11 research outputs found
Cognitive Alignment through Artefacts in Distributed Innovation: The Role of Initial Code Release in Open Source Software
We present results from density functional
theory calculations
of the lithium adsorption onto 2D graphitic carbon nitride membranes,
C<sub>3</sub>N<sub>4</sub> and C<sub>6</sub>N<sub>8</sub> and bulk
C<sub>3</sub>N<sub>4</sub>. We find that lithium adsorbs preferentially
over the triangular pores with a high adsorption energy. We also find
that lithium adsorption severely distorts the membrane and bulk material.
The lithium mainly interacts with the pyridinic nitrogen in the material,
which enables a large lithium uptake. However, the pyridinic nitrogen
is also responsible for the instability of the material. We also present
experimental results on the charge and discharge capacities of C<sub>6</sub>N<sub>8</sub>. These mirror the theoretical prediction that
the material shows a high lithium uptake which is, however, irreversible
Pyrene-Functionalized PTMA by NRC for Greater π–π Stacking with rGO and Enhanced Electrochemical Properties
Nitroxide radical polymers can undergo
both excellent electrochemical redox reactions and a rapid “click”
coupling reaction with carbon-centered radicals (i.e., nitroxide radical
coupling (NRC) reaction). In this work, we report a strategy to functionalize
polyÂ(2,2,6,6,-tetramethylpiperidinyl-1-oxyl methacrylate) (PTMA) with
pyrene side groups through a rapid and near quantitative NRC reaction.
This resulted in PÂ(TMA-<i>co</i>-PyMA) random copolymers
with near quantitative amounts of pyrene along the PTMA chain for
greater π–π interaction with rGO, while the nitroxide
radicals on the polymer could simultaneously be used for energy storage.
These copolymers can bind with reduced graphene oxide (rGO) and form
layered composites through noncovalent π–π stacking,
attaining molecular-level dispersion. Electrochemical performance
of the composites with different polymer contents (24, 35, and 45
wt %), tested in lithium ion batteries, indicated that the layered
structures consisting of PÂ(TMA-<i>co</i>-PyMA) maintained
greater capacities at high C-rates. This simple and efficient strategy
to synthesize pyrene-functionalized polymers will provide new opportunities
to fabricate many other polymer composite electrodes for desired electrochemical
performance
Transition from the Tetragonal to Cubic Phase of Organohalide Perovskite: The Role of Chlorine in Crystal Formation of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> on TiO<sub>2</sub> Substrates
The role of chlorine in the superior
electronic property and photovoltaic
performance of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>(3–<i>x</i>)</sub>Cl<sub><i>x</i></sub> perovskite has attracted
recent research attention. Here, we study the impact of chlorine in
the perspective of the crystal structure of the perovskite layer,
which can provide important understanding of its excellent charge
mobility and extended lifetimes. In particular, we find that in the
presence of chlorine (PbCl<sub>2</sub> or CH<sub>3</sub>NH<sub>3</sub>Cl), when CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> films are deposited
on a TiO<sub>2</sub> mesoporous layer instead of a planar TiO<sub>2</sub> substrate, a stable cubic phase rather than the commonly
observed tetragonal phase is formed in CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite at room temperature. The relative peak
intensity of two major facets of cubic CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> crystals, (100)<sub>C</sub> and (200)<sub>C</sub> facets, can also be easily tuned, depending on the film thickness.
Furthermore, compared with pristine CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite films, in the presence of chlorine, CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> crystals grown on planar substrates
exhibit strong preferred orientations on (110)<sub>T</sub> and (220)<sub>T</sub> facets
Facile Synthesis of Highly Efficient One-Dimensional Plasmonic Photocatalysts through Ag@Cu<sub>2</sub>O Core–Shell Heteronanowires
A novel
class of one-dimensional (1D) plasmonic Ag@Cu<sub>2</sub>O core–shell
heteronanowires have been synthesized at room temperature for photocatalysis
application. The morphology, size, crystal structure and composition
of the products were investigated by XRD, SEM, TEM, XPS, and UV–vis
instruments. It was found the reaction time and the amount of Ag nanowires
play crucial roles in the formation of well-defined 1D Ag@Cu<sub>2</sub>O core–shell heteronanowires. The resultant 1D Ag@Cu<sub>2</sub>O NWs exhibit much higher photocatalytic activity toward degradation
of organic contaminants than Ag@Cu<sub>2</sub>O core–shell
nanoparticles or pure Cu<sub>2</sub>O nanospheres under solar light
irradiation. The drastic enhancement in photocatalytic activity could
be attributed to the surface plasmon resonance and the electron sink
effect of the Ag NW cores, and the unique 1D core–shell nanostructure
Hollow Anatase TiO<sub>2</sub> Single Crystals and Mesocrystals with Dominant {101} Facets for Improved Photocatalysis Activity and Tuned Reaction Preference
Faceting photocatalysts has attracted increasing interest
to improve photocatalytic activity by optimizing surface charge carrier
separation/transfer. In principle, a high photocatalytic activity
is co-contributed by both high surface separation/transfer and low
bulk recombination of charge carriers. However, little effort focuses
on lowering bulk recombination of charge carriers in faceted photocatalysts.
In this work, we report the synthesis of hollow anatase TiO<sub>2</sub> single crystals and mesocrystals with dominant {101} facets by a
new route with PO<sub>4</sub><sup>3–</sup>/F<sup>–</sup> as morphology controlling agent. It is found that with respect to
solid crystals, being hollow crystals and mesocrystals can substantially
improve photocatalytic activity (O<sub>2</sub>/H<sub>2</sub> evolution
from water splitting, CH<sub>4</sub> generation from photoreduction
of CO<sub>2</sub>) as a result of the synergistic effects of shortened
bulk diffusion length of carriers for the decreased bulk recombination
and increased surface area. Furthermore, the photocatalysis reaction
preference toward O<sub>2</sub> and H<sub>2</sub> evolution from water
splitting can be tuned
Porous Titania Nanosheet/Nanoparticle Hybrids as Photoanodes for Dye-Sensitized Solar Cells
Porous titania nanohybrids (NHs)
were successfully prepared by
hybridizing the exfoliated titania nanosheets with anatase TiO<sub>2</sub> nanoparticles. Various characterizations revealed that the
titania NHs as photoanodes play a trifunctional role (light harvesting,
dye adsorption, and electron transfer) in improving the efficiency
(η) of the dye-sensitized solar cells. The optimized photoanode
consisting layered NHs demonstrated a high overall conversion efficiency
of 10.1%, remarkably enhanced by 29.5% compared to that (7.8%) obtained
from the benchmark P25 nanoparticles under the same testing conditions
Liquid-Metal-Induced Hydrogen Insertion in Photoelectrodes for Enhanced Photoelectrochemical Water Oxidation
Fast
charge separation and transfer (CST) is essential for achieving
efficient solar conversion processes. This CST process requires not
only a strong driving force but also a sufficient charge carrier concentration,
which is not easily achievable with traditional methods. Herein, we
report a rapid hydrogenation method enabled by gallium-based liquid
metals (GBLMs) to modify the prototypical WO3 photoelectrode
to enhance the CST for a PEC process. Protons in solution are controllably
embedded into the WO3 photoanode accompanied by electron
injection due to the strong reduction capability of GBLMs. This process
dramatically increases the carrier concentration of the WO3 photoanode, leading to improved charge separation and transfer.
The hydrogenated WO3 photoanode exhibits over a 229% improvement
in photocurrent density with long-term stability. The effectiveness
of GBLMs treatment in accelerating the CST process is further proved
using other more general semiconductor photoelectrodes, including
Nb2O5 and TiO2
Oriented Built-in Electric Field Introduced by Surface Gradient Diffusion Doping for Enhanced Photocatalytic H<sub>2</sub> Evolution in CdS Nanorods
Element doping has
been extensively attempted to develop visible-light-driven
photocatalysts, which introduces impurity levels and enhances light
absorption. However, the dopants can also become recombination centers
for photogenerated electrons and holes. To address the recombination
challenge, we report a gradient phosphorus-doped CdS (CdS-P) homojunction
nanostructure, creating an oriented built-in electric-field for efficient
extraction of carriers from inside to surface of the photocatalyst.
The apparent quantum efficiency (AQY) based on the cocatalyst-free
photocatalyst is up to 8.2% at 420 nm while the H<sub>2</sub> evolution
rate boosts to 194.3 μmol·h<sup>–1</sup>·mg<sup>–1</sup>, which is 58.3 times higher than that of pristine
CdS. This concept of oriented built-in electric field introduced by
surface gradient diffusion doping should provide a new approach to
design other types of semiconductor photocatalysts for efficient solar-to-chemical
conversion
Liquid-Metal-Induced Hydrogen Insertion in Photoelectrodes for Enhanced Photoelectrochemical Water Oxidation
Fast
charge separation and transfer (CST) is essential for achieving
efficient solar conversion processes. This CST process requires not
only a strong driving force but also a sufficient charge carrier concentration,
which is not easily achievable with traditional methods. Herein, we
report a rapid hydrogenation method enabled by gallium-based liquid
metals (GBLMs) to modify the prototypical WO3 photoelectrode
to enhance the CST for a PEC process. Protons in solution are controllably
embedded into the WO3 photoanode accompanied by electron
injection due to the strong reduction capability of GBLMs. This process
dramatically increases the carrier concentration of the WO3 photoanode, leading to improved charge separation and transfer.
The hydrogenated WO3 photoanode exhibits over a 229% improvement
in photocurrent density with long-term stability. The effectiveness
of GBLMs treatment in accelerating the CST process is further proved
using other more general semiconductor photoelectrodes, including
Nb2O5 and TiO2
Oriented Built-in Electric Field Introduced by Surface Gradient Diffusion Doping for Enhanced Photocatalytic H<sub>2</sub> Evolution in CdS Nanorods
Element doping has
been extensively attempted to develop visible-light-driven
photocatalysts, which introduces impurity levels and enhances light
absorption. However, the dopants can also become recombination centers
for photogenerated electrons and holes. To address the recombination
challenge, we report a gradient phosphorus-doped CdS (CdS-P) homojunction
nanostructure, creating an oriented built-in electric-field for efficient
extraction of carriers from inside to surface of the photocatalyst.
The apparent quantum efficiency (AQY) based on the cocatalyst-free
photocatalyst is up to 8.2% at 420 nm while the H<sub>2</sub> evolution
rate boosts to 194.3 μmol·h<sup>–1</sup>·mg<sup>–1</sup>, which is 58.3 times higher than that of pristine
CdS. This concept of oriented built-in electric field introduced by
surface gradient diffusion doping should provide a new approach to
design other types of semiconductor photocatalysts for efficient solar-to-chemical
conversion