Blocking Ion Migration Stabilizes the High Thermoelectric Performance in Cu2Se Composites

The applications of mixed ionic–electronic conductors are limited due to phase instability under a high direct current and large temperature difference. Here, it is shown that Cu₂Se is stabilized through regulating the behaviors of Cu⁺ ions and electrons in a Schottky heterojunction between the Cu₂Se host matrix and in-situ-formed BiCuSeO nanoparticles. The accumulation of Cu⁺ ions via an ionic capacitive effect at the Schottky junction under the direct current modifies the space-charge distribution in the electric double layer, which blocks the long-range migration of Cu⁺ and produces a drastic reduction of Cu⁺ ion migration by nearly two orders of magnitude. Moreover, this heterojunction impedes electrons transferring from BiCuSeO to Cu₂Se, obstructing the reduction reaction of Cu⁺ into Cu metal at the interface and hence stabilizes the β-Cu₂Se phase. Furthermore, incorporation of BiCuSeO in Cu₂Se optimizes the carrier concentration and intensifies phonon scattering, contributing to the peak figure of merit ZT value of ≈ 2.7 at 973 K and high average ZT value of ≈ 1.5 between 400 and 973 K for the Cu₂Se/BiCuSeO composites. This discovery provides a new avenue for stabilizing mixed ionic–electronic conduction thermoelectrics, and gives fresh insights into controlling ion migration in these ionic-transport-dominated materials.     

A New Class of Proton Conductors with Dramatically Enhanced Stability and High Conductivity for Reversible Solid Oxide Cells

Reversible solid oxide cells based on proton conductors (P-ReSOCs) have potential to be the most efficient and low-cost option for large-scale energy storage and power generation, holding promise as an enabler for the implementation of intermittent renewable energy technologies and the widespread utilization of hydrogen. Here, the rational design of a new class of hexavalent Mo/W-doped proton-conducting electrolytes with excellent durability while maintaining high conductivity is reported. Specifically, BaMo(W)_0.03Ce_0.71Yb_0.26O_3-δ exhibits dramatically enhanced chemical stability against high concentrations of steam and carbon dioxide than the state-of-the-art electrolyte materials while retaining similar ionic conductivity. In addition, P-ReSOCs based on BaW_0.03Ce_0.71Yb_0.26O_3-δ demonstrate high peak power densities of 1.54, 1.03, 0.72, and 0.48 W cm⁻² at 650, 600, 550, and 500 °C, respectively, in the fuel cell mode. During steam electrolysis, a high current density of 2.28 A cm⁻² is achieved at a cell voltage of 1.3 V at 600 °C, and the electrolysis cell can operate stably with no noticeable degradation when exposed to high humidity of 30% H₂O at −0.5 A cm⁻² and 600 °C for over 300 h. Overall, this work demonstrates the promise of donor doping for obtaining proton conductors with both high conductivity and chemical stability for P-ReSOCs.     

High‐Temperature CO2 Electrolysis in Solid Oxide Electrolysis Cells: Developments,Challenges, and Prospects

High‐temperature CO₂ electrolysis in solid‐oxide electrolysis cells (SOECs) could greatly assist in the reduction of CO₂ emissions by electrochemically converting CO₂ to valuable fuels through effective electrothermal activation of the stable C?O bond. If powered by renewable energy resources, it could also provide an advanced energy‐storage method for their intermittent output. Compared to low‐temperature electrochemical CO₂ reduction, CO₂ electrolysis in SOECs at high temperature exhibits higher current density and energy efficiency and has thus attracted much recent attention. The history of its development and its fundamental mechanisms, cathode materials, oxygen‐ion‐conducting electrolyte materials, and anode materials are highlighted. Electrode, electrolyte, and electrode–electrolyte interface degradation issues are comprehensively summarized. Fuel‐assisted SOECs with low‐cost fuels applied to the anode to decrease the overpotential and electricity consumption are introduced. Furthermore, the challenges and prospects for future research into high‐temperature CO₂ electrolysis in SOECs are included.     

A Cobalt-Free Multi-Phase Nanocomposite as Near-Ideal Cathode of Intermediate-Temperature Solid Oxide Fuel Cells Developed by Smart Self-Assembly

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 Sm_0.2Ce_0.8O_1.9 electrolyte, and reduced thermal expansion coefficient (≈16.8 × 10⁻⁶ K⁻¹). Such a nanocomposite (Sr_0.9Ce_0.1Fe_0.8Ni_0.2O_3–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.     

Infiltrated NiCo Alloy Nanoparticle Decorated Perovskite Oxide: A Highly Active,Stable, and Antisintering Anode for Direct‐Ammonia Solid Oxide Fuel Cells

Direct ammonia solid oxide fuel cell (DA‐SOFC) is superior to low‐temperature direct ammonia fuel cell using anion exchange membrane because of much improved anode reaction kinetics at elevated temperature. However, significant performance degradation due to severe sintering of conventional nickel cermet anode under operating conditions is a big challenge for realizing its practical use. Herein, a high‐performance anode based on La_0.55Sr_0.30TiO_3?δ (LST) perovskite substrate with its surface decorated with in situ exsolved and strongly coupled NiCo alloy nanoparticles (NPs) is designed and fabricated for DA‐SOFCs, exhibiting superior catalytic activity for NH₃ decomposition reaction due to balanced NH₃ adsorption and N₂ desorption processes. An electrolyte‐supported single cell with infiltrated NiCo/LST on Sm_0.2Ce_0.8O_1.9 scaffold anode delivers a maximum power density of 361 mW cm^?2 at 800 °C in NH₃ fuel, superior to similar SOFCs with Ni or Co NP‐decorated LST based anodes (161 and 98 mW cm^?2). Furthermore, the SOFC with this newly developed anode displays favorable operational stability without obvious performance degradation at 700 °C for a test period of ≈120 h, attributed to its high antisintering capability. This study provides some strategies to develop highly active, stable, and antisintering perovskite‐based nanocomposite for DA‐SOFCs, facilitating the practical use of this technology.     

Li2O烧结助剂对固体氧化物燃料电池LSGM电解质烧结特性及离子电导率的影响

本工作研究了Li₂O作为烧结助剂对固体氧化物燃料电池La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM)电解质烧结行为的影响规律, 系统表征了烧结助剂含量和烧结温度对LSGM烧结体的致密度、微观组织结构、相组成以及离子电导率的影响。研究结果表明, Li₂O烧结助剂不仅可显著降低LSGM电解质的完全致密化烧结温度, 还可以消除电解质粉体中原有的LaSrGa₃O₇杂相, 并且抑制常规烧结过程中易于产生的MgO杂相, 从而获得较高离子电导率的LSGM块体。当Li元素添加量为摩尔分数1%时, 在1400 ℃烧结4 h 获得的LSGM烧结体, 其体密度达到理论密度的99% 且为单一的钙钛矿结构。烧结体的离子电导率在800 ℃测试温度下达到最大值0.17 S/cm, 相比未添加烧结助剂的试样提升20%以上。上述结果表明, 通过添加适量的Li₂O作为烧结助剂对制备用于中温固体氧化物燃料电池(IT-SOFCs)高离子电导率的电解质具有重要意义。     

Enhancing Electrochemical CO2 Reduction on Perovskite Oxide for Solid Oxide Electrolysis Cells through In Situ A-Site Deficiencies and Surface Carbonate Deposition Induced by Lithium Cation Doping and Exsolution

Solid oxide electrolysis cells (SOECs) hold enormous potential for efficient conversion of CO₂ to CO at low cost and high reaction kinetics. The identification of active cathodes is highly desirable to promote the SOEC's performance. This study explores a lithium-doped perovskite La_0.6-xLi_xSr_0.4Co_0.7Mn_0.3O_3-δ (x = 0, 0.025 0.05, and 0.10) material with in situ generated A-site deficiency and surface carbonate as SOEC cathodes  for CO₂ reduction. The experimental results indicate that the SOEC with the La_0.55Li_0.05Sr_0.4Co_0.7Mn_0.3O_3-δ cathode exhibits a current density of 0.991 A cm⁻² at 1.5 V/800 °C, which is an improvement of ≈30% over the pristine sample. Furthermore, SOECs based on the proposed cathode demonstrate excellent stability over 300 h for pure CO₂ electrolysis. The addition of lithium with high basicity, low valance, and small radius, coupled with A-site deficiency, promotes the formation of oxygen vacancy and modifies the electronic structure of active sites, thus enhancing CO₂ adsorption, dissociation process, and CO desorption steps as corroborated by the experimental analysis and the density functional theory calculation. It is further confirmed that Li-ion migration to the cathode surface forms carbonate and consequently provides the perovskite cathode with an impressive anti-carbon deposition capability, as well as electrolysis activity.     

Graphene‐Based Nafion Nanocomposite Membranes: Enhanced Proton Transport and Water Retention by Novel Organo‐functionalized Graphene Oxide Nanosheets

Novel nanostructured organo‐modified layered materials based on graphene oxide carrying various hydrophilic functional groups (‐NH₂, ‐OH, ‐SO₃H) are prepared and tested as nanofillers for the creation of innovative graphene‐based Nafion nanocomposites. The hybrid membranes are characterized by a combination of analytical techniques, which show that highly homogeneous exfoliated nanocomposites are created. The pulsed field gradient NMR technique is used to measure the water self‐diffusion coefficients. Remarkable behavior at temperatures up to 140 °C is observed for some composite membranes, thereby verifying the exceptional water retention property of these materials. Dynamic mechanical analysis shows that hybrid membranes are much stiffer and can withstand higher temperatures than pure Nafion.     

Tailoring the Cathode–Electrolyte Interface with Nanoparticles for Boosting the Solid Oxide Fuel Cell Performance of Chemically Stable Proton‐Conducting Electrolytes

Solid oxide fuel cells (SOFCs) represent the most efficient devices for producing electrical power from fuels. The limit in their application is due to the high operation temperature of conventional SOFC materials. Progress is made toward lower operating temperatures using alternative oxygen‐ion conducting electrolytes, but problems of stability and electronic conductivity still remain. A promising alternative is the use of chemically stable proton‐conducting Y‐doped BaZrO₃ (BZY) electrolytes, but their practical applications are limited by the BZY's relatively low performance. Herein, it is reported that deposition by impregnation of cathode nanoparticles on BZY backbones provides a powerful strategy to improve the BZY‐based SOFC performance below 600 °C, allowing an outstanding power output for this chemically stable electrolyte. Moreover, it is demonstrated that keeping the nanostructure is more important than keeping the desired chemical composition. The proposed scalable processing method can make BZY a competitive electrolyte for SOFC applications.     

固体氧化物燃料电池Sr系钙钛矿电极B位元素成分优化规律

采用第一性原理, 对元素周期表中3~6周期52种元素作为固体氧化物燃料电池(SOFC) Sr为A位系列钙钛矿结构电极材料B位替换元素的相关结构相的结合能进行了系统计算, 据此分析了各元素对生成立方相和六方相结构稳定性影响的趋势。通过对相关体系的成分比例进行推算, 讨论了这些实验体系在稳定性趋势图中的分布规律, 进一步对上述体系的实验数据进行分析, 得到了以Mo-Fe-Co连线为中心的成分优化区域。根据相关氧离子扩散模型的计算, 结果显示该区域形成的原因与氧空位形成能、迁移能以及禁带宽度均较为适中有关。以上理论结合实验的研究为电极材料的成分优化提供了理论指导。     

Li2O助烧的Gd0.1Ce0.9O1.95烧结过程及其电导性能研究

氧化铈基电解质是中低温固体氧化物燃料电池最常用的材料之一。本研究利用密度泛函理论计算方法阐述了Li₂O和CeO₂分子之间的相互作用, 计算结果表明Li₂O对CeO₂具有助烧作用。在此基础上, 在氧化铈基电解质Gd_0.1Ce_0.9O_1.95(GDC)中掺入不同比例(0~5mol%)Li₂O, 通过烧结曲线测试及扫描电镜分析了其实际烧结过程, 并对其电化学性能进行了研究。实验结果表明, 添加Li₂O后, GDC的烧结开始收缩温度明显向低温偏移, 随掺杂量的增加, 最大收缩速率的温度也逐渐降低, 其中掺入2.5mol%Li₂O-GDC在650 ℃就开始迅速收缩, 900 ℃时相对致密度在99%以上; 添加Li₂O后, GDC总电导率提高, 同时电池开路电压没有降低。因此, Li₂O是一种很好的燃料电池氧化铈基电解质的助烧剂, 具有很好的应用前景。     

Li‐Ion Cooperative Migration and Oxy‐Sulfide Synergistic Effect in Li14P2Ge2S16−6xOx Solid‐State‐Electrolyte Enables Extraordinary Conductivity and High Stability

Critical to the development of all‐solid‐state lithium‐ion batteries technology are novel solid‐state electrolytes with high ionic conductivity and robust stability under inorganic solid‐electrolyte operating conditions. Herein, by using density functional theory and molecular dynamics, a mixed oxygen‐sulfur‐based Li‐superionic conductor is screened out from the local chemical structure of β‐Li₃PS₄ to discover novel Li₁₄P₂Ge₂S₈O₈ (LPGSO) with high ionic conductivity and high stability under thermal, moist, and electrochemical conditions, which causes oxygenation at specific sites to improve the stability and selective sulfuration to provide an O‐S mixed path by Li‐S/O structure units with coordination number between 3 and 4 for fast Li‐cooperative conduction. Furthermore, LPGSO exhibits a quasi‐isotropic 3D Li‐ion cooperative diffusion with a lesser migration barrier (≈0.19 eV) compared to its sulfide‐analog Li₁₄P₂Ge₂S₁₆. The theoretical ionic conductivity of this conductor at room temperature is as high as ≈30.0 mS cm^?1, which is among the best in current solid‐state electrolytes. Such an oxy‐sulfide synergistic effect and Li‐ion cooperative migration mechanism would enable the engineering of next‐generation electrolyte materials with desirable safety and high ionic conductivity, for possible application in the near future.     

2D Materials Decorated with Ultrathin and Porous Graphene Oxide for High Stability and Selective Surface Activity

2D black phosphorus (BP) and MXenes have triggered enormous research interest in catalysis, energy storage, and chemical sensing. Unfortunately, the low stability of these materials under practical operating conditions remains a critical bottleneck, particularly as they are prone to oxidization under moisture. In this work, the design and application of stable 2D heterostructures obtained from decorating BP and MXene (Ti₃C₂T_x) with few-layer holey graphene oxide (FHGO) membranes are presented. In the resulting heterostructured systems, FHGO serves as a multifunctional passivation layer that shields BP or MXene from oxidative degradation, while allowing the selective diffusion of target gas molecules through its micropores and toward the underlying 2D material. Through a case study of dilute NO₂ sensing, it is demonstrated that these heterostructures show a greatly enhanced sensing performance under humid conditions, where fast sensing speed and response are consistently observed, and high stability is impressively retained upon repetitive sensing cycles for 1000 min. These results corroborate the efficacy of material decoration with porous FHGO membranes and suggest that this is a generalizable strategy for reliable high-performance applications of 2D materials.     

低温固体氧化物燃料电池新型CeO2基复合电解质研究

采用一种钐掺杂的氧化铈(SDC)-碳酸盐复合物作为低温固体氧化物燃料电池(LTSOFC)的电解质.利用交流阻抗测试400～700℃不同气氛下的导电性能t电解质的电导率在大约500℃发生突变,表明传导机理发生改变;500℃以上电导率随碳酸盐组分增加而增大;还原性气氛下的电导率高于氧化性气氛下的电导率.以不同碳酸盐含量的电解质材料制备阳极支撑型单电池,运行中发现,在阴极和阳极侧均有水产生,说明同时存在氧离子和质子传导.电流-电压特性和功率特性显示,所有复合物电解质均有优于纯SDC电解质的电池性能,其中碳酸盐含量为20wt%时性能最好, 500℃开路电压为1.00V,最大功率密度达415mW·cm-2>.     

Highly Efficient and Stable GABr-Modified Ideal-Bandgap (1.35 eV) Sn/Pb Perovskite Solar Cells Achieve 20.63% Efficiency with a Record Small Voc Deficit of 0.33 V

1.5–1.6 eV bandgap Pb-based perovskite solar cells (PSCs) with 30–31% theoretical efficiency limit by the Shockley–Queisser model achieve 21–24% power conversion efficiencies (PCEs). However, the best PCEs of reported ideal-bandgap (1.3–1.4 eV) Sn–Pb PSCs with a higher 33% theoretical efficiency limit are <18%, mainly because of their large open-circuit voltage (V_oc) deficits (>0.4 V). Herein, it is found that the addition of guanidinium bromide (GABr) can significantly improve the structural and photoelectric characteristics of ideal-bandgap (≈1.34 eV) Sn–Pb perovskite films. GABr introduced in the perovskite films can efficiently reduce the high defect density caused by Sn²⁺ oxidation in the perovskite, which is favorable for facilitating hole transport, decreasing charge-carrier recombination, and reducing the V_oc deficit. Therefore, the best PCE of 20.63% with a certificated efficiency of 19.8% is achieved in 1.35 eV PSCs, along with a record small V_oc deficit of 0.33 V, which is the highest PCE among all values reported to date for ideal-bandgap Sn–Pb PSCs. Moreover, the GABr-modified PSCs exhibit significantly improved environmental and thermal stability. This work represents a noteworthy step toward the fabrication of efficient and stable ideal-bandgap PSCs.