Nanoscale anti-ferromagnetic (AFM) NiO exhibits intriguing magnetic anomalies influenced by factors such as size, stoichiometry, surface chemistry, and lattice strain. In the present work, black-coloured NiO nanoparticles were synthesized by combustion method, incorporating cationic Ni2+ vacancies and Ni3+ species on their surface. Annealing NiO at high temperatures (400–800 °C) led to a colour change from black to green, indicating the transition from a non-stoichiometric to a stoichiometric state. The formation of Ni2+ vacancies disrupted AFM ordering between Ni2+ and O2− ions, while the presence of Ni3+ promoted double exchange interactions between Ni3+ and neighbouring Ni2+ ions, contributing to ferromagnetism (FM) in AFM NiO. The spin exchange interaction at AFM-FM core–shell interface in NiO resulted in an exchange bias effect. Notably, the NiO nanoparticles with smaller average crystallite size ( 5 nm) and higher cationic Ni2+ vacancies on the surface exhibited strong ferromagnetism and higher coercivity values. In particular, the as-prepared NiO (N) and N-4 samples showed remarkable improvement in exchange bias field, measuring 2.5 kOe and 2.1 kOe, respectively, due to the reinforced spin-exchange interaction within the FM-AFM core–shell structure of NiO.

Surplus renewable electricity used to convert CO2 into CO, the building block of liquid fuels, advances the energy transition by enabling large-scale, long-term energy storage and the synthesis of fuel for long-haul transportation. Among the various technologies developed, renewable electricity driven conversion of CO2 by high-temperature electrolysis and by plasmolysis offer a tantalising potential. High-temperature electrolysis is characterized by high-yield and energy-efficiency and the direct separation of the CO2 dissociation products CO and O-2. However, the difficulty to break the carbon-oxygen double bond poses challenging requirements on electrode materials. CO2 plasmolysis on the other hand, offers a similar energy efficiency, does not employ scarce materials, is easy to upscale, but requires efficient gas separation and recuperation because the produced CO remains mixed with O-2 and residual CO2. Here, we demonstrate that the coupling of the two processes leads to a renewable-electricity-driven route for producing CO from CO2, overcoming the main bottleneck of CO2 plasmolysis. A simulated CO2 plasmolysis gas mixture is supplied to a h(i)gh-temperature electrolyser to separate the product gases electrochemically. Our results show that the product stream of the coupled-process contains 91% less oxygen and 138% more CO compared with the bare plasmolysis process. Apart from upgrading the produced gas mixture, this coupled approach benefits from material stability. Durability tests (similar to 100 h) show better stability in coupled operation when compared with conventional CO2 electrolysis. Synergy between plasmolysis and electrolysis opens up a novel route to efficient CO2 conversion into valuable CO feedstock for the synthesis of long-chain hydrocarbons.

Perovskite oxides with dispersed nanoparticles on their surface are considered instrumental in energy conversion and catalytic processes. Redox exsolution is an alternative method to the conventional deposition techniques for directly growing well-dispersed and anchored nanoarchitectures from the oxide support through thermochemical or electrochemical reduction. Herein, a new method for such nanoparticle nucleation through the exposure of the host perovskite to plasma is shown. The applicability of this new method is demonstrated by performing catalytic tests for CO2 hydrogenation over Ni exsolved nanoparticles prepared by either plasma or conventional H2 reduction. Compared to the conventional thermochemical H2 reduction, there are plasma conditions that lead to the exsolution of a more than ten times higher Ni amount from a lanthanum titanate perovskite, which is similar to the reported values of the electrochemical method. Unlike the electrochemical method, however, plasma does not require the integration of the material in an electrochemical cell, and is thus applicable to a wide range of microstructures and physical forms. Additionally, when N2 plasma is employed, the nitrogen species are stripping out oxygen from the perovskite lattice, generating a key chemical intermediate, such as NO, rendering this technology even more appealing.

The higher grain boundary resistance in the proton-conducting yttrium-doped barium zirconate is one of the major issues to be solved. A new strategy has been experimentally studied on the basis of space charge theory to understand the grain boundary resistance in pristine and 20 mol % yttrium-doped barium zirconate by varying the sintering temperature (1200, 1300, 1400, and 1500 °C). The electrical response upon applying a DC bias indicates the existence of space charge in the grain boundary region of barium zirconate. The Mott–Schottky analysis was performed at a lower temperature of 100 °C to infer the information from the grain boundary region. A parabolic reduction in normalized proton concentration was observed from the grain boundary to its core. The barrier height varied in the range of 0.55–0.15 V depending on the sintering temperature. The increase in dopant concentration along the grain boundary resulted in the reduction of barrier height as well as space charge width. Hence, the presence of yttrium and subsequent variation of the sintering temperature have a strong influence on space charge modulation and affect the grain boundary resistance.

By tailoring the nano-column structures of a sputtered Ni anode, the in-plane connectivity of the nanostructured Ni anode is significantly improved.

Recently, new perovskite cathode material, SrCo0.8Nb0.1Ta0.1O3-δ (SCNT) was reported, showing high oxygen reduction reaction (ORR) activity. This study demonstrates thin film deposition of SCNT by pulsed laser deposition technique applied to anodic aluminum oxide (AAO) based thin-film solid oxide fuel cells (TF-SOFCs) to assess the possibility of SCNT application to TF-SOFCs. The SCNT powder and the target were prepared by the solid state reactive sintering method (SSRS). This target was then mounted to the pulsed laser depositing machine and deposited on the Si wafer, and the nano-porous substrate, AAO. The physical structure and the chemical phase were investigated by the field emission scanning electron microscope, focused ion beam scanning electron microscope, and X-ray diffraction. On the top of the AAO, thin Pt film and yttria stabilized zirconia (YSZ) were first deposited by sputtering and the SCNT was deposited on the top of it afterward. The open circuit voltage of AAO cell was tested at 500°C, and successful polarization activity of SCNT was observed.

The carbon dioxide and steam co-electrolysis in solid oxide cells offers an efficient way to store the intermittent renewable electricity in the form of syngas (CO + H-2), which constitutes a key intermediate for the chemical industry. The co-electrolysis process, however, is challenging in terms of materials selection. The cell composites, and particularly the fuel electrode, are required to exhibit adequate stability in redox environments and coking that rules out the conventional Ni cermets. La0.75Sr0.25Cr0.5Mn0.5O3 (LSCrM) perovskite oxides represent a promising alternative solution, but with electrocatalytic activity inferior to the conventional Ni-based cermets. Here, we report on how the electrochemical properties of a state-of-the-art LSCrM electrode can be significantly enhanced by introducing uniformly distributed Pt nanoparticles (18 nm) on its surface via the atomic layer deposition (ALD). At 850 degrees C, Pt nanoparticle deposition resulted in a similar to 62% increase of the syngas production rate during electrolysis mode (at 1.5 V), whereas the power output was improved by similar to 84% at fuel cell mode. Our results exemplify how the powerful ALD approach can be employed to uniformly disperse small amounts (similar to 50 mu g.cm(-2)) of highly active metals to boost the limited electrocatalytic properties of redox stable perovskite fuel electrodes with efficient material utilization.

The defect association modifies the energy barrier for oxygen ion hopping between the vacancies, which is sensitive to the dopant ionic size in the CeO2-delta. Here, the work focuses on the co-dopant strategy of M0.1Sm0.1Ce0.8O2-delta (M = Yb, Gd, Sm, Nd, La) to study the defect association energy, and its subsequent effect on ionic conduction and power density. The electrolyte material with different co-dopants modifies the lattice parameter and bond length of cation-anion, which changes the defect-dopant interactions. Among the tested dopant, Nd0.1Sm0.1Ce0.8O2-delta exhibits the highest ionic conductivity of 34 mS cm1 at 550 ?C, which is nearly 2.3 times higher than the conventional Sm0.2Ce0.8O2-delta. This experimental observation validates the theoretically proposed concept of the balanced defect-dopant interactions at different sites leading to the reduction in defect association enthalpy. The experimental results were rationalized by calculating the defect association enthalpy for the co-doped system using density functional theory via one-cell method. The cell with Nd0.1Sm0.1Ce0.8O2-delta as an electrolyte shows a peak power density of 466 mW cm-2 at 550 ?C, which is twice higher than the cell containing standard Sm0.2Ce0.8O2-delta electrolyte (212 mW cm? 2). The results confirm that Nd0.1Sm0.1Ce0.8O2-delta is the potential electrolyte for low temperature SOFC operation. Superscript/Subscript Available

A non-noble metal-based bimetallic Cu–Ni system for the conversion of 4-nitrophenol and effective recyclability by magnetic retrieval of the catalyst.

We herein report a thin film deposition of perovskite BaCo0.4Fe0.4Zr0.1Y0.1O3-delta (BCFZY) by pulsed laser depositing (PLD) method for the use as a cathode in solid oxide fuel cells (SOFCs). The BCFZY powder was first synthesized via sol-gel method and pelletized to employ it as a target in PLD system. As a result, the PLD-deposited thin BCFZY film showed nano-porous morphology and preferred nano-architecture for cathode of SOFCs. The applicability of the thin film BCFZY to SOFC cathode was even confirmed by fabricating an SOFC with BCFZY cathode and operating it at 500 degrees C, where stable open-circuit voltage of 1.13 V was measured for an hour.

The current study focus on the exchange bias properties of Ni/NiO ferromagnetic-antiferromagnetic nanocomposite by fabricating Ni (FM) using a one-step solution combustion method. The prepared Ni nanoparticles were oxidized at 400 degrees C for different time durations (tau = 3, 6, 12, 24, 48, 72, 96, 120, 144 and 168 h) in the ambient atmosphere to grow NiO (AFM). The X-ray diffraction pattern of the Ni/NiO nanocomposite indicate good crystallinity of the samples. Raman spectroscopy exhibited a short-range magnon excitation around 1400 cm(-1) that indicate the contribution of AFM exchange energy between the Ni2+-O-2(-)-Ni2+ chain in the composites. The presence of Ni and NiO phases were confirmed by room temperature magnetization measurement. For the better understanding of the exchange bias of the Ni/NiO nanocomposite subjected to heat treatment for several hours (0-168 h), zero-field cooled and field cooled M-H and M-T measurements were made. The hysteresis loop shift along the field axis and enhanced coercivity values shows the exchange bias effect in the Ni/NiO structure in the controlled oxidation process. The Ni and NiO interfacial effect and phase fraction have significant effect on the observed exchange bias. Moreover, finite size effects contribution on the antiferromagnetic exchange and spin glass features observed at a temperature of 24 K of the Ni/NiO system contribute to the large exchange bias and enhanced coercivity. (C) 2018 Elsevier B.V. All rights reserved.

High working temperature(≥800 °C) of solid oxide fuel cell(SOFC) causes high cost of balance of plant, long start up time, and low durability. To overcome these barriers, lowering the working temperature of SOFC is one of the most attractive ways and such strategy has been researched through the fabrication of thin electrolyte and developing new perovskite cathode material. Recently, mixed ionic electronic conducting(MIEC) cathode material, SrCo0.8Nb0.1Ta0.1O3-δ (SCNT), has been developed by Li et al. and the SOFC with the cathode showed high performance(1.22W/cm2) at low working temperature (500 °C) with 14µm thick gadolinia doped ceria(GDC) electrolyte[1]. To apply SCNT to SOFC with thin electrolyte(≤1µm), the cathode must be fabricated on the electrolyte without high temperature sintering process(≥1000 °C) because of the weak mechanical strength of thin electrolyte. In this work, pulsed laser deposition(PLD) method was employed for the fabrication of thin film SCNT. PLD has been used widely for perovskite material deposition because of its high preservability of stoichiometric ratio of its original target material. However, the deposition temperature of PLD has a great influence on both physical and chemical structure of the film which means oxygen reaction activity(ORR) of the film also varies as temperature changes. Therefore, thin film SCNT was deposited by PLD at various temperature condition in this work to see the diversity of thin film characteristic for understanding the feasibility of application of SCNT to thin film SOFC (TF-SOFC). Powder and PLD target of SCNT were both prepared by the method Li et al. used, solid state reactive sintering(SSRS). The film was firstly deposited on Si wafer at various temperature (room temp, 500, 600, 700 °C) by PLD. Field emission scanning electron microscope (FE-SEM) and focused ion beam-SEM (FIB-SEM) were used to see the nano-structure of the film and deposition rate. 75mTorr of oxygen atmosphere was enough to make the structure of thin film deposited at room temperature very porous but dense film was observed at the temperature higher than 500 °C. The atomic ratio and crystallinity of each film were identified by X-ray spectroscopy(XPS) and X-ray diffraction(XRD) respectively. Through the understanding the physical and chemical variation of PLD deposited SCNT at different temperature condition, the best PLD deposition condition of SCNT for TF-SOFC was derived. Acknowledgment This work was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea (2012M3A6A7054855) References [1] M. Li et al., “A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °c,” Nat. Commun., vol. 8, no. 5, pp. 1–9, 2017.

With increasing global interest in renewable energy technology given the backdrop of climate change, storage of electrical energy has become particularly relevant. Most sustainable technologies (e.g., wind and solar) produce electricity intermittently. Thus, converting electrical energy and base molecules (i.e., H2O, N2) into energy-rich ones (e.g., H2, NH3) or chemical feedstock (e.g., NO) is of paramount importance. While H2O splitting is compatible with renewable electricity, N2 fixation is currently dominated by thermally activated processes. In this work, we demonstrate an all-electric route for simultaneous NO and H2 production. In our approach, H2O is reduced to H2 in the cathode of a solid oxide electrolyzer while NO is produced in the anode by the reaction of O2– species (transported via the electrolyte) and plasma-activated N2 species. High faradaic efficiencies up to 93% are achieved for NO production at 650 °C, and NO concentration is >1000 times greater than the equilibrium concentration at t...

Hydrogen is an environmentally friendly alternative to conventional fossil fuels and is considered as a renewable energy carrier for meeting the ever-increasing energy demand. Although hydrogen is abundant on earth in the form of compounds such as water, producing molecular hydrogen demands a large amount of energy. A solid oxide electrolysis cell (SOEC) is an electrochemical device which generates hydrogen from various sources. An SOEC uses high temperature (>800°C) to electrolyse water with high efficiency assisted by thermodynamically favoured water splitting that enables large-scale hydrogen production. This review provides a comprehensive overview of the current status in the developments of high-temperature steam electrolysis using a proton- and oxygen-ion-conducting SOEC system for hydrogen production. The present review summarises the detailed approaches for hydrogen production using SOECs, basic principles, challenges in designing hydrogen and oxygen electrodes and electrolytes, and potential solutions to durability issues.

The antioxidant activity of cerium oxide nanoparticles (CNPs) depends on the concentration of oxygen vacancies and Ce3+ active sites. In the present work, we report the impact of 5 mol % trivalent rare-earth-doped (RE3+ = Eu3+, Nd3+, Pr3+, and La3+) CNPs on the oxidation state modulation and antioxidant property with respect to ionic radii. An increase in the lattice parameter, strain, and oxygen vacancy concentration was observed as a function of ionic radii. Among the various dopants in CNPs, La3+ with higher ionic radii having smaller crystallite size (7.9 nm) and higher vacancy displayed better peroxidase, oxidase, and hydroxyl radical (HO center dot) scavenging activities. The kinetic parameters for the peroxidase and oxidase activities were found to be superior with K-m = 0.217 and 0.261 mM, respectively, for 5 mol % La3+-doped CNPs. To divulge the role of dopant concentration on the structural properties, we also explored using 10 and 20 mol % La3+ doping in CNPs. Because of the smaller crystallite size (6.7 nm) and higher defect level (3.12 X 10(21) cm(-3)), 20% La3+ doping showed superior peroxidase and oxidase activities, as shown by the low K-m values. CNPs exhibit both peroxidase and oxidase activities in a concentration-dependent manner. Moreover, CNPs exhibit concentration-dependent peroxidase and oxidase activities that can be selectively activated for various theranostic applications. Thus, our results demonstrate the crucial role of ionic radii and the concentration of RE3+ dopants on defect formation in CNPs for improved antioxidant properties of ceria.

We developed a novel approach to characterize the electrochemical reaction of solid oxide fuel cell. The method constrained electrode-electrolyte interface geometry and thereby limited reaction area for charge transfer. Reactive ion etch (RIE) and sputtering techniques were used and the well-defined geometry of interfaces was realized as patterned strips. The number of strips of the pattern shape was fully consistent with the value of charge transfer impedance. The confined interface structure also helped maintain open circuit voltage for 10 h. This new approach proposes an alternative to quantitatively analyze different electrode materials for SOFC operation while excluding consideration for structural variables.

Development of high proton conducting, chemically stable electrolyte for solid oxide fuel cell application still remains as a major challenge. In this work, yttrium (0, 5, 10, 15 and 20 mol%) doped barium zirconate synthesised by hydrothermal assisted coprecipitation exhibited highly crystalline cubic perovskite. The results demonstrate that the proton conductivity is higher than oxygen ion conductivity measured in the temperature range of 200-600 degrees C. The 20 mol% Y doped BaZrO3 exhibited higher protonic conductivity (6.1 mScm(-1)) with an activation energy 0.64 eV under the reducing atmosphere. The Mott -Schottky analysis carried out in hydrogen atmosphere at 200 degrees C revealed that the barrier height of doped BaZrO3 reduced from 0.6 to 0.2 V. The Schottky depletion layer width also decreased from 4 to 2 nm with the increase in yttrium concentration and the boiling water test showed good phase stability. Our study highlights the critical role of space charge in the grain boundary and its suppression with the increase in dopant concentration. The results demonstrate that Y doped BaZrO3 sintered at low temperature is a promising candidate as the electrolyte material for the intermediate temperature proton conducting solid oxide fuel cells. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The development of highly structured nano-cermet anodes, operating on CO2 electro-reduced via industrial waste carbon, and their reaction mechanism.