Synergistic ultraviolet and visible light photo-activation enables intensified low-temperature methanol synthesis over copper/zinc oxide/alumina

Although photoexcitation has been employed to unlock the low-temperature equilibrium regimes of thermal catalysis, mechanism underlining potential interplay between electron excitations and surface chemical processes remains elusive. Here, we report an associative zinc oxide band-gap excitation and copper plasmonic excitation that can cooperatively promote methanol-production at the copper-zinc oxide interfacial perimeter of copper/zinc oxide/alumina (CZA) catalyst. Conversely, selective excitation of individual components only leads to the promotion of carbon monoxide production. Accompanied by the variation in surface copper oxidation state and local electronic structure of zinc, electrons originating from the zinc oxide excitation and copper plasmonic excitation serve to activate surface adsorbates, catalysing key elementary processes (namely formate conversion and hydrogen molecule activation), thus providing one explanation for the observed photothermal activity. These observations give valuable insights into the key elementary processes occurring on the surface of the CZA catalyst under light-heat dual activation

Surfactant Induced Synthesis of LiAlH4 and NaAlH4 Nanoparticles for Hydrogen Storage

LiAlH4 and NaAlH4 are considered to be promising hydrogen storage materials due to their high hydrogen density. However, their practical use is hampered by the lack of hydrogen reversibility along with poor kinetics. Nanosizing is an effective strategy to enable hydrogen reversibility under practical conditions. However, this has remained elusive as the synthesis of alanate nanoparticles has not been explored. Herein, a simple solvent evaporation method is demonstrated to assemble alanate nanoparticles with the use of surfactants as a stabilizer. More importantly, the roles of the surfactants in enabling control over particle size and morphology was determined. Surfactants with long linear carbon chains and matching the hard character of alanates are more prone to lead to the formation of small particles of ~10 nm due to steric hindrance. This can result in significant shifts in the temperature for hydrogen release

Surfactant Induced Synthesis of LiAlH₄ and NaAlH₄ Nanoparticles for Hydrogen Storage

LiAlH4 and NaAlH4 are considered to be promising hydrogen storage materials due to their high hydrogen density. However, their practical use is hampered by the lack of hydrogen reversibility along with poor kinetics. Nanosizing is an effective strategy to enable hydrogen reversibility under practical conditions. However, this has remained elusive as the synthesis of alanate nanoparticles has not been explored. Herein, a simple solvent evaporation method is demonstrated to assemble alanate nanoparticles with the use of surfactants as a stabilizer. More importantly, the roles of the surfactants in enabling control over particle size and morphology was determined. Surfactants with long linear carbon chains and matching the hard character of alanates are more prone to lead to the formation of small particles of ~10 nm due to steric hindrance. This can result in significant shifts in the temperature for hydrogen release

Calcium Phosphate Growth at Electropolished Titanium Surfaces

This work investigated the ability of electropolished Ti surface to induce Hydroxyapatite (HA) nucleation and growth in vitro via a biomimetic method in Simulated Body Fluid (SBF). The HA induction ability of Ti surface upon electropolishing was compared to that of Ti substrates modified with common chemical methods including alkali, acidic and hydrogen peroxide treatments. Our results revealed the excellent ability of electropolished Ti surfaces in inducing the formation of bone-like HA at the Ti/SBF interface. The chemical composition, crystallinity and thickness of the HA coating obtained on the electropolished Ti surface was found to be comparable to that achieved on the surface of alkali treated Ti substrate, one of the most effective and popular chemical treatments. The surface characteristics of electropolished Ti contributing to HA growth were discussed thoroughly

Nanosized Magnesium Electrochemically Deposited on a Carbon Nanotubes Suspension: Synthesis and Hydrogen Storage

Herein, we report on a novel method for deposition of magnesium (Mg) nanoparticles at the surface of carbon materials. Through the suspension of carbon nanotubes (CNTs) in an electrolyte containing di-n-butylmagnesium as a precursor, Mg nanoparticles were effectively deposited at the surface of the CNTs as soon as these touched the working electrode. Through this process, CNTs supported Mg particles as small as 1 nm were synthesized and the distribution of the nanoparticles was found to be influenced by the concentration of the CNTs in the electrolyte. Hydrogenation of these nanoparticles at 100°C was found to lead to low temperature hydrogen release starting at 150°C, owing to shorter diffusion paths and higher hydrogen mobility in small Mg particles. However, these hydrogen properties drastically degraded as soon as the hydrogenation temperature exceeded 200°C and this may be related to the low melting temperature of ultrasmall Mg particles

Calcium Phosphate Growth at Electropolished Titanium Surfaces

This work investigated the ability of electropolished Ti surface to induce Hydroxyapatite (HA) nucleation and growth in vitro via a biomimetic method in Simulated Body Fluid (SBF). The HA induction ability of Ti surface upon electropolishing was compared to that of Ti substrates modified with common chemical methods including alkali, acidic and hydrogen peroxide treatments. Our results revealed the excellent ability of electropolished Ti surfaces in inducing the formation of bone-like HA at the Ti/SBF interface. The chemical composition, crystallinity and thickness of the HA coating obtained on the electropolished Ti surface was found to be comparable to that achieved on the surface of alkali treated Ti substrate, one of the most effective and popular chemical treatments. The surface characteristics of electropolished Ti contributing to HA growth were discussed thoroughly

Reversible Hydrogen Storage in Solid‐State Reaction Derived Core‐Shell NaBH4@Ni Nanocubes

The method to synthesize high‐capacity complex hydride nanostructures, such as borohydrides, decorated with metallic shells has surfaced as an attractive approach for enabling reversible hydrogen storage. However, the current solvent‐based synthesis methods of such core‐shell nanostructures are limited by solvents/hydrides compatibility issues and the low solubility of the shell precursor in such solvents. Herein, for the first time, an alternative solid‐state method to prepare core‐shell‐like nanostructures is reported. Simply, by mixing and heating vanadium (V)‐doped sodium borohydride (V‐NaBH4) cores and nickelocene (as nickel precursor) at 150 °C, it is possible to decorate V‐NaBH4 with Ni, which shows an improved hydrogen release (≈8 mass% H2) at 350 °C and a net reversible hydrogen capacity of 2 mass%. Detailed structural investigations reveal that the in‐situ formed VxBy and NixBy are responsible for superior hydrogen absorption in the core‐shell material, where these boride species around the shell/interfaces suppress the loss of Na or B and the formation of B12H12 during hydrogen release/uptake. This work opens solvent‐free pathways to design and control the chemical composition of core–shell (boro)hydrides for practical hydrogen storage

Superior MgH2 Kinetics with MgO Addition: A Tribological Effect

The kinetics of hydrogen absorption/desorption in magnesium can be improved without any catalysis assistance and MgO was found to be more effective than the best catalyst reported so far, i.e., Nb2O5. Herein, a quantitative analysis of the hydrogen kinetics in magnesium modified with MgO was performed in order to identify possible rate controlling mechanisms. While hydrogen absorption was found to be diffusion controlled as commonly reported, hydrogen desorption evolved from nucleation and growth to an interface controlled process depending on the desorption temperature. Comparison with the effect of Nb2O5 indicates that similar rate limiting steps occur regardless of the oxide additive. These findings are reconciled by considering the tribological effect of solid oxide additives, as a correlation between oxides electronegativity and improvement in hydrogen kinetics was found. Such a correlation clearly highlights the mechanical effect of solid oxides in facilitating the grinding and stabilisation of small magnesium particles for efficient and fast hydrogen kinetics

Superior Performance of an Iron-Platinum/Vulcan Carbon Fuel Cell Catalyst

This work reports on the synthesis of iron-platinum on Vulcan carbon (FePt/VC) as an effective catalyst for the electrooxidation of molecular hydrogen at the anode, and electroreduction of molecular oxygen at the cathode of a proton exchange membrane fuel cell. The catalyst was synthesized by using the simple polyol route and characterized by XRD and HRTEM along with EDS. The catalyst demonstrated superior electrocatalytic activity for the oxygen reduction reaction and the oxidation of hydrogen with a 2.4- and 1.2-fold increase compared to platinum on Vulcan carbon (Pt/VC), respectively. Successful application of FePt/VC catalyst in a self-breathing fuel cell also showed a 1.7-fold increase in maximum power density compared to Pt/VC. Further analysis by accelerated stress test demonstrated the superior stability of FePt on the VC substrate with a 4% performance degradation after 60,000 cycles. In comparison, a degradation of 6% after 10,000 cycles has been reported for Pt/Ketjenblack