The first-principles approach is a useful tool for developing 2D/2D heterojunction catalysts for electro- and photo-catalytic nitrogen reduction reactions.
Doping or ion substitution is often used as an effective strategy to improve photocatalytic activities of several semiconductors. Most frequently, the dopants provide extra states to increase light absorption, alter the electronic structure, or lower the carrier recombination. This work focuses on ion substitution in Bi 2 WO 6 , where the dopants modify band-edge potentials of the catalysts. Specifically, we investigate how the electronegativity (EN) of the dopant could be used to tune the band-edge potentials and how such changes influence the photocatalytic mechanism. Compared to Te that has a lower EN, I lowers the band-edge potentials. While substitutions with both ions enhance Rh B photodegradation and benzylamine photooxidation, the modified band potentials of I-doped Bi 2 WO 6 influence the benzylamine photooxidation pathway, resulting in higher selectivity. Additionally, substitution of I 7+ in the Bi 2 WO 6 lattice improves the morphologies, decreases the band-gap energy, and reduces the carrier recombination. As a result, I-doped Bi 2 WO 6 shows almost 3 times higher %conversion while maintaining 100% selectivity in the oxidative coupling of benzylamine. The findings here signify the importance of the choices of dopants on the photocatalytic reactions and would benefit the design of other related materials for such applications.
Vanadate-based
compounds, in particular LiV3O8, are promising
candidates for cathode materials of Li-ion batteries.
Thanks to their open-layered structures and the various possible oxidation
states of the V metal center, LiV3O8 can effectively
accommodate Li ions and store electron potential. To further improve
the transport kinetics of the cathode, in this work, we used the first-principles
method to explore the effects of oxygen vacancies on Li insertion,
Li diffusion, and electronic conduction in the form of polaron hopping.
We find that the polaron is mobile in the [010] direction with an
effective hopping barrier, E
a,eff, of
0.11 eV and is sluggish in other directions with an E
a,eff of 0.56 eV. Such anisotropic conduction is also
observed in experiments. Interestingly, unlike other transition metal
oxides, formation of a polaron negligibly affects Li insertion and
diffusion, where the charge transport kinetics is solely limited by
the ion movement with an E
a,eff of 0.50
eV. The introduction of an oxygen vacancy, V
O, creates two polarons at the two nearby V centers where at
least one of them is relatively mobile (E
a,eff = 0.16 eV) contributing to electronic conductivity of the materials.
At low V
O concentrations of up to 1%,
the most stable V
O exists far from the
Li diffusion path and does not affect the ion transport kinetics.
In contrast, if the V
O concentration increases
to 2–3%, the second most stable V
O starts to form at the diffusion path, which greatly diminishes Li
diffusion. Hence, it is suggested that controlling the low concentration
of V
O within 1% can enhance electronic
conductivity by increasing the concentration of charge carriers while
maintaining the ion diffusivity of the LiV3O8 cathode.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.