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To maximize fuel cell performance, transport pathways for electrons, ions, and reactants should be connected well. This demands a well-constructed microstructure in the catalyst layer (CL). Herein we design and optimize a cathode CL for a direct ammonia fuel cell (DAFC) using a perovskite oxide as the catalyst to reduce reliance on platinum group metals (PGMs). The effects of tailoring carbon, ionomer, and polytetrafluoroethylene (PTFE) content in cathode CLs (CCLs) were explored, and several DAFCs were tested. Using the same catalyst and operating conditions, the lowest maximum current density and peak power density obtained were 85.3 mA cm

Li–S batteries hold great promise for electric vehicles but complex reaction mechanisms during operation have, to date, prevented commercialization.In situtechniques provide insights that may overcome these limitations.

An aqueous Zn-MnO2 battery with high energy density and good cyclability has been successfully developed with use of an ‘oversaturated gel electrolyte’ (OSGE) prepared by cost-effective acetates and poly(acrylic acid) at 75°C. The electrochemical stability window of the OSGE was extended to 3.45 V at room temperature and was able to maintain this window in temperatures up to 80°C. The ionic conductivity of the OSGE was 3.74 × 10−3 S•cm−1 at room temperature. Molecular dynamics simulation was employed to investigate the contacted cation solvation sheath and could be used to account for the excellent stability of the acetate OSGE. On utilisation of the electrolyte, a high reversibility was demonstrated at room temperature, with 600-hour stripping/plating on Zn metal electrodes and no formation of dendrites. The Zn-MnO2 battery successfully operated for 2000 cycles under an over-charge working voltage (2.0 V). This study not only overcomes the limitation associated with the solubility of salts, but also provides a feasible route for developing a highly stable aqueous Zn-MnO2 battery.

As a consequence of the depletion of fossil fuels and an increasing population, the global energy crisis has driven researchers to explore innovative energy storage and conversion (ESC) devices, such as fuel cells, electrolyzers and chemical looping systems. In order to enhance the energy conversion efficiency of these electrochemical devices, high performance and stable electrocatalysts are essential to accelerate the sluggish electrochemical kinetics, e.g. oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and redox reaction. In recent years, as cost-effective and high-efficient catalysts, perovskite oxides have attracted much attention. In addition, the potential of perovskite electrocatalysts may be further boosted due to their flexible composition and tunable electronic structures. This review provides the readers with a comprehensive understanding and updated information of improvements towards the electrocatalytic performances of perovskite oxides. It will focus on research papers regarding low to intermediate temperature electrochemical devices, e.g., water splitting, fuel cells, chemical looping technology and three-way catalysis (TWC) published over the last five years. Various design strategies for optimizing the conductivity and catalytic activity of perovskite are discussed in detail. In the end, this review discusses challenges for the future researches in regard to perovskite based electrocatalysts.

OH- and H+ ionic conductors are important electrolyte materials for electrochemical devices such as fuel cells. The high cost of the best low temperature H+ ionic conductor, Nafion membrane, and the poor chemical compatibility with CO2 in air of alkaline membrane based on quaternary ammonium groups have seriously affected the large-scale application of low temperature fuel cells. Here we show the discovery of a fast ceramic mixed OH-/H+ conductor, perovskite oxide SrZr0.8Y0.2O3-δ, which exhibits a high ionic conductivity of approximately 0.01 S cm-1 at 90°C when measured in water and wet air, sufficient to be used as electrolyte for low temperature fuel cells. The ionic conductivity is stable in wet air during the measured 130 hours. The ionic conduction was also demonstrated by near ambient temperature solid oxide fuel cells (NAT-SOFCs). This opens a window on discovering new ionic conducting materials for low temperature fuel cells.

N,N-Dimethylacetamide (DMA) cooperated with LiNO3 salt has previously shown to be a promising electrolyte for a Li//O2 battery, showing good stability against both the O2 electrode reaction and Li stripping/plating. In this work, DMA is hybridized with a concentrated nitrate electrolyte [2.5 m Zn(NO3)2 + 13 m LiNO3 aqueous solution] for better electrochemical stability while using less dissolved salts. The widest electrochemical stability window for this DMA-diluted electrolyte is determined as 3.1 V, the negative critical stability potential of which is -1.6 V versus Ag/AgCl, indicating desirable stability against hydrogen evolution and Zn deposition. The findings can be attributed to the weakened Li+/Zn2+ solvation sheath caused by low permittivity of DMA, as revealed through Raman spectra characterization and molecular dynamics simulation. A Zn//Zn symmetrical cell and Zn//LiMn2O4 hybrid ion batteries are assembled in air directly, attributed to the stability of DMA toward O2. Zn stripping/plating with a dendrite-free morphology is delivered for 110 h and 200 charge/discharge cycles under 1 C rate, achieving 99.0% Coulombic efficiency. The maximum capacity of the battery is 121.0 mA h·g-1 under 0.2 C rate (based on the mass of LiMn2O4), delivering an energy density of 165.8 W h·kg-1 together with 2.0 V working voltage. This work demonstrates the feasibility and validity of utilizing a relatively dilute electrolyte dissolved in oxygen for a highly stable aqueous rechargeable battery.

Wastewater can contain high amounts of ammonia which can pose as a great safety threat if released into natural waters. The electrochemical oxidation of ammonia offers a viable strategy to remove high concentrations and provides an attractive method for wastewater treatment. However, finding a highly efficient and low-cost catalyst is imperative for overcoming the sluggish nature of ammonia oxidation reaction. Herein, a modified A- and B-site perovskite is proposed as a catalyst for the oxidation of ammonia, making it suitable as an anode in an ammonia electrolyser. A series of La1-yNi0.6Cu0.4-xFexO3-δ (x = 0, 0.05 and 0.10; y = 0, 0.05 and 0.10) perovskite materials were synthesised by a conventional sol–gel method. Amongst those tested oxides, La0.9Ni0.6Cu0.35Fe0.05O3-δ was found to have superior activity towards the electrooxidation of ammonia due to an optimised amount of Fe doping and the presence of oxygen vacancies introduced by an A-site deficiency. Subsequently, La0.9Ni0.6Cu0.35Fe0.05O3-δ was employed as an anode in an ammonia electrolyser where the ammonia removal efficiency reached 95.4 % in simulated wastewater after 80 hr and a substantial reduction in real wastewater was also observed. These results demonstrate that the A-site deficient perovskite materials are a viable electrode for the removal of ammonia in a practical energy setting and paves way for future applications.

The energy density of an aqueous rechargeable battery is closely related to the working voltage which is limited by electrochemcial stability windows of aquoese electrolytes. In this study, an ‘oversaturated gel electrolyte’ (OSGE) is simply prepared with poly(vinyl alcohol) and cost-effective lithium nitrate saturated at 95 oC. The excess salt is then crystallized at room temperature, which is dispersed equally by the continuous room-temperature saturated gel, forming the heterogeneous morphology. The electrochemical stability window is further extended through the transition of interaction between lithium ion and water molecular, solidifying the whole electrolyte, while the high ionic conductivity is basically retained. The electrochemical stability window is 3.2 V (-1.25 to 1.95 V vs. Ag/AgCl) for LiNO3 OSGE with an ionic conductivity of 2.51×10−2 S•cm−1. To explain the wider electrochemical stability window of OSGE, Li ion solvation sheath is built through molecular dynamics (MD) simulation, of which OSGE owns less coordination number between Li ion and water molecular with a shortened distance between Li ion and NO3−, which is consistent with experimental results. A coin cell with working voltage of 2.5 V has been assembled with VO2 nanobelt anode, and LiNi0.5Mn1.5O4 hollow sphere cathode. The LiNi0.5Mn1.5O4 cathode was stabilized by LiNO3 OSGE for 700 cycles with almost 99% coulombic efficiency and the highest energy density of 175.9 Wh•kg−1 (based on the active matter of both anode and cathode). Moreover, the stability window of OSGE is still wide enough at elevated temperatures even at 80 oC, ensuring the desired stability of the VO2/LiMn2O4 battery with 2.0 V working voltage cycling at higher temperatures. Meanwhile, the universality and practicability are demonstrated by employing layered cathodes and thick electrodes in the OSGE-based system. This work provides a new route for utilizing the inexpensive inorganic salts with relatively low solubility in water into super-concentrated electrolyte systems via developing nitrated-based OSGEs for aqueous batteries with high voltage, high energy density and good stability.

Conventional technologies are largely powered by fossil fuel exploitation and have ultimately led to extensive environmental concerns. Hydrogen is an excellent carbon-free energy carrier, but its storage and long-distance transportation remain big challenges. Ammonia, however, is a promising indirect hydrogen storage medium that has well-established storage and transportation links to make it an accessible fuel source. Moreover, the notion of ‘green ammonia’ synthesised from renewable energy sources is an emerging topic that may open significant markets and provide a pathway to decarbonise a variety of applications reliant on fossil fuels. Herein, a comparative study based on the chosen design, working principles, advantages and disadvantages of direct ammonia fuel cells is summarised. This work aims to review the most recent advances in ammonia fuel cells and demonstrates how close this technology type is to integration with future applications. At present, several challenges such as material selection, NOx formation, CO2 tolerance, limited power densities and long term stability must still be overcome and are also addressed within the contents of this review.

In battery systems, aqueous electrolytes are superior in ionic conductivity, interfacial wettability, safety and environmentally benign compared to organic liquids, polymers, inorganic solid-state and ionic liquid electrolytes.

Ammonia contaminated wastewater poses a great hazard to the safety and quality of water resources. Use of ammonia fuel cells to remove ammonia from wastewater is a promising strategy, which not onl...

Developing cost-effective and high-performance electrocatalysts for hydrogen evolution reaction (HER) in all pH conditions is of great significance for scalable and sustainable hydrogen production through electrochemical water splitting. Herein, a novel hybrid composed of RuCo alloy bimodal nanoparticles embedded in N-doped carbon was prepared from pillar-layered chiral metal–organic frameworks via one facile encapsulation-pyrolysis strategy. Due to the unique hybrid structure and composition, the optimized RuCo@NC-600 (prepared at a pyrolysis temperature of 600 °C) catalyst exhibits outstanding HER catalytic activities in alkaline, acidic, and neutral media. Remarkably, the RuCo@NC-600 achieves a current density of 10 mA cm−2 at extremely low overpotentials of 34, 6 and 60 mV in 1.0 M KOH, 0.5 M H2SO4 and 1.0 M PBS solutions, respectively, superior to the benchmark Pt/C catalyst. In addition, a symmetric two-electrode alkaline electrolyzer device pairing RuCo@NC-600 as both cathode and anode displays excellent performance, along with an impressive stability without noticeable attenuation up to 120 h. This work paves the way to the rational development of efficient pH-universal HER electrocatalysts.

In this article, hematite α-Fe2O3 was used as the precursor for the iron-based ammonia synthesis catalyst. Ce0.8Sm0.2O2−δ (SDC), with extrinsic oxygen vacancies was used as a promoter for forming an Fe–SDC composite catalyst. The new Fe–SDC catalyst achieves both high catalytic activity and excellent oxygenate tolerance, working with excellent stability at a feed-gas purity of 99.996%. At 500 °C, 10 MPa for the 80% Fe–20% SDC catalyst, and 15 MPa for the industrial Fe catalysts, and at an impurity level of 150 ppm, with known injected 107.5 ppm O2, the activity of Fe–SDC retains 47.3% of that measured in purified gases while it is only 26.4% and 7.6% for the wustite and magnetite – based industrial Fe catalysts respectively. It is believed that the introduction of extra extrinsic oxygen vacancies strengthen the strong metal-support interaction (SMSI), preventing the growth of formed Fe particles, leading to excellent stability and high tolerance to oxygenates. The SMSI between Fe and oxygen vacancies in SDC may also help to weaken and break the strong NN bonds in N2, increasing the catalytic activity. The use of promoters with extrinsic oxygen and potentially other anion vacancies provides a new strategy to develop oxygenate tolerant catalysts for efficient synthesis of ammonia from less pure feed gases at reduced pressures.

Ammonia is a natural pollutant in wastewater and removal technique such as ammonia electro‐oxidation is of paramount importance. The development of highly efficient and low‐costing electrocatalysts for the ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) associated with ammonia removal is subsequently crucial. In this study, for the first time, the authors demonstrate that a perovskite oxide LaNi0.5Cu0.5O3‐δ after being annealed in Ar (LNCO55‐Ar), is an excellent non‐noble bifunctional catalyst towards both AOR and HER, making it suitable as a symmetric ammonia electrolyser (SAE) in alkaline medium. In contrast, the LNCO55 sample fired in air (LNCO55‐Air) is inactive towards AOR and shows very poor HER activity. Through combined experimental results and theoretical calculations, it is found that the superior AOR and HER activities are attributed to the increased active sites, the introduction of oxygen vacancies, the synergistic effect of B‐site cations and the different active sites in LNCO55‐Ar. At 1.23 V, the assembled SAE demonstrates ≈100% removal efficiency in 2210 ppm ammonia solution and >70% in real landfill leachate. This work opens the door for developments towards bifunctional catalysts, and also takes a profound step towards the development of low‐costing and simple device configuration for ammonia electrolysers., A non‐noble perovskite electrocatalyst, efficiently catalyzing both AOR and HER under alkaline conditions, is identified. The assembled symmetric ammonia electrolyzer based on this bifunctional catalyst delivers the ammonia removal efficiency of ≈100% in ammonia solution and over 70% in a real landfill leachate, demonstrating the huge potential for development of low‐cost and simple configuration for ammonia electrolyzer.

Through Pechini method, a single phase shuttle-shaped perovskite oxide SrFe 0.8 Cu 0.1 Nb 0.1 O 3 − δ was successfully synthesised at 1000 °C. It was combined with active carbon, forming a composite electrode to be used as cathode in a room temperature ammonia fuel cell based on an alkaline membrane electrolyte and Pt/C anode. Reasonable OCV and power density were observed for an ammonia fuel cell using SrFe 0.8 Cu 0.1 Nb 0.1 O 3 − δ /C composite cathode. Although the power density is not high enough for conventional portable or transport applications, it has the potential for stationary application in removal of ammonia from wastewater because the requirements on power density is relatively low. When a dilute 0.02 M ammonia solution (340 ppm) was used as the fuel, the fuel cell using this perovskite oxide can obtain an open circuit voltage of 0.35 V and a power density of 0.03 mW/cm2. In order to obtain higher OCV, NaOH is necessary to be added in the fuel, especially when the fuel contains a low concentration of ammonia. This study indicates that perovskite oxides are potential good cathode for low temperature direct ammonia or alkaline membrane fuel cells.

3D printing of functional energy storage devices is receiving escalating attention over the years due to the customizable manufacturing flexibility and imparted high areal and gravimetric energy density of three-dimensional structured devices, which contribute to the creation of numerous new opportunities for futuristic electronics. Graphene-based inks are ideal elements for the realization of 3D printed energy storage devices if the attractive intrinsic physiochemical properties of graphene could be preserved. However, it is still a great challenge to prepare uniformly dispersed graphene-based materials with desired rheological properties for 3D printing. Here we report a facile strategy for 3D printing of supercapacitors from a highly concentrated graphene oxide (GO) ink. The GO is properly dispersed and the ink fulfills the stringent rheological specifications for 3D printing. The printed GO electrode is functionalized with enhanced structural stability for proper reduction to graphene. The printed supercapacitors deliver the potential to linearly scale up in areal capacitance without jeopardizing the gravimetric capacitance when increasing printed layers. The results hold great promise for the construction of 3D structured energy storage devices that cater to the challenges from next-generation electronics. Keywords: 3D printing, Graphene, Functional ink, Supercapacitor

Single-phase perovskite oxide SrCo0.8 Cu0.1 Nb0.1 O3-δ was synthesized using a Pechini method. X-ray diffraction (XRD) analysis indicated a cubic structure with a=3.8806(7) A. The oxide material was combined with active carbon, forming a composite electrode to be used as the cathode in a room temperature ammonia fuel cell based on an anion membrane electrolyte and NiCu/C anode. An open circuit voltage (OCV) of 0.19 V was observed with dilute 0.02 m (340 ppm) ammonia solution as the fuel. The power density and OCV were improved upon the addition of 1 m NaOH to the fuel, suggesting that the addition of NaOH, which could be achieved through the introduction of alkaline waste to the fuel stream, could improve performance when wastewater is used as the fuel. It was found that the SrCo0.8 Cu0.1 Nb0.1 O3-δ cathode was converted from irregular shape into shuttle-shape during the fuel cell measurements. As the key catalysts for electrode materials for this fuel cell are all inexpensive, after further development, this could be a promising technology for removal of ammonia from wastewater.

Graphitic carbon materials have shown great potential for use as high-performance catalysts for electrochemical reactions and devices. In this work, we developed a simple and versatile method for synthesis of porous N-doped graphene layers (NGS) by high-temperature treatment of chitosan film deposited on the graphitic carbon nitride (g-C 3 N 4 ) nanosheets. In the sandwiched chitosan/g-C 3 N 4 /chitosan structure, the g-C 3 N 4 nanosheet served as a substrate for chitosan film. The pyrolysis of this substrate, g-C 3 N 4 nanosheet, prevented the severe agglomeration of as-carbonized chitosan sheets and resulted the porous structure. The BET surface area, micropore volume, nitrogen content and graphitic level of result sample highly depended on the heat-treatment temperature. The NGS synthesized at 1000 °C (NGS-1000) exhibited an ultrahigh specific surface area (1183 m 2 g −1 ) and high nitrogen content (4.12%). Importantly, NGS-1000 exhibited a higher limiting current density (5.8 mA cm −2 ) and a greater stability than the commercial Pt/C electrocatalyst in alkaline media for oxygen reduction reaction (ORR). Such excellent electrocatalytic performance can be explained by a balanced combination of appropriate nitrogen doping level, the degree of graphitization, porous structure, and high specific surface area.

For the first time, new Sm doped cerium oxynitrides with the formula Ce1-zSmzO2-xNy (z ≤ 0.5) are synthesized in order to maximize the concentration of anion vacancies. Single phase Sm-doped CeO2-xNy were confirmed by XRD, HRTEM and Rietveld refinement. These oxynitrides show a great promotion effect for the low-cost Fe catalyst for the ammonia synthesis. At 350 °C and 1 MPa, the activity of 80 wt% Fe- 20 wt% Ce1-zSmzO2xNy is one of the highest reported for non-Ru catalysts for the Haber-Bosch reaction. The apparent activation energy of the 80 wt% Fe- 20 wt% Ce1-zSmzO2xNy catalysts with z ≥ 0.3 is around 45 kJ/mol, which is in the lowest range among all reported ammonia synthesis catalysts. Introduction of nitrogen vacancies through doping may facilitate the mobility of nitrogen vacancies. This study demonstrates doped oxynitrides with a large concentration of anion vacancies, particularly nitrogen vacancies are excellent promoters/co-catalysts for ammonia synthesis.

Due to its essential use as a fertilizer, ammonia synthesis from nitrogen and hydrogen is considered to be one of the most important chemical processes of the last 100 years. Since then, an enormous amount of work has been undertaken to investigate and develop effective catalysts for this process. Although the catalytic synthesis of ammonia has been extensively studied in the last century, many new catalysts are still currently being developed to reduce the operating temperature and pressure of the process and to improve the conversion of reactants to ammonia. New catalysts for the Haber–Bosch process are the key to achieving green ammonia production in the foreseeable future. Herein, the history of ammonia synthesis catalyst development is briefly described as well as recent progress in catalyst development with the aim of building an overview of the current state of ammonia synthesis catalysts for the Haber–Bosch process. The new emerging ammonia synthesis catalysts, including electride, hydride, amide, perovskite oxide hydride/oxynitride hydride, nitride, and oxide promoted metals such as Fe, Co, and Ni, are promising alternatives to the conventional fused‐Fe and promoted‐Ru catalysts for existing ammonia synthesis plants and future distributed green ammonia synthesis based on the Haber–Bosch process.

Aqueous rechargeable Zn/MnO2 batteries are attractive due to their low-cost, high safety and use of non-toxic materials. In term of electrolyte materials, it is anticipated that an aqueous electrolyte with a wider electrochemical window will improve the stability and energy density. In this work, we investigated salt-concentrated electrolytes based on relatively inexpensive acetate salts. An electrochemical window of 3.4 ​V was achieved in salt-concentrated 1 ​m Zn(OAc)2+31 ​m KOAc electrolyte. Its total ionic conductivity is 2.96 ​× ​10-2 ​S ​cm-1 while the ionic conductivity of Zn2+ ions is 7.80 ​× ​10-3 ​S ​cm-1, estimated by a current interrupt method. This electrolyte is regarded as a mild alkaline environment with a pH value of 9.76, causing the different storage mechanism for anode with Zn2+ ions and, cathode with OH- ions as the charge carriers respectively. A Zn/MnO2 battery was assembled using 1 ​m Zn(OAc)2+31 ​m KOAc electrolyte, self-supported α-MnO2-TiN/TiO2 cathode and Zn foil anode. The Zn/MnO2 battery can be charged to 2.0 ​V versus Zn/Zn2+ and delivers discharge capacity and energy density of 304.6 ​mAh·g-1 (calculated on the mass of MnO2) or 0.32 mAh·cm-2 (calculated on the area of electrode) and, 368.5 ​Wh·kg-1 (calculated on the mass of MnO2) or 232.7 Wh·kg-1 (calculated on the total active mass of electrodes and electrolyte) in the first cycle under a current density of 100 mA·g-1 (~ C/3, based on the mass of MnO2) or 0.1 mA·cm-2 (based on the area of electrode). During cycling, the coulombic efficiency can be maintained around 99% and reached 99.9% during the 14-340th cycles. After the cycling tests, almost no dendrites were observed on the Zn foil anode attributing to the super-high salt concentration in that acetate-based electrolyte, which will benefit the stability of aqueous Zn/MnO2 batteries.

In this work, for the first time, an “oversaturated gel electrolyte” (OSGE) with extended electrochemical windows for use as electrolytes in aqueous batteries was investigated. The stability window of the 10 m LiClO4–PVA OSGE is 3.3 V when saturated at 95 °C, which is 0.6 V wider than the 2.7 V for the 6 m (saturated at room temperature) LiClO4–PVA electrolyte. The ionic conductivity of 10 m LiClO4–PVA OSGE is 1.32 × 10–2 S·cm–1 at room temperature. Zn(ClO4)2 is further added to LiClO4–PVA OSGE to introduce Zn2+ ion conduction, which is optimized to 1 m Zn(ClO4)2 + 10 m LiClO4–PVA and applied as the electrolyte in aqueous rechargeable Zn–Li hybrid batteries. The conductivity of Zn2+ ions is estimated as 5.31 × 10–3 S·cm–1 in the 1 m Zn(ClO4)2 + 10 m LiClO4–PVA OSGE, which is high enough for this OSGE to be used as an electrolyte for batteries using Zn2+ ions as the charge carriers. The quasi-solid-state hybrid battery reaches a voltage of 2 V and delivers its highest discharge capacity and energy density as 116.6 mAh·g–1 and 183.3 Wh·kg–1 (calculated on the 5.6 mg active mass of LiMn2O4), respectively, at first cycle, becoming 93.5 mAh·g–1 and 138.0 Wh·kg–1 after 300 cycles with nearly 100% Coulombic efficiency for the first 30 cycles before then becoming about 99% Coulombic efficiency in the following cycles. OSGE is a useful strategy to develop aqueous electrolytes with wide electrochemical stability windows that can bed used for electrochemical devices.\ud \ud

This work was financially supported by the Australian Research Council under the Discovery Project Scheme (project numbers: DP180100731 and DP180100568), and by the Guangdong Provincial Department of Science and Technology Agency (GDST) under the GDST-NOW Science-Industry Cooperation Program (No. 2017A050501053). The establishment of intimate electrode/electrolyte interface is very important in solid oxide fuel cells (SOFCs), because it plays a critical role in the overall cell performance and durability. In this study, Mn segregation and interface formation between directly assembled La0.8Sr0.2MnO3 (LSM) electrode and yttrium-stabilized zirconia (YSZ) or gadolinium-doped ceria (GDC) electrolytes are studied using combined focused ion beam and scanning transmission electron microscopy (FIB-STEM). In the case of LSM/YSZ and LSM/GDC electrodes, a significant reduction in the electrode ohmic resistance is observed after cathodic polarization at 900 °C and 500 mA cm−2, indicating the formation of an intimate interface. However, LSM particles start to disintegrate at the electrode/electrolyte interface with the increase of polarization time in the case of LSM/YSZ electrode. On the other hand, the LSM/GDC interface is very stable with negligible microstructure change at the interface. Mn segregation from the LSM perovskite structure is identified under the influence of polarization in both LSM/YSZ and LSM/GDC electrodes. The results demonstrate that nature of the electrolyte plays a critical role in the electrochemical activity, microstructure, morphology and stability of LSM/electrolyte interface under SOFC operation conditions. Postprint

In this work, nanoporous nickel-copper sulfide on carbon cloth was successfully prepared via sulfurizing the nickel-copper carbonate hydroxide precursor through an anion exchange reaction. The as-fabricated electrode exhibits a high specific capacitance of 938.6 F g−1 at a current density of 1 A g−1 and good rate capability of 76% at 10 A g−1, as well as excellent flexibility. Charge storage analysis demonstrates that the combination of surface-controlled capacitive process and diffusion-controlled Faradaic process, both contribute to the total capacitance. In addition, the good performance of the nanoporous nickel-copper sulfide can be attributed to the possible higher conductivity and porous nanostructures which offers more active sites to yield extrinsic pseudocapacitance. A hybrid supercapacitor was assembled with nickel-copper sulfide as the positive electrode and nitrogen-doped graphene as the negative electrode, delivering a high cell voltage up to 1.7 V with a maximum energy density of 35.3 Wh kg−1 and a maximum power density of 12700 W kg−1. A red round light-emitting diode (LED) was successfully illuminated by the pouch cell composed of two Ni0.8Cu0.2−S//NG HSCs. The high performance we achieved suggests that the nanoporous nickel-copper sulfide has deep potential for high-performance supercapacitor applications.

As a convenient preparation technique, a two-step method, which is normally done by spin-coating CH3NH3I onto PbI2 film followed by a thermal annealing, is generally used to prepare solution-processed CH3NH3PbI3 films for planar perovskite solar cells. Here, we prepare the compact CH3NH3PbI3 thin films by the two-step method at a low temperature (

One of the most attractive routes for the production of hydrogen or syngas for use in fuel cell applications is the reforming and partial oxidation of hydrocarbons. The use of hydrocarbons in high temperature fuel cells is achieved through either external or internal reforming. Reforming and partial oxidation catalysis to convert hydrocarbons to hydrogen rich syngas plays an important role in fuel processing technology. The current research in the area of reforming and partial oxidation of methane, methanol and ethanol includes catalysts for reforming and oxidation, methods of catalyst synthesis, and the effective utilization of fuel for both external and internal reforming processes. In this paper the recent progress in these areas of research is reviewed along with the reforming of liquid hydrocarbons, from this an overview of the current best performing catalysts for the reforming and partial oxidizing of hydrocarbons for hydrogen production is summarized.

A catalytic material is introduced into the polymer matrix to prepare a novel polymeric alkaline electrolyte membrane (AEM) which simultaneously increases ionic conductivity, reduces the fuel cross-over. In this work, the hydroxide anion exchange membrane is mainly composed of poly(vinylalcohol) and alkaline exchange resin. CoCl2 is added into the poly(vinylalcohol) and alkaline exchange resin gel before casting the membrane to introduce catalytic materials. CoCl2 is converted into CoOOH after the reaction with KOH solution. The crystallinity of the polymer matrix decreases and the ionic conductivity of the composite membrane is notably improved by the introduction of Co-species. A direct borohydride fuel cell using the composite membrane exhibits an open circuit voltage of 1.11 V at 30 °C, which is notably higher than that of cells using other AEMs. The cell using the composite membrane achieves a maximum power density of 283 mW cm−2 at 60 °C while the cell using the membrane without Co-species only reaches 117 mW cm−2 at the same conditions. The outstanding performance of the cell using the composite membrane benefits from impregnation of the catalytic Co-species in the membrane, which not only increases the ionic conductivity but also reduces electrode polarization thus improves the fuel cell performance. This work provides a new approach to develop high-performance fuel cells through adding catalysts in the electrolyte membrane.

Ammonia is an attractive carbon-free chemical for electrochemical energy conversion and storage. However, the sluggish kinetic rates of the ammonia electrooxidation reaction, and high cost and poisoning of Pt-based catalysts still remain challenges. This also limits the development of direct ammonia fuel cells. In this work, we directly grew hierarchical mixed NiCu layered hydroxides (LHs) nanowires on carbon fibre cloth electrodes by a facile one-step hydrothermal synthesis method for efficient electro-oxidation of ammonia. This catalyst achieves a current density of 35 mA cm−2 at 0.55 V vs. Ag/AgCl, which is much higher than that of bare Ni(OH)2 catalyst (5 mA cm−2). This is due to abundant active sites and a synergistic effect between Ni and Cu, possibly due to the formation of Ni1−xCuxOOH on the surface of the catalysts through the electrochemical activation of the mixture of Cu(OH)2 and α-Ni(OH)2. In the investigated first row transition elements, it is found that Cu is the sole first-row transition metal to effectively improve activity of Ni(OH)2 for ammonia electrooxidation. This mixed NiCu LHs nano-wire catalyst outperforms commercial Pt/C catalyst in the aspects of ammonia oxidation current and stability, demonstrating it to be a promising low-cost and stable catalyst for efficient ammonia electrooxidation in alkaline condition, which is a potential electrode for ammonia fuel cells for power generation or electrolysis of ammonia for ammonia-containing wastewater treatment.\ud \ud

A La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ -Ce 0.8 Gd 0.18 Ca 0.02 O 2−δ composite cathode was used to investigate the electrochemical synthesis of ammonia from wet nitrogen. Wet nitrogen was flown through a dual chamber reactor under atmospheric pressure leading to the successful synthesis of ammonia. Ammonia was synthesised at a rate of 1.5 × 10 −10 mol s −1 cm −2 at 400 °C when applying a dc voltage of 1.4 V, which is the highest reported to date. This rate is twice that of the observed ammonia formation rate (7 × 10 −11 mol s −1 cm −2 ) when Co-free cathode, La 0.6 Sr 0.4 FeO 3−δ -Ce 0.8 Gd 0.18 Ca 0.02 O 2−δ was used as the cathode catalyst. A higher catalytic activity for ammonia synthesis may be obtained when using a catalyst with high oxygen vacancies, with the introduction of oxygen vacancies at the cathode being a good strategy to improve the catalytic activity of ammonia synthesis.

As a greenhouse gas, carbon dioxide in the atmosphere is one of the key contributors to climate change. Many strategies have been proposed to address this issue, such as CO2 capture and sequestration (CCS) and CO2 utilization (CCU). Electroreduction of CO2 into useful fuels is proving to be a promising technology as it not only consumes CO2 but can also store the redundant electrical energy generated from renewable energy sources (e.g., solar, wind, geothermal, wave, etc.) as chemical energy in the produced chemicals. Among all of products from CO2 electroconversion, formic acid is one of the highest value-added chemicals, which is economically feasible for large-scale applications. This paper summarizes the work on inorganic cathode catalysts for the electrochemical reduction of CO2 to formic acid or formate. The reported metal and oxide cathode catalysts are discussed in detail according to their performance including current density, Faradaic efficiency, and working potentials. In addition, the effects of electrolyte, temperature, and pressure are also analyzed. The electroreduction of CO2 to formic acid or formate is still at an early stage with several key challenges that need to be addressed before commercialization. The major challenges and the future directions for developing new electrocatalysts for the reduction of CO2 to formic acid are discussed in this review.

New perovskite oxides SrFe0.7TM0.2Ti0.1O3-δ (TM = Mn, Fe, Co, Ni, Cu) were synthesised by sol-gel processes. Their redox stability and conductivity in both air and 5%H2/Ar were investigated in details. The cubic perovskite structure was also observed for all dopants with variation in the lattice parameters associated with different dopant environments and charge compensation mechanisms. Improvement of the electronic conductivity over SrFe0.9Ti0.1O3-δ was observed for all dopants in air, attributed to increasing charge carrier concentrations. Reduction in 5% H2/Ar exhibited minimal a material properties for SrFe0.7Cu0.2Ti0.1O3-δ, with a significant reduction in conductivity was observed for SrFe0.7Mn0.2Ti0.1O3-δ. All doped compounds exhibited a single phase cubic perovskite structure after reduction in 5%H2/Ar at 700 °C with the exception of SrFe0.7Ni0.2Ti0.1O3-δ and SrFe0.7Co0.2Ti0.1O3-δ which displays secondary nickel and cobalt phases respectively upon reduction. SrFe0.7Cu0.2Ti0.1O3-δ is redox stable at a temperature below 700 °C and highly conductive with conductivities around 10 S cm− 1 in both air and reducing atmosphere which are about five times higher than those of pure SrFe0.9Ti0.1O3-δ. In terms of conductivity and redox stability, it is a potential redox stable electrode material for reversible and symmetrical solid oxide fuel cells as well.\ud \ud

In this work, perovskite Sr1−xPrxFeO3-δ (SPF) (x = 0.02, 0.04, 0.06, 0.08 and 0.10) are investigated and employed as solid oxide steam electrolyser cathode at 800 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM) analysis together indicate that the Sr1−xPrxFeO3-δ is redox reversible with a phase transition from cubic to orthorhombic structure in redox cycles. The doping of Pr in A site has remarkably enhanced the electronic conduction to 1.0–1.2 S cm−1 at intermediate temperatures in reducing atmosphere. Electrochemical measurements demonstrate that the polarization resistance with Sr0.96Pr0.04FeO3-δ electrode shows the lowest values of 0.25 Ω cm2 in symmetric cells in reducing atmosphere at 800 °C. Direct steam electrolysis with Sr0.96Pr0.04FeO3-δ cathode shows a current density of 1.64 A cm−2 at 2.0 V when fed with 5%H2O/Ar. The hydrogen production rate reaches 4.73, 6.68, 8.35 and 10.23 mL min−1 cm−2 at 1.4, 1.6, 1.8, 2.0 V, respectively, while the highest Faraday efficiency is as high as 97.16% at 1.8 V.

Perovskite oxide (La,Sr)TiO3+δ (LSTO) cathode has demonstrated promising performance for direct CO2 electrolysis due to its unique redox-stable properties. However, insufficient electro-catalytic activity of titanate remains a major drawback that limits electrode performance. In this paper, catalytically active scandium is doped to LSTO to enhance cathode performances. The structure, electronic conductivity and ionic conductivity of La0.2Sr0.8Ti1−xScxO3+δ (LSTSxO) (x = 0, 0.05 and 0.1) are investigated and further correlated with electrode performances. XRD, TEM, TGA and XPS indicate the successful partial replacement of Ti by Sc in the B site of titanate. The improved electrode performances are strongly dependent on scandium doping contents. Promising direct CO2 electrolysis performance is demonstrated with near 100% current efficiency based on La0.2Sr0.8Ti0.9Sc0.1O3+δ at 1.7 V and 800 °C.

Urea is a safe and sustainable chemical for electrochemical energy conversion and storage. However, the sluggish kinetic rates of the electrooxidation reaction of urea as well as catalyst stability still remain to be challenges. In this work, we investigated several catalysts for the electro-oxidation of urea by directly growing NiM double hydroxides (M = Cr, Mn, Fe, Co, Cu, Zn) on carbon fibre cloth and nickel foam electrodes through a facile one-step hydrothermal synthesis method. The results indicated that the activity was significantly related to the elemental composition. Among the investigated double hydroxides, the NiFe double hydroxide (DH) catalyst showed the highest activity, which achieved a specific current density of ∼95 mA cm−2 mg−1 at 0.5 V vs. Ag/AgCl, about 10 times larger than that of Ni(OH)2. In addition, the NiFe DH also had a high activity when grown on a Ni foam substrate. This NiFe DH performs well in the aspect of urea oxidation stability, demonstrating it to be a promising low-cost and stable catalyst for the efficient electrooxidation of urea under alkaline conditions.

Photovoltaic conversion of solar energy into electricity is an alternative way to use renewable energy for sustainable energy production. The great demand of low-cost and efficient solar cells inspires research on solution-processable light-harvesting materials. Antimony trisulfide (Sb2S3) is a promising light-harvester for photovoltaic purposes. Here we report on the in situ grown monolayer of preferentially oriented, large Sb2S3 single-crystalline cuboids on a polycrystalline titania (TiO2) nanoparticle film. A facile, oriented seed-assisted solution-processing method is used, providing the Sb2S3/TiO2-based bulk/nano-planar heterojunction with a preferred structure for efficient planar solar cells. An orientation-competing-epitaxial nucleation/growth mechanism is proposed for understanding the growth of the Sb2S3 single-crystalline cuboids. With an organic hole transporting material, the stable solar cell of the heterojunction yields a power conversion efficiency of 5.15% (certified as 5.12%). It is found that the [221]-oriented Sb2S3 cuboids provide highly effective charge transport channels inside the Sb2S3 layer.

Currently, low catalytic activity, selectivity and stability are the biggest challenges which restrict the large scale applications of CO2 electrochemical reduction. Formic acid, one of the highest value-added products from electrochemical reduction of CO2, has gathered much interest. Here, we develop nanoporous tin foam catalysts which exhibit significantly high selectivity and faster production rate to formate. In a 0.1 M NaHCO3 solution, the maximum Faradaic efficiency for formate production reaches above 90% with a current density over 23 mA cm-2 , which are among the highest reported value to date under ambient conditions. The improved production rate can be attributed to the high surface area and porous structure. Moreover, the electrocatalysts are quite stable, namely, the Faradaic efficiency remains unchanged during 16 hour electrolysis. This is a promising technology to convert CO2 into useful hydrocarbons.

A series of new perovskite oxides Sr1.6K0.4Fe1+x Mo1−x O6−δ (x = 0.2, 0.4, 0.6) were synthesised by solid state reaction method. Synthesis of Sr1.6K0.4Fe1+x Mo1−x O6−δ (x = 0.2, 0.4, 0.6) was achieved above 700 °C in 5 % H2/Ar, albeit with the formation of impurity phases. Phase stability upon redox cycling was only observed for sample Sr1.6K0.4Fe1.4Mo0.6O6−δ. Redox cycling of Sr1.6K0.4Fe1+x Mo1−x O6−δ (x = 0.2, 0.4, 0.6) demonstrates a strong dependence on high temperature reduction to achieve high conductivities. After the initial reduction at 1200 °C in 5 %H2/Ar, then re-oxidation in air at 700 °C and further reduction at 700 °C in 5 %H2/Ar, the attained conductivities were between 0.1 and 58.4 % of the initial conductivity after reduction 1200 °C in 5 %H2/Ar depending on the composition. In the investigated new oxides, sample Sr1.6K0.4Fe1.4Mo0.6O6−δ is most redox stable also retains reasonably high electrical conductivity, ~70 S/cm after reduction at 1200 °C and 2–3 S/cm after redox cycling at 700 °C, indicating it is a potential anode for SOFCs.