Fabrication of 3D NiO-YSZ structures for enhanced performance of solid oxide fuel cells and electrolysers

Increasing densities of (electrode–electrolyte-pore) triple phase boundaries (TPBs) / reaction sites enhance performances of solid oxide electrochemical reactors (SOERs) in both fuel cell (SOFC) and electrolyser (SOE) modes. Inkjet 3D printing is capable of construction of ceramic microstructures on support layers, enabling fabrication of SOERs with enhanced active area to geometric area ratios, thereby up-scaling effective areas / TBP lengths per unit volume. A Ni(O)-YSZ functional layer was designed and 3D inkjet printed with a surface of circular pillars, a facile geometry for printing that increased the interfacial to geometric area ratio. Deposition of further functional layers and sintering resulted in fully fabricated reactors with structures: H2O-H2 | Ni(O)-YSZ support | Ni(O)-YSZ pillars | YSZ | YSZ-LSM | O2, Air. The corresponding planar structured cell also was fabricated with the same components, for comparison of its electrochemical performance with that of the pillar-structured cell. The latter exhibited performance enhancement over its planar counterpart by factors of ca. 1.5 in fuel cell mode, ca. 3 in steam electrolysis mode, and ca. 4–5 in CO2 electrolysis mode, thereby demonstrating the potential of geometric structuring of electrode | electrolyte interfaces by 3D printing for developing higher performance SOERs

Inkjet 3D-printing of functional layers of solid oxide electrochemical reactors: a review

The review paper overviews principles of inkjet printing and ink formulation, subsequently a literature summary on inkjet-printed solid oxide electrochemical reactors printed with 2D and 3D structures, followed by challenges limiting the technique

3-D inkjet printed solid oxide electrochemical reactors III. cylindrical pillared electrode microstructures

Inkjet printing is a scalable technique that can fabricate customised three-dimensional microstructures, reproducibly, accurately, and with high material utilisation, by printing multiple layers sequentially onto previously printed layers, to produce architectures tailored in this case to electrochemical reactors. Printable yttria-stabilised zirconia (YSZ) and lanthanum strontium manganite (LSM) inks were formulated to enable fabrication of solid oxide electrochemical reactors (SOERs): H2O-H2 | Ni(O)-YSZ | YSZ | YSZ pillars | LSM | O2. Of the geometries studied, equi-sized, hexagonally-arranged cylindrical pillars were predicted to produce the largest ratio of interfacial to geometric (cross-sectional) areas. However, this neglects effects of potential and current density distributions that constrain up-scaling to more modest factors. Hence, using kinetic parameter values from the literature, finite element computational simulations of the pillared SOER in (H2 - O2) fuel cell mode predicted peak power densities of 0.11 W cm−2 at 800 °C, whereas its counterpart with only a planar electrolyte layer produced only 0.05 W cm−2; i.e. the pillars were predicted to enhance peak power densities by ca. 2.3. Arrays of several thousand YSZ cylindrical pillars were printed, with post-sintering diameter, height, and spacing of 25, 95 and 63 μm, respectively. LSM was inkjet-printed onto the pillars, and sintered subsequently, to produce contiguous films ca. 4 μm thick. In (H2 - O2) fuel cell mode at 725, 770, and 795 °C, these reactors produced peak power densities of 0.09, 0.21, 0.30 W cm−2, respectively, 3–6 times greater than the performance of ‘benchmark’ Ni(O)-YSZ | YSZ | LSM reactors inkjet-printed with planar cathodes operating under the same conditions, thereby demonstrating the benefit of inkjet printing as a fabrication technique for SOERs

Predicting optimal geometries of 3D-printed solid oxide electrochemical reactors

Solid oxide electrochemical reactors (SOERs) may be operated in fuel cell (SOFC) or electrolyser (SOE) modes, at temperatures > 800 K, depending on electrolyte and electrode materials. In electrolyser mode, current densities of ≥ ca. 104 A m−2 are achievable at potential differences ideally at the thermoneutral values of 1.285 V for steam splitting or 1.46 V for CO2 splitting at 750 °C. As for large scale chemical processes in general, such reactors are required to be energy efficient, economic, of scalable design and fabrication, and durable ideally over ≥ ca. 10 years. Increasing densities of electrode | electrolyte interfacial areas (and electrode | electrolyte | pore triple phase boundaries) of solid oxide fuel cells or electrolysers offers one means of increasing performance, reproducibility, durability and potentially decreasing cost. Three-dimensional structuring of those interfaces can be achieved by 3D printing, but modelling is required to optimise geometries. Using kinetic parameter values from the literature, COMSOL Multiphysics® finite element software was used to predict effects of 3D geometries, increasing interfacial to geometric area ratios, on SOER performances for YSZ ((ZrO2)0.92(Y2O3)0.08) oxide ion conducting electrolyte and Ni-YSZ electrode based cells, relative to corresponding planar structures with < 10 μm thick planar YSZ electrolyte. For the negative electrode, electrolyte and electrode layers were inkjet printed on Ni(O)-YSZ substrate precursors, then sintered. For the positive electrode, porous lanthanum strontium manganite (LSM: La0.8Sr0.2MnO3-δ) was brush-coated over the (gas-tight) YSZ, then sintered to produce complete SOERs: H2O-H2 | Ni(O)-YSZ | YSZ-YSZ pillars | YSZ-LSM | LSM | O2. Results are reported showing that, in the case of solid YSZ pillars, despite interfacial electrode | electrolyte areas being up scaled by factors of 10–150 depending on height (10–150 μm), current densities were predicted to increase by only ca. 1.14 in electrolysis mode and peak power densities were predicted to increase by ca. 1.93 in fuel cell mode. This was due to increased ionic current path length along the pillars, increasing ohmic potential losses relative to faradaic impedances; as expected, such predictions depend strongly on electrode kinetic parameter values. After sintering the porous Ni(O)-YSZ pillars and their subsequent reduction with H2 to nickel, they were assumed to constitute equipotential surfaces, depending on current collector design. Predicted current densities were up to 1011 mA cm−2, far greater than in solid YSZ pillars, ultimately limited by reactant or product mass transport through porous pillars of increasing height

Consecutive junction-induced efficient charge separation mechanisms for high-performance MoS2/quantum dot phototransistors

Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel concept involving the modulation of the built-in potential within the QD layers for creating a new hybrid MoS2/PbS QDs phototransistor with consecutive type II junctions. The effects of the built-in potential across the depletion region near the type II junction interface in the QD layers are found to improve the photoresponse as well as decrease the response times to 950 μs, which is the faster response time (by orders of magnitude) than that recorded for previously reported 2D/QD phototransistors. Also, by implementing an electric-field modulation of the MoS2 channel, our experimental results reveal that the detectivity can be as large as 1 × 1011 jones. This work demonstrates an important pathway toward designing hybrid phototransistors and mixed-dimensional van der Waals heterostructures

Core components for effective infection prevention and control programmes: new WHO evidence-based recommendations

Abstract Health care-associated infections (HAI) are a major public health problem with a significant impact on morbidity, mortality and quality of life. They represent also an important economic burden to health systems worldwide. However, a large proportion of HAI are preventable through effective infection prevention and control (IPC) measures. Improvements in IPC at the national and facility level are critical for the successful containment of antimicrobial resistance and the prevention of HAI, including outbreaks of highly transmissible diseases through high quality care within the context of universal health coverage. Given the limited availability of IPC evidence-based guidance and standards, the World Health Organization (WHO) decided to prioritize the development of global recommendations on the core components of effective IPC programmes both at the national and acute health care facility level, based on systematic literature reviews and expert consensus. The aim of the guideline development process was to identify the evidence and evaluate its quality, consider patient values and preferences, resource implications, and the feasibility and acceptability of the recommendations. As a result, 11 recommendations and three good practice statements are presented here, including a summary of the supporting evidence, and form the substance of a new WHO IPC guideline

Wall-thickness-dependent strength of nanotubular ZnO

We fabricate nanotubular ZnO with wall thickness of 45, 92, 123 nm using nanoporous gold (np-Au) with ligament diameter at necks of 1.43 mu m as sacrificial template. Through micro-tensile and micro-compressive testing of nanotubular ZnO structures, we find that the exponent m in (sigma) over bar proportional to (rho) over bar (m), where (sigma) over bar is the relative strength and (rho) over bar is the relative density, for tension is 1.09 and for compression is 0.63. Both exponents are lower than the value of 1.5 in the Gibson-Ashby model that describes the relation between relative strength and relative density where the strength of constituent material is independent of external size, which indicates that strength of constituent ZnO increases as wall thickness decreases. We find, based on hole-nanoindentation and glazing incidence X-ray diffraction, that this wall-thickness-dependent strength of nanotubular ZnO is not caused by strengthening of constituent ZnO by size reduction at the nanoscale. Finite element analysis suggests that the wall-thickness-dependent strength of nanotubular ZnO originates from nanotubular structures formed on ligaments of np-Au

Analyses of associations between three positionally cloned asthma candidate genes and asthma or asthma-related phenotypes in a Chinese population

<p>Abstract</p> <p>Background</p> <p>Six asthma candidate genes, ADAM33, NPSR1, PHF11, DPP10, HLA-G, and CYFIP2, located at different chromosome regions have been positionally cloned following the reported linkage studies. For ADAM33, NPSR1, and CYFIP2, the associations with asthma or asthma-related phenotypes have been studied in East Asian populations such as Chinese and Japanese. However, for PHF11, DPP10, and HLA-G, none of the association studies have been conducted in Asian populations. Therefore, the aim of the present study is to test the associations between these three positionally cloned genes and asthma or asthma-related phenotypes in a Chinese population.</p> <p>Methods</p> <p>Two, five, and two single nucleotide polymorphisms (SNPs) in the identified top regions of PHF11, DPP10, and HLA-G, respectively, were genotyped in 1183 independent samples. The study samples were selected based on asthma affectation status and extreme values in at least one of the following three asthma-related phenotypes: total serum immunoglobulin E levels, bronchial responsiveness test, and skin prick test. Both single SNP and haplotype analyses were performed.</p> <p>Results</p> <p>We found that DPP10 was significantly associated with bronchial hyperresponsiveness (BHR) and BHR asthma after the adjustment for multiple testing; while the associations of PHF11 with positive skin reactions to antigens and the associations of HLA-G with BHR asthma were only nominally significant.</p> <p>Conclusion</p> <p>Our study is the first one to provide additional evidence that supports the roles of DPP10 in influencing asthma or BHR in a Chinese population.</p