10 research outputs found
Understanding the NaCl-dependent behavior of hydrogen production of a marine bacterium, Vibrio tritonius
Biohydrogen is one of the most suitable clean energy sources for sustaining a fossil fuel independent society. The use of both land and ocean bioresources as feedstocks show great potential in maximizing biohydrogen production, but sodium ion is one of the main obstacles in efficient bacterial biohydrogen production. Vibrio tritonius strain AM2 can perform efficient hydrogen production with a molar yield of 1.7 mol H-2/mol mannitol, which corresponds to 85% theoretical molar yield of H-2 production, under saline conditions. With a view to maximizing the hydrogen production using marine biomass, it is important to accumulate knowledge on the effects of salts on the hydrogen production kinetics. Here, we show the kinetics in batch hydrogen production of V. tritonius strain AM2 to investigate the response to various NaCl concentrations. The modified Han-Levenspiel model reveals that salt inhibition in hydrogen production using V. tritonius starts precisely at the point where 10.2 g/L of NaCl is added, and is critically inhibited at 46 g/L. NaCl concentration greatly affects the substrate consumption which in turn affects both growth and hydrogen production. The NaCl-dependent behavior of fermentative hydrogen production of V. tritonius compared to that of Escherichia coli JCM 1649 reveals the marine-adapted fermentative hydrogen production system in V. tritonius. V. tritonius AM2 is capable of producing hydrogen from seaweed carbohydrate under a wide range of NaCl concentrations (5 to 46 g/L). The optimal salt concentration producing the highest levels of hydrogen, optimal substrate consumption and highest molar hydrogen yield is at 10 g/L NaCl (1.0% (w/v))
Cross-talk elimination for lenslet array near eye display based on eye-gaze tracking
Lenslet array (LA) near-eye displays (NEDs) are a recent technical development that creates a virtual image in the field of view of one or both eyes. A problem occurs when the user’s pupil moves out of the LA-NED eye box (i.e., cross-talk) making the image look doubled or ghosted. It negatively impacts the user experience. Although eye-gaze tracking can mitigate this problem, the effect of the solution has not been studied to understand the impact of pupil size and human perception. In this paper, we redefine the cross-talk region as the practical pupil movable region (PPMR50), which differs from eye box size because it considers pupil size and human visual perception. To evaluate the effect of eye-gaze tracking on subjective image quality, three user studies were conducted. From the results, PPMR50 was found to be consistent with human perception, and cross-talk elimination via eye-gaze tracking was better understood in a static gaze scenario. Although the system latency prevented the complete elimination of cross-talk for fast movements or large pupil changes, the problem was greatly alleviated. We also analyzed system delays based on PPMR50, which we newly defined in this paper and provided an optimization scheme to meet the maximum eyeball rotation speed
Breaking the Structure–Activity Relationship in Toluene Hydrogenation Catalysis by Designing Heteroatom Ensembles Based on a Single-Atom Alloying Approach
Hydrogenation of toluene (TOL) to methylcyclohexane (MCH)
is one
of the hydrogen carrier systems desired for social integration. Supported
Pt nanoparticle catalysts are effective for this application. However,
Pt is rare, expensive, and in short supply, limiting its practical
applications. Therefore, the key issue for TOL hydrogenation is how
to substantially reduce the amount of Pt required for the catalyst.
Because a specific ensemble of Pt atoms, that is dominantly formed
on the surface of the Pt nanoparticle, is required for achieving higher
catalytic performance, there is a limit to the number of precious
Pt that can be conserved by simply reducing the particle size. The
structure sensitivity established in the existing heterogeneous catalyst
so far makes it difficult to design precious metal-conserving catalysts
with both high activity and atomic efficiency. Here, a strategy for
breaking the above limitations is reported. Our approach uses the
heteroatom ensemble (HAE) on Pt single-atom alloyed 3d transition-metal
nanoparticle catalysts (Pt1M SAAs, M = Co, Ni, Cu). The role of the
TOL fixation/activation site is assigned to the atomic M sites on
HAE, whereas the H2-activation site is to the Pt single-atom
site on HAE. The atomic-scale division of roles within the HAE improves
the efficiency of competitive adsorption of TOL/H2, which
is important for boosting TOL hydrogenation. To maximize the synergistic
effect at the adjacent sites, the atomic composition, geometric configuration,
and electronic state of these active sites as well as the density
of the HAE were tuned by the chemical composition and particle size
of Pt1M SAAs. High activity was observed on the Pt1Co SAA with a particle
size of 1.8 nm and Pt/Co molar ratio of 0.002. The Pt mass-specific
activity reached 219 mol/gPt/h, which was 23 times higher
than that in a conventional Pt nanoparticle-supported catalyst. Using
a set of well-defined Pt1M SAAs, high-angle annular dark-field scanning
transmission electron microscopy, Pt LIII-edge X-ray absorption
fine structure spectroscopy, coupled with periodic density functional
theory and ab initio molecular dynamics simulation, we proved the
origin of the structure sensitivity at an atom-to-nanometer scale.
The present work sheds light on the significance of regulations of
the coordination environment of the Pt single-atom site, atomic composition,
and particle size of Pt1M SAA for creating high activity, durability,
and Pt-utilization efficiency for catalytic applications relevant
to hydrogen carrier systems
Breaking the Structure–Activity Relationship in Toluene Hydrogenation Catalysis by Designing Heteroatom Ensembles Based on a Single-Atom Alloying Approach
Hydrogenation of toluene (TOL) to methylcyclohexane (MCH)
is one
of the hydrogen carrier systems desired for social integration. Supported
Pt nanoparticle catalysts are effective for this application. However,
Pt is rare, expensive, and in short supply, limiting its practical
applications. Therefore, the key issue for TOL hydrogenation is how
to substantially reduce the amount of Pt required for the catalyst.
Because a specific ensemble of Pt atoms, that is dominantly formed
on the surface of the Pt nanoparticle, is required for achieving higher
catalytic performance, there is a limit to the number of precious
Pt that can be conserved by simply reducing the particle size. The
structure sensitivity established in the existing heterogeneous catalyst
so far makes it difficult to design precious metal-conserving catalysts
with both high activity and atomic efficiency. Here, a strategy for
breaking the above limitations is reported. Our approach uses the
heteroatom ensemble (HAE) on Pt single-atom alloyed 3d transition-metal
nanoparticle catalysts (Pt1M SAAs, M = Co, Ni, Cu). The role of the
TOL fixation/activation site is assigned to the atomic M sites on
HAE, whereas the H2-activation site is to the Pt single-atom
site on HAE. The atomic-scale division of roles within the HAE improves
the efficiency of competitive adsorption of TOL/H2, which
is important for boosting TOL hydrogenation. To maximize the synergistic
effect at the adjacent sites, the atomic composition, geometric configuration,
and electronic state of these active sites as well as the density
of the HAE were tuned by the chemical composition and particle size
of Pt1M SAAs. High activity was observed on the Pt1Co SAA with a particle
size of 1.8 nm and Pt/Co molar ratio of 0.002. The Pt mass-specific
activity reached 219 mol/gPt/h, which was 23 times higher
than that in a conventional Pt nanoparticle-supported catalyst. Using
a set of well-defined Pt1M SAAs, high-angle annular dark-field scanning
transmission electron microscopy, Pt LIII-edge X-ray absorption
fine structure spectroscopy, coupled with periodic density functional
theory and ab initio molecular dynamics simulation, we proved the
origin of the structure sensitivity at an atom-to-nanometer scale.
The present work sheds light on the significance of regulations of
the coordination environment of the Pt single-atom site, atomic composition,
and particle size of Pt1M SAA for creating high activity, durability,
and Pt-utilization efficiency for catalytic applications relevant
to hydrogen carrier systems
Breaking the Structure–Activity Relationship in Toluene Hydrogenation Catalysis by Designing Heteroatom Ensembles Based on a Single-Atom Alloying Approach
Hydrogenation of toluene (TOL) to methylcyclohexane (MCH)
is one
of the hydrogen carrier systems desired for social integration. Supported
Pt nanoparticle catalysts are effective for this application. However,
Pt is rare, expensive, and in short supply, limiting its practical
applications. Therefore, the key issue for TOL hydrogenation is how
to substantially reduce the amount of Pt required for the catalyst.
Because a specific ensemble of Pt atoms, that is dominantly formed
on the surface of the Pt nanoparticle, is required for achieving higher
catalytic performance, there is a limit to the number of precious
Pt that can be conserved by simply reducing the particle size. The
structure sensitivity established in the existing heterogeneous catalyst
so far makes it difficult to design precious metal-conserving catalysts
with both high activity and atomic efficiency. Here, a strategy for
breaking the above limitations is reported. Our approach uses the
heteroatom ensemble (HAE) on Pt single-atom alloyed 3d transition-metal
nanoparticle catalysts (Pt1M SAAs, M = Co, Ni, Cu). The role of the
TOL fixation/activation site is assigned to the atomic M sites on
HAE, whereas the H2-activation site is to the Pt single-atom
site on HAE. The atomic-scale division of roles within the HAE improves
the efficiency of competitive adsorption of TOL/H2, which
is important for boosting TOL hydrogenation. To maximize the synergistic
effect at the adjacent sites, the atomic composition, geometric configuration,
and electronic state of these active sites as well as the density
of the HAE were tuned by the chemical composition and particle size
of Pt1M SAAs. High activity was observed on the Pt1Co SAA with a particle
size of 1.8 nm and Pt/Co molar ratio of 0.002. The Pt mass-specific
activity reached 219 mol/gPt/h, which was 23 times higher
than that in a conventional Pt nanoparticle-supported catalyst. Using
a set of well-defined Pt1M SAAs, high-angle annular dark-field scanning
transmission electron microscopy, Pt LIII-edge X-ray absorption
fine structure spectroscopy, coupled with periodic density functional
theory and ab initio molecular dynamics simulation, we proved the
origin of the structure sensitivity at an atom-to-nanometer scale.
The present work sheds light on the significance of regulations of
the coordination environment of the Pt single-atom site, atomic composition,
and particle size of Pt1M SAA for creating high activity, durability,
and Pt-utilization efficiency for catalytic applications relevant
to hydrogen carrier systems