In the present work, change in electronic properties due to structural modification of bilayer g-C3N4 using density functional theory has been studied. We have considered shifting and rotation of one layer parallel to the second fixed layer and optimised three different arrangements. The stability of the bilayer was examined by calculating the total energy of all the structures. Specific bilayer arrangement having 180° rotation has been found most stable. The study of density of states reveals band gap of this structure to be 0.60 eV. From HOMO-LUMO and partial density of states it is seen that the stability and properties of bilayer g-C3N4 highly depends on the arrangement of N-2p and C-2p orbitals in both the layers. The inclusion of van der Waals (vdW) interaction changes the properties in z axis due to coupled orbital and columbic interaction between the layers and individual orbitals.
Amorphous materials
are used in multitude of catalytic
applications,
including electrocatalytic water-splitting. Identification and investigation
of active sites in amorphous catalysts are rarely reported, mainly
owing to the complexity of the systems. Herein, we report an amorphous
bifunctional Co–W–B electrocatalyst for hydrogen evolution
reaction (HER) and oxygen evolution reaction (OER). The optimized
Co–W–B catalyst showed promising overpotential values
of 97 mV (HER) and 292 mV (OER), respectively, to achieve 10 mA cm–2 in 1 M KOH, with good stability. The promoting effect
of W in Co–B was investigated experimentally, while computational
tools were used to identify all the possible catalytic sites in an
amorphous Co–W–B model and classify the most preferred
sites for HER and OER. The presence of multi-catalytic sites with
specific selectivity toward HER and OER was observed, which explained
the bifunctional activity of Co–W–B. This study will
foster better understanding of the origin of catalytic activity in
similar amorphous systems.
A novel,
eco-friendly, polymorphic graphitic carbon nitride (g-C3N4) bilayer with its potential application in photoresponsive
and physicochemical properties enhanced due to interlayer coupling
lacks investigation of different stacking configurations, interlayer
atomic superposition, and their effect on photoactive reaction sites.
Using the hybrid density functional theory, structural, electronic,
optical, and photocatalytic properties of nine spatially modified
bilayers referred to as S0–S8, together
with site-dependent oxygen/hydrogen evolution reactions (OER/HER)
on the most photoactive bilayer (S3), have been explored
in this work. vdW bilayers arranged considering all possibilities
of interlayer atom–atom/atom–bond alignment along with
the upper layer rotated by 0° (AA) and 180° (AB) on energy
and force minimization are classified into planar (corrugated) geometry
with band gap decrement (increment) compared to the monolayer, indicating
the role of π-delocalization. Increased mobility, feasible surface
migration, and reduced rate of recombination for photogenerated charge
carriers in S3 along with the highest optical absorbance
indicated its importance over monolayer and other bilayer configurations.
Among the different active reaction sites, the best suitable site
on S3 reveals 2 and 3 (20) times drop in value of overpotential
for OER and HER (with an additional H2O molecule), respectively,
against the monolayer. Current analysis displays efficient charge
carrier separation, in which charge transfer within the bilayer on
intermediate adsorption and formation of an interfacial electric field
illustrates the stepwise reaction mechanism and proclaims the synergistic
effect of π-conjugation and interlayer orbital interaction for
surface activation and improved photocatalytic activity of the g-C3N4 bilayer as compared to the monolayer.
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