2 research outputs found
Unraveling the Interfacial Electron Transfer in Various Photocathode Architectures for Advancing a Photobattery
A quintessential
element that enables devices to convert solar
energy into chemical energy is a photoelectrode. Toward developing
such a lithium-ion photobattery for converting and storing the energy
captured from light, we herein report the fundamental solid-state
electron transfer of an optimized photoelectrode. It combines two
materials that are well known to promote photomediated electron transfer
in solution: an organic dye, perylene diimide (PDI), and a redox active
material, lithium iron phosphate (LFP). The energetic compatibility
of the materials to sustain light-mediated electron transfer in the
solid state was confirmed by ultraviolet photoemission spectroscopy.
Various photoelectrode architectures were fabricated by incorporating
PDI into a conventional lithium-ion battery electrode. Illuminating
the photoelectrodes revealed that the best configuration of the light
harvesting/redox active components was a device fabricated from discrete
multiple layers rather than an arbitrary combination of the various
materials. Indeed, neither photoscreening nor self-quenching of PDI
was found with the optimized architecture. The light-triggered electron
transfer process from LFP to excited PDI was confirmed by a decrease
in the fluorescence when PDI was deposited on top of an electrode.
Encapsulating LFP with a conductive coating was required to enable
the charge transfer between the light harvesting components and the
redox active components. The role of the conductive material in the
light-triggered process was evaluated by Raman spectroscopy. It was
found that doped poly(3,4-ethylenedioxythiophene) could replace the
commonly used carbon black as the conductive layer. Raman spectroscopy
further confirmed the photomediated interfacial electron transfer
between the photoelectrode components. The architecture that deactivated
the PDI emission most efficiently was an outer coating of PDI on the
redox active particles rather than a simple top coating on the electrode.
No additional electrochemical features were observed during galvanostatic
cycling with PDI, and there was no chemical modification of the materials
according to post-cycling analyses. The oxidation of LFP by photoexcited
PDI in the photoelectrode was further confirmed by the increase in
current during periodic illumination. These findings confirm the suitability
of the materials for use in a photoelectrode and pave the way for
further device developments
Apple Pectin-Based Hydrogel Electrolyte for Energy Storage Applications
Demand
for flexible energy storage devices is rapidly increasing
due to the development of new wearable and flexible electronics. These
developments require improved integration of energy storage devices
to meet the design specifications of these products. Polymer hydrogels
are an alternative class of flexible electrolytes that can be used
in power source systems. Herein, we present a new sustainable hydrogel
electrolyte material made with apple pectin. Using an easy solution
casting approach, a bio-based hydrogel was formed via pectin gelation.
The resultant hydrogel was made with environmentally benign compounds
including water, zinc and/or lithium sulfate salt, and a bio-based
polymer. This hydrogel electrolyte exhibits ambient temperature ionic
conductivities that are similar to those found in aqueous liquid electrolytes
(ā¼5 Ć 10ā2 S cmā1),
depending on electrolyte hydration. Its wide thermal stability window
enables the electrolyte to be used at both low temperatures (ā20
Ā°C) and intermediate temperatures (50 Ā°C), without significant
changes in ionic conductivity (>10ā3 S cmā1). By proposing an energy-oriented solution using
one of the food
industryās major waste materials, we report a novel approach
to processing a bio-based polymer for energy storage purposes