China's molecular-level photothermal energy technology has made breakthroughs

Recently, the scientific research team led by Professor Feng Wei of Tianjin University designed the world's first photosensitive molecular/nanotemplate composite structure, and prepared a new single/double-branched azobenzene molecular covalently grafted graphene hybrid material, which broke through the problem of molecular-level photothermal energy storage and controllable release, and provided an important material foundation and design direction
for the high-energy, long-term storage and conversion of solar energy in the future.
The relevant research results were published online in
the Journal of Materials Chemistry, a top journal in the field of materials chemistry.

Traditional solar energy utilization is mainly concentrated in the field of photovoltaics and solar heat, the energy cycle mode is generally converted into electrical energy, and then converted into heat energy, there are generally large energy losses, high acquisition costs, storage and conversion difficulties and other problems
.
Photothermal direct conversion and storage technology is a new technology that subverts the traditional energy utilization mode and provides clean and stable energy, among which molecular-level chemical heat storage materials are a hot spot and difficult point for scientists
.

The azo benzene/graphene hybrid material prepared by Feng Wei's team is a brand-new molemular-level chemical heat storage material
that can directly carry out "light energy storage - heat energy release".
Based on the ortho and para-substituent design of photosensitive molecules, the research team covalently grafted the photosensitive molecule azo benzene on the surface of graphene (nanocarbon material), and by increasing the grafting density of azo benzene and changing the spatial molecular configuration, the azo benzene formed multiple intermolecular hydrogen bonds on the graphene surface, and realized the regulation
of molecular energy storage density and stability with hydrogen bonds 。 The experimental results show that the heat storage density of azobenzene/graphene hybrid materials reaches 138Wh/kg, which is 2~3 times the heat storage density of existing materials, which is the highest value reported internationally, and can be comparable to the existing commercial soft pack lithium-ion batteries (90-100Wh/kg).

The material has outstanding optical heat storage cycle characteristics and light controllable release characteristics, and can achieve 50 optical heat storage cycles, which is equivalent to 4.
5 years
of continuous use.

At present, the research team is further optimizing and building molecular-level optical heat storage devices
.
"In the future, it can provide thermal energy output for systems that require heat energy and temperature control, such as aerospace, automobiles, and adaptive insulation suits, and improve energy supply efficiency
.
" Feng Wei said
.