Electrochemical water splitting is a critical energy conversion process for producing clean and sustainable hydrogen; this process relies on low‐cost, highly active, and durable oxygen evolution ...reaction/hydrogen evolution reaction electrocatalysts. Metal cations (including transition metal and noble metal cations), particularly high‐valence metal cations that show high catalytic activity and can serve as the main active sites in electrochemical processes, have received special attention for developing advanced electrocatalysts. In this review, heterogenous electrocatalyst design strategies based on high‐valence metal sites are presented, and associated materials designed for water splitting are summarized. In the discussion, emphasis is given to high‐valence metal sites combined with the modulation of the phase/electronic/defect structure and strategies of performance improvement. Specifically, the importance of using advanced in situ and operando techniques to track the real high‐valence metal‐based active sites during the electrochemical process is highlighted. Remaining challenges and future research directions are also proposed. It is expected that this comprehensive discussion of electrocatalysts containing high‐valence metal sites can be instructive to further explore advanced electrocatalysts for water splitting and other energy‐related reactions.
High‐valence metal cations, including transition metal and noble metal cations, exhibit high catalytic activity and serve as the main active sites in electrochemical processes. This review discusses the design strategies, advances, challenges, and future directions of heterogenous electrocatalysts based on high‐valence metal sites for the application of electrochemical water splitting.
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.
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.
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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•Self-supported SnO2 nanoflowers were firstly synthesized on the copper foils.•An amorphous SnO2 layer provides more growth sites and reinforces the adhesion.•The heterostructure ...shows improved performances as a lithium ions battery anode.•The amorphous layer can facilitate the electron transport and buffer the stress.•The self-supported anodes were successfully assembled into flexible cells.
The SnO2 nanoflower arrays were firmly glued on copper collectors by an amorphous SnO2 layer deposited on Cu foils in advance, combining pulsed laser deposition and facile hydrothermal method. As a self-supported anode for Li-ion batteries, the rationally designed heterostructure exhibits excellent electrochemical performance in terms of high specific capacity, good rate capability and improved cycle stability and is successfully assembled into flexible cells made of quasi-solid electrolytes. The improved performance of as-prepared anodes can be attributed to the introducing of the SnO2 buffer layer that provides more growth sites for nanoflowers, assures the solid contact between the active materials and substrate, facilitates electron transport, and furthermore accommodates the internal strain from SnO2 nanoflowers induced by volume change during cycling. The results demonstrate that the electrode shows great promising in high performance Li-ion batteries, especially in the emerging flexible batteries.
•Optimized sham TMS-EEG is introduced and tested.•Sham combined auditory and supramaximal electrical somatosensory stimulation.•Subjects reported equal sensory perception during sham and real ...TMS.•Subtraction revealed evoked EEG potentials and beta-band power specific to real TMS.•The optimized sham procedure is relevant in research and therapeutic settings.
Electroencephalography (EEG) is increasingly used to investigate brain responses to transcranial magnetic stimulation (TMS). A relevant issue is that TMS is associated with considerable auditory and somatosensory stimulation, causing peripherally evoked potentials (PEPs) in the EEG, which contaminate the direct cortical responses to TMS (TEPs). All previous attempts to control for PEPs suffer from significant limitations.
To design an optimized sham procedure to control all sensory input generated by subthreshold real TMS targeting the hand area of the primary motor cortex (M1), enabling reliable separation of TEPs from PEPs.
In 23 healthy (16 female) subjects, we recorded EEG activity evoked by an optimized sham TMS condition which masks and matches auditory and somatosensory co-stimulation during the real TMS condition: auditory control was achieved by noise masking and by using a second TMS coil that was placed on top of the real TMS coil and produced a calibrated sound pressure level. Somatosensory control was obtained by electric stimulation (ES) of the scalp with intensities sufficient to saturate somatosensory input. ES was applied in both the sham and real TMS conditions. Perception of auditory and somatosensory inputs in the sham and real TMS conditions were compared by psychophysical testing. Transcranially evoked EEG signal changes were identified by subtraction of EEG activity in the sham condition from EEG activity in the real TMS condition.
Perception of auditory and somatosensory inputs in the sham vs. real TMS conditions was comparable. Both sham and real TMS evoked a series of similar EEG signal deflections and induced broadband power increase in oscillatory activity. Notably, the present procedure revealed EEG potentials and a transient increase in beta band power at the site of stimulation that were only present in the real TMS condition.
The results validate the effectiveness of our optimized sham approach. Despite the presence of typical responses attributable to sensory input, the procedure provided evidence for direct cortical activation by subthreshold TMS of M1. The findings are relevant for future TMS-EEG experiments that aim at measuring regional brain target engagement controlled by an optimized sham procedure.
Pathological changes and cognitive impairment caused by chronic cerebral hypoperfusion (CCH) have been previously reported. However, how these changes progress remains unclear. Additionally, there ...are few studies regarding the mechanism underlying the involvement of autophagy in these processes. Two-step bilateral common carotid artery occlusion (BCCAO) was performed to replicate CCH in Sprague Dawley rats. The animals were divided into seven groups, including a sham group and 2-, 4-, 8-, 12-, 16-, and 20-week BCCAO groups (
n
= 7 per group). Five additional rats were used to monitor cerebral blood fluid (CBF) changes via laser speckle contrast imaging (LSCI). We tested for cognitive changes and pathological changes, including neuronal injury, white matter lesions, and β-Amyloid (Aβ) deposition, via acknowledged methods. Autophagy was analyzed via western blotting and immunohistochemistry. Cognitive impairment appeared beginning at 8 weeks after BCCAO despite improvement in CBF. Neuronal damage began at 8 weeks in the hippocampal CA1 region and at 4 weeks in the cortex. White matter injury was detected in all BCCAO groups. Intracellular Aβ accumulation occurred earlier than extracellular plaque formation. The levels of autophagy-related proteins (Beclin-1, light chain 3B, and P62) increased beginning at 2 weeks in the cortex and at 4 weeks in the hippocampus and remained elevated throughout the remainder of the study period. Despite recovery of CBF, autophagy dysfunction occurred early after CCH and played an important role in neuronal deterioration, cognitive decline, and intracellular Aβ aggregation.
UAV LiDAR is a powerful tool for rapidly acquiring ground-based 3D spatial information and has been used in various applications. In addition to the ranging mechanism, the scanning method is also an ...important factor, affecting the performance of UAV LiDAR, and the internal angle error of LiDAR will seriously affect its measurement accuracy. Starting from the rotary scanning model of a single-sided mirror, this paper presents a comparative study of the characteristics of 45° single-sided mirror scanning, polygon prism scanning, polygon tower mirror scanning, and wedge mirror scanning. The error sources of the quadrangular tower mirror scanning are analyzed in detail, including the angle deviation between the direction of emitted laser and the rotation axis (typical 0.13 ± 0.18° and 0.85° ± 0.26°), the angle deviation between the mirror’s reflection plane and the rotation axis, and the surface angle deviation between multiple surfaces (typical ± 0.06°). As a result, the measurement deviation caused by the internal angle error can be as high as decimeter to meter, which cannot be fully compensated by simply adjusting the installation angle between the UAV and the LiDAR. After the calibration of the internal angle error, the standard deviation of the elevation difference between the point cloud and the control point is only 0.024 m in the flight experiment at 300 m altitude.
In the context of rapid product iteration, design conflicts arise from discrepancies in designers’ understanding of user needs, influenced by subjective preferences, behavioural stances, and other ...factors. This paper proposes a product conceptual design approach based on the design conflict perspective. First, user comments and design documents are collected. Natural language processing (NLP) methods, including cleaning, filtering, lexical segmentation, feature clustering, and sentiment analysis, are employed to identify design themes. The intuitionistic fuzzy sets (IFSs) and term frequency–inverse document frequency (TF-IDF) algorithms are then utilized to obtain evaluation matrices for the products from both users and designers. Subsequently, design conflicts between users and designers are calculated, and an optimal configuration for product conceptual design is determined through regression analysis and planning methods. Finally, the proposed method is validated using a mobile phone as a product example, and suggestions for product improvement are presented. The results indicate that considering design conflicts as a factor in product design and synthesizing designer and user product concepts enhance the accuracy and reliability of product conceptual design generation. The findings of this study offer new insights into the conceptual design configuration for product iteration.
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