Impact of the annealing temperature on Pt/g-C3N4 structure, activity and selectivity between photodegradation and water splitting

Acknowledgements: The authors would like to thank SABIC as well as EPSRC platform grant [EP/K015540/1] for financial support and the Royal Society of Chemistry for a Wolfson Merit Award. In order to protect intellectual property the data underpinning this publication are not made publicly available. All enquiries about the data should be addressed to [email protected] reviewedPostprin

Non-stoichiometry, structure and properties of proton-conducting perovskite oxides

We appreciate that EPSRC-EP/P007821/1 and LERG for funding support.The demand for clean and sustainable energy has garnered great interest in new energy materials. Among them, high temperature proton-conducting perovskite oxides are, or can be widely used in clean energy applications (including fuel cells, electrochemical reactors, solid-state separators and supports of catalytic components via various reduction and oxidation reactions) in the intermediate temperature range. The control of defect chemistry is the main strategy to fine tune properties for these applications. This review provides a critical discussion about non-stoichiometry-structure-property relation in terms of structure distortions by intrinsic octahedral titling and extrinsic acceptor doping, chemical stability, hydration behavior, transport properties, and catalytic effects in some typical classes of proton conducting perovskites and perovskite-related derivatives. A good understanding of A-site and B-site non-stoichiometry is also given to allow the perovskite structure with desired properties.PostprintPeer reviewe

Synthesis of ammonia directly from air and water at ambient temperature and pressure

The N≡N bond (225 kcal mol−1) in dinitrogen is one of the strongest bonds in chemistry therefore artificial synthesis of ammonia under mild conditions is a significant challenge. Based on current knowledge, only bacteria and some plants can synthesise ammonia from air and water at ambient temperature and pressure. Here, for the first time, we report artificial ammonia synthesis bypassing N2 separation and H2 production stages. A maximum ammonia production rate of 1.14 × 10−5 mol m−2 s−1 has been achieved when a voltage of 1.6 V was applied. Potentially this can provide an alternative route for the mass production of the basic chemical ammonia under mild conditions. Considering climate change and the depletion of fossil fuels used for synthesis of ammonia by conventional methods, this is a renewable and sustainable chemical synthesis process for future

Oxygen storage capacity and thermal stability of brownmillerite-type Ca2(Al1-xGax)MnO5+δ oxides

The authors gratefully thank the National Natural Science Foundation of China (No. 51802015), and the Engineering and Physical Sciences Research Council platform grant (EP/I022570/1 and EP/I022570/2) for financial support.Understanding the oxygen uptake/release mechanism in oxygen storage materials is of great importance in the design of energy-related materials and their corresponding applications. In this work, the effects of Ga doping amount on the oxygen storage capacity and thermal stability of Ca2(Al1-xGax)MnO5+δ (0 ≤ x ≤ 1) with a brownmillerite-type structure were investigated. Ca2AlMnO5+δ can reversibly store/release a large amount of excess oxygen (∼3.0 wt%) at low temperature (between 300 and 600 °C) under oxidative atmospheres. With the increasing Ga doping amount in Ca2(Al1-xGax)MnO5+δ, these materials uptake less oxygen at higher temperature which can be attributed to the difficulty in the oxidation of tetrahedral GaO4 blocks into octahedral GaO6 blocks under 1 atm O2. However, with the increasing of Ga-substitution amount, these Ca2(Al1-xGax)MnO5+δ (0 ≤ x < 1) can start to uptake oxygen at lower temperatures during the cooling process under flowing O2 due to the distorted structure. The results demonstrated that Ca2(Al1-xGax)MnO5+δ (0 ≤ x < 1) can reversibly store/release large amounts of oxygen via just controlling the surrounding temperature and/or oxygen partial pressure but without using reductive gases, which would enable them great potentials in many applications.PostprintPeer reviewe

Half-cell study of La and Ca doped strontium titanates anode for direct methane solid oxide fuel cell

One of the major advantages of Solid oxide fuel cell (SOFC) over other fuel cell is use of direct natural gas at high temperature without any external reformer. Conventional nickel-yttria stabilized zirconia (Ni-YSZ) composite anode provides excellent catalytic property, current collection and stability for H2 oxidation but it is not tolerant towards sulphur poisoning and also accelerates coke deposition in presence of methane fuel. It necessitates the use of alternate anode for direct hydrocarbon fuel. In the present work, attempts have been made to apply La and Ca doped A-site deficient SrTiO3 (LSCTA-) as potential anode for direct methane SOFC. Low catalytic activity of LSCTA- is improved by infiltration of Ni and CeO2 catalyst. Half cell (YSZ/4%Ni-6%CeO2-LSCTA-) provided 200 mW cm-2 maximum power density and regain its initial performance in H2 even after 6 h exposure to humidified CH4 at 800 °C.Postprin

La and Ca-doped A-site deficient strontium titanates anode for electrolyte supported direct methane solid oxide fuel cell

The authors thank UKIERI and DST for financial help during execution of the project.Nickel-yttria stabilized zirconia (Ni-YSZ) cermet anodes for solid oxide fuel cells (SOFC) possesses excellent catalytic properties and stability for H2 oxidation but not for hydrocarbons as it results in fast carbon deposition in absence of excess steam. In the present work, A-site deficient porous LSCTA- (La0.2Sr0.25Ca0.45TiO3) anode has been fabricated using the environment friendly, aqueous tape casting method followed by the same procedure for the dense YSZ electrolyte and YSZ porous scaffold as cathode matrix. The anode, electrolyte, and porous cathode matrix have been laminated together and sintered up to 1350°C. After sintering, nitrate precursors of La, Sr, Co and Fe are infiltrated inside the porous YSZ cathode matrix to form the perovskite phases of La0.8Sr0.2CoO3 (LSC) and La0.8Sr0.2FeO3 (LSF). The as fabricated electrolyte supported SOFCs have been tested in H2 and CH4 fuel at 800°C. The electrolyte supported cell 15%LSF-5% LSC-YSZ/YSZ/4%Ni-6%CeO2-LSCTA- gives maximum power density of 328 mW cm−2 for 3 h in H2, but in CH4 the performance decreased to 165 mW cm−2 even though a sustained open circuit voltage of ∼1 V obtained during H2 and CH4 operation. The morphology of the anode before and after cell testing has been analyzed using scanning electron microscope followed by X-ray diffraction studies to understand phase changes during fabrication and testing.PostprintPeer reviewe

Inorganic perovskite photocatalysts for solar energy utilization

The authors acknowledge funding from the Engineering and Physical Research Council for research award EP/K036769/1 and Platform Grant EP/K015540/1. Financial support from the Major Basic Research Program, Ministry of Science and Technology of China (2014CB239401) and the NSFC (51422210, 51629201) is acknowledged. The authors also acknowledge support from The Royal Society Newton Fellowship, NA140077 and The Royal Society Wolfson Merit Award, WRM 2012/R2.The development and utilization of solar energy in environmental remediation and water splitting is being intensively studied worldwide. During the past few decades, tremendous efforts have been devoted to developing non-toxic, low-cost, efficient and stable photocatalysts for water splitting and environmental remediation. To date, several hundreds of photocatalysts mainly based on metal oxides, sulfides and (oxy)nitrides with different structures and compositions have been reported. Among them, perovskite oxides and their derivatives (layered perovskite oxides) comprise a large family of semiconductor photocatalysts because of their structural simplicity and flexibility. This review specifically focuses on the general background of perovskite and its related materials, summarizes the recent development of perovskite photocatalysts and their applications in water splitting and environmental remediation, discusses the theoretical modelling and calculation of perovskite photocatalysts and presents the key challenges and perspectives on the research of perovskite photocatalysts.PostprintPostprintPeer reviewe

Computational screening of anode coatings for garnet-type solid-state batteries

Funding: C. L. thanks the Chinese Scholarship Council for funding. M. B. acknowledges support by the School of Chemistry and EaStCHEM. We also acknowledge support from The Faraday Institution Grant (FIRG031), New Approaches to processing of oxide solid state batteries.Making use of a large materials database of DFT-derived structures and energies, we applied a high-throughput computational screening framework to identify Li-containing oxides as potential anode coatings for lithium garnet. A preselection of candidate materials was made based on their phase stability, electrochemical stability, and chemical stability, as emerging from this database. Then first-principles calculations (periodic DFT calculations at the PBE level) were performed to further evaluate the Li-ion conductivity and Li wettability of these coatings. A total of 10 Li-M-O compounds (Li3BO3, LiAlO2, Li5AlO4, Li4SiO4, Li8SiO6, Li4TiO4, Li8TiO6, Li6Zr2O7, Li2HfO3 and Li6Hf2O7) were identified as the most promising anode coatings. According to our findings, lithium concentration can affect the desired electrochemical stability and Li wettability in an opposing way. Compounds with high Li content tend to have low reduction potential with poor lithium wettability. Target materials may have a "sweet spot" in terms of Li content, where all key properties are balanced in an optimal way.Publisher PDFPeer reviewe

Geometric frustration and concerted migration in the superionic conductor barium hydride

Authors would like to thank the ISIS Facility Development Studentship for funding this work. Additionally, I would like to thank ISIS Neutron and Muon Source for providing the beam time to collect all the scattering data presented in this paper. Finally, I would like to thank the Crockett Scholarship for supporting my studies. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) license to any Accepted Author Manuscript version arising.Ionic conductivity is a phenomenon of great interest, not least because of its application in advanced electrochemical devices such as batteries and fuel cells. While lithium, sodium, and oxide fast ion conductors have been the subjects of much study, the advent of hydride (H–) ion fast conductors opens up new windows in the understanding of fast ion conduction due to the fundamental simplicity of the H– ion consisting of just two electrons and one proton. Here we probe the nature of fast ion conduction in the hydride ion conductor, barium hydride (BaH2). Unusually for a fast ion conductor, this material has a structure based upon a close-packed hexagonal lattice, with important analogues such as BaF2 and Li2S. We elucidate how the structure of the high temperature phase of BaH2 results in a disordered hydride sublattice. Furthermore, using novel combined quasi-elastic neutron scattering (QENS) and electrochemical impedance spectroscopy (EIS) we show how the high energy ions interact to create a concerted migration that results in macroscopic superionic conductivity via an interstitialcy mechanism.Publisher PDFPeer reviewe

A new approach to fuel cell electrodes : lanthanum aluminate yielding fine Pt nanoparticle exsolution for oxygen reduction reaction

We acknowledge support from the Engineering and Physical Sciences Research Council (EPSRC) Critical Mass Grant EP/R023522/1, EPSRC Light element Analysis Facility Grant EP/T019298/1 and the EPRC Strategic Equipment Resource grant EP/R023751/1.Designing an electrocatalyst with low Pt content is an immediate need for essential reactions in low temperature fuel cell systems. In the present work, La0.9925Ba0.0075Al0.995Pt0.005O3 is aimed at using with low (only 0.5%) Pt doping as an electrocatalyst for oxygen reduction reaction (ORR). The low doping level renders exsolution of 1–2 nm nanoparticles with uniform dispersion upon reduction in H2/N2 at low temperatures. Pt exsolved perovskite oxides deliver significantly enhanced catalytic activity for ORR and improved stability in alkaline media. This study demonstrates that LaAlO3 with low noble metal content holds immense potential as an electrocatalyst in real fuel cell systems.Peer reviewe