO nanoparticles facilitate the oxygen surface exchange process, leading to a superior cathodic performance with a maximum peak power density of 1040 mW cm−2 at 650 °C and excellent operational stability of 400 h at 550 °C.
The major perovskite phase, m‐BCFZYN‐095, in BCFZYN‐095 has high proton conductivity, and NiO nanoparticles on the surface effectively improve the oxygen surface exchange rate, thereby simultaneously increasing proton and oxygen ion conductivities of the BCFZYN‐095 composite. Consequently, favorable peak power densities of a protonic ceramic fuel cell with the BCFZYN‐095 composite cathode in H2 are obtained.
Here, we report an oxygen ion-proton-electron-conducting nanocomposite, BaCo0.7(Ce0.8Y0.2)0.3O3-δ (BCCY), derived from a self-assembly process, as a high-performance protonic ceramic fuel cell (PCFC) ...or mixed O2−/H+ dual-ion conducting fuel cell (dual-ion FC) cathode. Self-assembly during high-temperature calcinations results in the formation of a nanocomposite consisting of a mixed H+/e− conducting BaCexYyCozO3-δ (P-BCCY) phase and mixed O2−/e− conducting BaCoxCeyYzO3-δ (M-BCCY) and BaCoO3-δ (BC) phases. The interplay between these phases promotes the oxygen reduction reaction (ORR) kinetics of this composite cathode and improves its thermo-mechanical compatibility by tempering the mismatch in thermal expansion coefficient (TEC). When tested as the cathode in anode-supported dual-ion FCs and PCFCs, peak power densities (PPDs) of 985 and 464 mW cm−2, respectively, are achieved at 650°C while maintaining a robust operational stability of 812 h at 550°C. This material is ideally suited for high-performance cathodes for PCFCs and dual-ion FCs, greatly accelerating the commercialization of this technology.
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•A multi-phase nanocomposite PCFC cathode is derived from the self-assembly process•The nanocomposite shows sufficient oxygen ion, proton, and electron conductivity•Direct experimental measurement method is shown for specific proton conductivity values•The interplay in multi-phase promotes ORR kinetics and reduces thermal expansion
Protonic ceramic fuel cells (PCFCs) have attracted more attention than solid oxide fuel cells based on oxygen-ion-conducting electrolytes that operate at intermediate temperatures due to the lower activation energy for proton conduction than for oxygen ions in oxide electrolytes. However, the practical application of PCFC technology is hindered by the lack of suitable cathode materials. Here, we report our rationally designed triple conducting nanocomposite cathode BaCo0.7(Ce0.8Y0.2)0.3O3-δ with sufficient oxygen ion-proton-electron transfer capability for PCFCs. This work develops the highly active and stable cathode material and simultaneously measures the specific values of oxygen ion, proton, and electron conductivity of the cathode material. This work also highlights the design strategy of perovskite-based electrocatalysts for other energy conversion and storage systems such as water splitting, metal-air batteries, and dye-sensitized solar cells.
A nanocomposite cathode is composed of a mixed H+/e− conducting BaCexYyCozO3-δ (P-BCCY) phase, a mixed O2−/e− conducting BaCoxCeyYzO3-δ (M-BCCY) phase, and a mixed O2−/e− conducting BaCoO3-δ (BC) phase. The P-BCCY phase could promote proton diffusion, the M-BCCY phase could facilitate oxygen ion diffusion, and the BC phase could enhance the electronic conduction of the electrode; the interfaces between the three phases in nano-domain greatly increases the number of active sites for electrochemical reactions.
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