A Universal Self-Propagating Synthesis of Aluminum-Based Oxyhalide Solid-State Electrolytes.

Inorganic solid-state electrolytes (SSEs) play a vital role in high-energy all-solid-state batteries (ASSBs). However, the current method of SSE preparation usually involves high-energy mechanical ball milling and/or a high-temperature annealing process, which is not suitable for practical application. Here, a facile strategy is developed to realize the scalable synthesis of cost-effective aluminum-based oxyhalide SSEs, which involves a self-propagating method by the exothermic reaction of the raw materials. This strategy enables the synthesis of various aluminum-based oxyhalide SSEs with tunable components and high ionic conductivities (over 10-3 S cm-1 at 25 °C) for different cations (Li+, Na+, Ag+). It is elucidated that the amorphous matrix, which mainly consists of various oxidized chloroaluminate species that provide numerous sites for smooth ion migration, is actually the key factor for the achieved high conductivities. The application of these aluminum-based oxyhalide SSEs synthesized by our approach further pushes forward their practical application considering their easy synthesis, low cost, and low weight that ensures high-energy-density ASSBs.

Interface synergism and engineering of Pd/Co@N-C for direct ethanol fuel cells.

Direct ethanol fuel cells have been widely investigated as nontoxic and low-corrosive energy conversion devices with high energy and power densities. It is still challenging to develop high-activity and durable catalysts for a complete ethanol oxidation reaction on the anode and accelerated oxygen reduction reaction on the cathode. The materials' physics and chemistry at the catalytic interface play a vital role in determining the overall performance of the catalysts. Herein, we propose a Pd/Co@N-C catalyst that can be used as a model system to study the synergism and engineering at the solid-solid interface. Particularly, the transformation of amorphous carbon to highly graphitic carbon promoted by cobalt nanoparticles helps achieve the spatial confinement effect, which prevents structural degradation of the catalysts. The strong catalyst-support and electronic effects at the interface between palladium and Co@N-C endow the electron-deficient state of palladium, which enhances the electron transfer and improved activity/durability. The Pd/Co@N-C delivers a maximum power density of 438 mW cm-2 in direct ethanol fuel cells and can be operated stably for more than 1000 hours. This work presents a strategy for the ingenious catalyst structural design that will promote the development of fuel cells and other sustainable energy-related technologies.

Evaluation of the impacts of human activities on propagation from meteorological drought to hydrological drought in the Weihe River Basin, China.

Understanding the relationship among different types of drought is crucial for drought mitigation and early warnings. Much attention has been recently focused on the propagation from meteorological drought (MD) to hydrological drought (HD); however, the influences of human activities on drought propagation have rarely been explored. The novelty of the study was to propose an effective framework to quantify the impacts of human activities on MD-HD propagation. We adopted the framework to comprehensively evaluate the anthropic impacts on hydrological drought variations and time, thresholds, and probabilities of MD-HD propagation in the Weihe River Basin (WRB) during different periods. The results showed that human activities did significantly disturb HD variations and MD-HD propagation characteristics. Specifically, human activities increased the frequency and extremes of HD and weakened its correlation with MD. The MD-HD propagation characteristics showed spatiotemporal differences across three subbasins because of the different levels of human activities. The thresholds of MD triggering different levels of HD generally became larger with change rates from 1% to 143% and 3% to more than 189% during two periods, respectively. Meanwhile, we also found that the thresholds became distinctly smaller, which could only be observed in spring and winter. Moreover, the relationship between natural and human-induced probabilities of HD occurrence showed three patterns with the increase of MD severity. The quantitative results of this study can provide guide information on adaptation strategies to promote drought preparedness in the WRB. The proposed framework can be also applied in other regions to improve the understanding of hydrological drought mechanisms.

CO2 Bubble-Assisted Pt Exposure in PtFeNi Porous Film for High-Performance Zinc-Air Battery.

Fine-tuning the exposed active sites of platinum group metal (PGM)-based materials is an efficient way to improve their electrocatalytic performance toward large-scale applications in renewable energy devices such as Zn-air batteries (ZABs). However, traditional synthetic methods trade off durability for the high activity of PGM-based catalysts. Herein, a novel dynamic CO2-bubble template (DCBT) approach was established to electrochemically fine-tuning the exposed Pt active sites in PtFeNi (PFN) porous films (PFs). Particularly, CO2 bubbles were intentionally generated as gas-phase templates by methanol electrooxidation. The generation, adsorption, residing, and desorption of CO2 bubbles on the surface of PFN alloys were explored and controlled by adjusting the frequency of applied triangular-wave voltage. Thereby, the surface morphology and Pt exposure of PFN PFs were controllably regulated by tuning the surface coverage of CO2 bubbles. Consequently, the Pt1.1%Fe8.8%Ni PF with homogeneous nanoporous structure and sufficiently exposed Pt active sites was obtained, showing preeminent activities with a half-wave potential (E1/2) of 0.87 V and onset overpotential (ηonset) of 288 mV at 10 mA cm-2 for oxygen reduction and evolution reactions (ORR and OER), respectively, at an ultralow Pt loading of 0.01 mg cm-2. When tested in ZABs, a high power density of 175.0 mW cm-2 and a narrow voltage gap of 0.64 V were achieved for the long cycling tests over 500 h (750 cycles), indicating that the proposed approach can efficiently improve the activity of PGM catalysts by fine-tuning the microstructure without compromising the durability.

Dual-Doping and Synergism toward High-Performance Seawater Electrolysis.

Hydrogen (H2 ) production from direct seawater electrolysis is an economically appealing yet fundamentally and technically challenging approach to harvest clean energy. The current seawater electrolysis technology is significantly hindered by the poor stability and low selectivity of the oxygen evolution reaction (OER) due to the competition with chlorine evolution reaction in practical application. Herein, iron and phosphor dual-doped nickel selenide nanoporous films (Fe,P-NiSe2 NFs) are rationally designed as bifunctional catalysts for high-efficiency direct seawater electrolysis. The doping of Fe cation increases the selectivity and Faraday efficiency (FE) of the OER. While the doping of P anions improves the electronic conductivity and prevents the dissolution of selenide by forming a passivation layer containing P-O species. The Fe-dopant is identified as the primary active site for the hydrogen evolution reaction, and meanwhile, stimulates the adjacent Ni atoms as active centers for the OER. The experimental analyses and theoretical calculations provide an insightful understanding of the roles of dual-dopants in boosting seawater electrolysis. As a result, a current density of 0.8 A cm-2 is archived at 1.8 V with high OER selectivity and long-term stability for over 200 h, which surpasses the benchmarking platinum-group-metals-free electrolyzers.

Surface self-reconstructed amorphous/crystalline hybrid iron disulfide for high-efficiency water oxidation electrocatalysis.

Hybrid electrocatalysts derived from surface self-reconstruction during reaction processes can facilitate charge transfer between different phases and nanostructures by their unique interfaces. Herein, amorphous/crystalline hybrid iron disulfide obtained by self-reconstruction is developed for the first time for the oxygen evolution reaction (OER). The amorphous/crystalline hybrid FeS2 catalyst exhibited a high OER activity with an overpotential of only 189.5 mV (IR-corrected) to deliver 10 mA cm-2 in 1.0 M KOH, which was superior to that of the commercial RuO2. Notably, in the two-electrode system with the amorphous/crystalline hybrid FeS2 as the anode electrocatalyst and Pt/C as the cathode, the catalytic activity towards the overall water splitting was enhanced with a voltage of only 1.43 V at 10 mA cm-2. The phase, composition and surface structure were changed greatly before and after the reaction. All these surface reconstructions after the OER reaction may play significant roles in the high electronic catalytic efficiency. Therefore, the study of the surface reconstruction of catalysts during the reaction process is very important for the structure-performance relationship and the design of efficient hybrid electrocatalysts.

Stabilization of Sn Anode through Structural Reconstruction of a Cu-Sn Intermetallic Coating Layer.

The metallic tin (Sn) anode is a promising candidate for next-generation lithium-ion batteries (LIBs) due to its high theoretical capacity and electrical conductivity. However, Sn suffers from severe mechanical degradation caused by large volume changes during lithiation/delithiation, which leads to a rapid capacity decay for LIBs application. Herein, a Cu-Sn (e.g., Cu3 Sn) intermetallic coating layer (ICL) is rationally designed to stabilize Sn through a structural reconstruction mechanism. The low activity of the Cu-Sn ICL against lithiation/delithiation enables the gradual separation of the metallic Cu phase from the Cu-Sn ICL, which provides a regulatable and appropriate distribution of Cu to buffer volume change of Sn anode. Concurrently, the homogeneous distribution of the separated Sn together with Cu promotes uniform lithiation/delithiation, mitigating the internal stress. In addition, the residual rigid Cu-Sn intermetallic shows terrific mechanical integrity that resists the plastic deformation during the lithiation/delithiation. As a result, the Sn anode enhanced by the Cu-Sn ICL shows a significant improvement in cycling stability with a dramatically reduced capacity decay rate of 0.03% per cycle for 1000 cycles. The structural reconstruction mechanism in this work shines a light on new materials and structural design that can stabilize high-performance and high-volume-change electrodes for rechargeable batteries and beyond.

Programmable Exposure of Pt Active Facets for Efficient Oxygen Reduction.

To produce efficient ORR catalysts with low Pt content, PtNi porous films (PFs) with sufficiently exposed Pt active sites were designed by an approach combining electrochemical bottom-up (electrodeposition) and top-down (anodization) processes. The dynamic oxygen-bubble template (DOBT) programmably controlled by a square-wave potential was used to tune the catalyst morphology and expose Pt active facets in PtNi PFs. Surface-bounded species, such as hydroxyl (OH* , *=surface site) on the exposed PtNi PFs surfaces were adjusted by the applied anodic voltage, further affecting the dynamic oxygen (O2 ) bubbles adsorption on Pt. As a result, PtNi PF with enriched Pt(111) facets (denoted as Pt3.5 % Ni PF) was obtained, showing prominent ORR activity with an onset potential of 0.92 V (vs. RHE) at an ultra-low Pt loading (0.015 mg cm-2 ).

Integration of Au nanoparticles with a g-C3N4 based heterostructure: switching charge transfer from type-II to Z-scheme for enhanced visible light photocatalysis.

Here, we demonstrate that a type-II g-C3N4 nanosheet (CNNS)/W18O49 heterostructure composite can be switched to Z-scheme through the deposition of Au nanoparticles (NPs) on the surface of CNNS. As a direct result, the designed Au/CNNS/W18O49 heterostructure shows enhanced photocatalytic performance for Cr(vi) reduction than the CNNS/W18O49 heterostructure and single components (CNNS and W18O49) under visible light irradiation.

A bismuth based layer structured organic-inorganic hybrid material with enhanced photocatalytic activity.

A bismuth-based organic-inorganic hybrid material with layered structure (BiO-BTCIE) was synthesized by taking advantage of an ion exchange reaction. The structure of BiO-BTCIE was examined by XRD, EXAFS, FT-IR, TG/DTA, etc. By replacing the HCOO(-) with BTC anions in the Bi2O2(2+) interlayer, the Bi2O2(2+) layer is distorted as revealed by the EXAFS, which lead to a longer life time of the photogenerated charge carriers and a higher photocatalytic activity of BiO-BTCIE (more than 10 times).

A novel metal-organic framework based on bismuth and trimesic acid: synthesis, structure and properties.

A bismuth based metal-organic framework ([Bi(BTC)(DMF)]·DMF (CH3OH)2, Bi-BTC) with a novel topology structure is synthesized by a solvothermal method. Bi-BTC crystalizes in the P21/n space group, exhibits a novel 3D framework consisting of trimesic acid (H3BTC) linked with {Bi2O14} units and contains two helix chains which assemble regularly. In addition, we investigated the photophysical properties of Bi-BTC which shows high activity of O2 production in photocatalysis.

A bismuth-based metal-organic framework as an efficient visible-light-driven photocatalyst.

A visible-light-responsive bismuth-based metal-organic framework (Bi-mna) is demonstrated to show good photoelectric and photocatalytic properties. Combining experimental and theoretical results, a ligand-to-ligand charge transfer (LLCT) process is found to be responsible for the high performance, which gives rise to a longer lifetime of photogenerated charge carriers. Our results suggest that bismuth-based MOFs could be promising candidates for the development of efficient visible-light photocatalysts.