Experimental and theoretical modeling of Fe , Co , Cu , Mn based electrocatalysts for oxygen reduction

Abstract Experience gained during efforts towards optimization of noble metal free electrocatalysts for oxygen reduction is simultaneously used to understand the chemical and morphological necessities for inducing efficient multielectron transfer catalysis. The analysis of many preparative experimental steps between the moderately performing metal porphyrines and the highly efficient transition metal and sulfur containing pyrolised catalyst material contributes to the following model of the catalyst 1. The metals function enclosed in nitrogen or graphitic environment where they are shielded against oxidation. 2. The metals can be exchanged but are not identical in their efficiency. 3. Higher efficiency is only achieved, when the function of a binary reaction center is warranted. 4. The carbonization of the environment is critical and provides intercalated metal centers and attached metal complexes in graphite environment for interaction with the nitrogen chelated partner center in the simultaneously obtained graphene layers. Experimental support for these models from EXAFS, RAMAN, Mössbauer and X ray spectroscopy is given and a parallel is drawn with the cytochrome oxidase oxygen reduction catalysis, which is proposed to proceed according to roughly the same mechanism. A special effort is made to discuss strategies for shielding and protecting catalytically active abundant transition metals against chemical reaction with oxygen or hydrogen peroxide

Dynamic Operation of a Heat Exchanger in a Thermally Integrated Photovoltaic Electrolyzer

The outdoor operation of an up scaled thermally photovoltaic electrolyzer PV EC , constructed using a heat exchanger HE made of low cost materials, compared to its nonintegrated counterpart to quantify heat transfer and its effects, is studied. Thermal coupling of the PV and EC can reduce the difference between their temperatures, benefitting device performance. Such devices can produce hydrogen at rooftop installations of small to medium sized nonindustrial buildings. The devices are tested outdoors using automated real time monitoring. Under amp; 8776;880 amp; 8201;W amp; 8201;m amp; 8722;2 peak irradiance, they produced hydrogen at amp; 8776;120 and amp; 8776;110 amp; 8201;mL amp; 8201;min amp; 8722;1 rate with and without HE, respectively, corresponding to about 8.5 and 7.8 solar to hydrogen efficiencies. During about 700 amp; 8201;h of testing, the HE is beneficial at over amp; 8776;500 amp; 8201;W amp; 8201;m amp; 8722;2 due to cyclic device operation. Under lower irradiance levels, pumping previously heated electrolyte through the HE increases the PV and reduces the electrolyte temperature, reducing the device performance. The HE increases the cumulative hydrogen production amp; 8776;800 amp; 8201;L from both devices , so even relatively modest heat transfer rates can improve the PV EC operation. Improving the HE should further increase the benefits, but additional measures may be needed to maximize the hydrogen productio

Host, Suppressor, and Promoter The Roles of Ni and Fe on Oxygen Evolution Reaction Activity and Stability of NiFe Alloy Thin Films in Alkaline Media

Understanding the oxygen evolution reaction OER activity and stability of the NiFe based materials is important for achieving low cost and highly efficient electrocatalysts for practical water splitting. Here, we report the roles of Ni and Fe on the OER activity and stability of metallic NiFe and pure Ni thin films in alkaline media. Our results support that Ni OH 2 NiOOH does not contribute to the OER directly, but it serves as an ideal host for Fe incorporation, which is essential for obtaining high OER activity. Furthermore, the availability of Fe in the electrolyte is found to be important and necessary for both NiFe and pure Ni thin films to maintain an enhanced OER performance, while the presence of Ni is detrimental to the OER kinetics. The impacts of Fe and Ni species present in KOH on the OER activity are consistent with the dissolution re deposition mechanism we proposed. Stability studies show that the OER activity will degrade under prolonged continuous operation. Satisfactory stability can, however, be achieved with intermittent OER operation, in which the electrocatalyst is cycled between degraded and recovered states. Accordingly, two important ranges, that is, the recovery range and the degradation range, are proposed. Compared to the intermittent OER operation, prolonged continuous OER operation i.e., in the degradation range generates a higher NiOOH content in the electrocatalyst, which is likely related to the OER deactivation. If the electrode works in the recovery range for a certain period, that is, at a sufficiently low reduction potential, where Ni3 is reduced to Ni2 , the OER activity can be maintained and even improved if Fe is also present in the electrolyt

Corneal ulcerative disease in dogs under primary veterinary care in England: epidemiology and clinical management

Abstract Background Corneal ulcerative disease (CUD) has the potential to adversely affect animal welfare by interfering with vision and causing pain. The study aimed to investigate for the first time the prevalence, breed-based risk factors and clinical management of CUD in the general population of dogs under primary veterinary care in England. Results Of 104,233 dogs attending 110 clinics participating within the VetCompass Programme from January 1st to December 31st 2013, there were 834 confirmed CUD cases (prevalence: 0.80%, 95% confidence interval (CI) 0.75–0.86). Breeds with the highest prevalence included Pug (5.42% of the breed affected), Boxer (4.98%), Shih Tzu (3.45%), Cavalier King Charles Spaniel (2.49%) and Bulldog (2.41%). Purebred dogs had 2.23 times the odds (95% CI 1.84–2.87, P < 0.001) of CUD compared with crossbreds. Brachycephalic types had 11.18 (95% CI 8.72–14.32, P < 0.001) and spaniel types had 3.13 (95% CI 2.38–4.12, P < 0.001) times the odds for CUD compared with crossbreds. Pain was recorded in 385 (46.2%) cases and analgesia was used in 455 (54.6%) of dogs. Overall, 62 (7.4%) cases were referred for advanced management and CUD contributed to the euthanasia decision for 10 dogs. Conclusions Breeds such as the Pug and Boxer, and conformational types such as brachycephalic and spaniels, demonstrated predisposition to CUD in the general canine population. These results suggest that breeding focus on periocular conformation in predisposed breeds should be considered in order to reduce corneal disease

Three Dimensional Characterization of Nano Particles Catalyst

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Probing structural effects of pyrolysed CoTMPP based electrocatalysts for oxygen reduction via new preparation strategies

The preparation of cobalt tetramethoxyphenylphorphyrin CoTMPP based oxygen reduction catalysts by heat treatment was investigated by rotating disc electrode measurements, thermal analysis and X ray diffractometry in order to improve the electrochemical activity. It was found that the activity of pyrolysed carbon supported CoTMPP is limited by a non porous morphology of the reaction products. A new preparation strategy is introduced, which leads to finer dispersed and smaller catalytic particles by the addition of metal oxalates as foaming agents. The mass related current densities of these Co containing catalysts are very close to the activity of commercial platinum catalysts. The presence of sulfur in the process provokes an further pronounced increase of the performance. Remarkably, the catalytic activity increases with the square of the electrochemical active surface area. This structure dimensional effect is tentatively explained by an increase of micro porosity of the sponge like catalyst particles and an improvement of surface specific properties, which are not jet clearly identifie