Modification of carbon nitride based
polymeric 2D materials for
tailoring their optical, electronic and chemical properties for various
applications has gained significant interest. The present report demonstrates
the synthesis of a novel modified carbon nitride framework with a
remarkable 3:5 C:N stoichiometry (C3N5) and
an electronic bandgap of 1.76 eV, by thermal deammoniation of the
melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units
are bridged together with azo linkage, which constitutes an entirely
new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen.
Extended conjugation due to overlap of azo nitrogens and increased
electron density on heptazine nucleus due to the aromatic π
network of heptazine units lead to an upward shift of the valence
band maximum resulting in bandgap reduction down to 1.76 eV. XRD,
He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman,
FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties
of C3N5 are distinct from pristine carbon nitride
(g-C3N4). When used as an electron transport
layer (ETL) in MAPbBr3 based halide perovskite solar cells,
C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as
1.3 V, while C3N5 blended with MA
x
FA1–x
Pb(I0.85Br0.15)3 perovskite active layer
achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer
for TiO2 photoanodes in photoelectrochemical water splitting.
Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from
aqueous solution reaching complete equilibrium within 10 min, which
is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled
with plasmonic silver nanocubes promotes plasmon-exciton coinduced
surface catalytic reactions reaching completion at much low laser
intensity (1.0 mW) than g-C3N4, which showed
sluggish performance even at high laser power (10.0 mW). The relatively
narrow bandgap and 2D structure of C3N5 make
it an interesting air-stable and temperature-resistant semiconductor
for optoelectronic applications while its electron-rich character
and intrasheet cavity make it an attractive supramolecular adsorbent
for environmental applications.
The direct conversion of mechanical energy into electricity by nanomaterial-based devices offers potential for green energy harvesting . A conventional triboelectric nanogenerator converts frictional energy into electricity by producing alternating current (a.c.) triboelectricity. However, this approach is limited by low current density and the need for rectification . Here, we show that continuous direct-current (d.c.) with a maximum density of 10 A m can be directly generated by a sliding Schottky nanocontact without the application of an external voltage. We demonstrate this by sliding a conductive-atomic force microscope tip on a thin film of molybdenum disulfide (MoS). Finite element simulation reveals that the anomalously high current density can be attributed to the non-equilibrium carrier transport phenomenon enhanced by the strong local electrical field (10-10 V m) at the conductive nanoscale tip . We hypothesize that the charge transport may be induced by electronic excitation under friction, and the nanoscale current-voltage spectra analysis indicates that the rectifying Schottky barrier at the tip-sample interface plays a critical role in efficient d.c. energy harvesting. This concept is scalable when combined with microfabricated or contact surface modified electrodes, which makes it promising for efficient d.c. triboelectricity generation.
Boosting the photovoltaic power output is the key to large-scale implementation of solar cell technologies for renewable energy applications. Traditional solar energy harvesting is limited by the costly fabrication of p-n junctions, the duration of sunlight irradiation, and theoretical output limit. In this work, Liu et al. demonstrate that the photovoltaic power output can be dramatically enhanced by mechanical friction between a metal and a semiconductor, leading to the development of a new power generation approach called tribo-photovoltaic generator. It enables highly efficient solar-mechanical energy co-harvesting in the daytime as well as mechanical energy at night. The tribo-photovoltaic effect may be utilized for co-harvesting of solar and mechanical energy in various scenarios such as ocean tidal energy harvesters, wind turbines, and aerospace energy collectors.
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.