Chemical Engineering March 2023 - 5

Chementator
This coating boosts the efficiency of
perovskite solar cells
P
erovskite materials have great
potential as a lightweight and
low-cost option for solar panels,
but in the past have not
been seen as stable or durable enough
for widespread use in large-scale solarpower
installations. Now, a new coating
developed by a research team at
Purdue University (West Lafayette, Ind.;
www.purdue.edu), led by chemical engineering
professor Letian Dou, could
overcome these challenges. " Perovskite
can degrade quickly when exposed to
moisture, heat or light, which limits its
commercial
application. Our organic
ligand coating can reduce perovskite
defects and passivate the surface, making
the material much more stable. At
the same time, the organic ligand can
act as a semiconductor to help conduct
charge, which helps to improve electrical
performance, " explains Dou.
While much work has been done to
develop coatings to protect and passivate
perovskite, many of these options
focused on insulating materials
that actually decreased charge transport,
adds Dou. The ligand is a bipolar,
conjugated molecule - one end
is charged to bind with the perovskite,
while is the other is hydrophobic to protect
against moisture. To form the coating,
the ligand is dissolved in a solvent
at a dilute concentration (typically less
than 1 mg/mL). According to Dou, the
cost to manufacture the ligand is very
low, and based on well-established
methods. Furthermore, the perovskite
surface only requires a very thin coating
- just 4-5 nm - meaning that the
coating would not add significant cost
to solar panels.
Over a 2,000-h testing period at high
heat, the coated panel maintained over
80% of its original power conversion
efficiency. " This is much higher performance
than the control device without
the ligand coating, " says Dou. Next, the
team is considering ligands with new
functional moieties and multiple binding
sites to further enhance stability, and
investigating ways to enhance solubility
and processability to improve coverage.
They also have a contract with a
major solar-power company to begin
testing the technology.
Edited by:
Gerald Ondrey
ODC TECHNOLOGY
Last month, Covestro AG (Leverkusen,
Germany; www.covestro.com)
started up a new world-scale facility
for the production of chlorine in Tarragona,
Spain. It is the first world-scale
production plant for chlorine based
upon the oxygen-depolarized cathode
(ODC) technology invented by
Covestro and its partners. The new
plant ensures an efficient, sustainable
and independent supply of chlorine
and caustic soda to methylene
diphenyl diisocyanate (MDI) production
in Tarragona. MDI is a precursor
for the manufacture of rigid polyurethane
foam used to insulate refrigeration
appliances and buildings. The
€200-million investment has created
50 new jobs on site.
The ODC technology was developed
by Covestro in collaboration with thyssenkrupp
nucera (Dortmund, Germany;
www.thyssenkrupp-nucera.
com), with the first demonstration
plant started up in 2011 in KrefeldUerdingen,
Germany (Chem. Eng.,
May 2010, p. 11). Compared to the
currently predominant conventional
(Continues on p. 8)
Perform dewatering, drying and cleaning of liquid waste
in a single process
recently commissioned, 150,000-ton/yr facility
in Sumner, Wash. is the first wastewatertreatment
plant to deploy a new liquid-waste
treatment technology. Owned by Generate
Upcycle (San Francisco, Calif.; www.generatecapital.
com), and operated in partnership with Sedron Technologies,
LLC (Sedro-Woolley, Wash.; www.sedron.
com), the facility treats septage- and biosolids-laden
slurry using Sedron's Varcor technology to split the
waste into clean water, a dry solid and a solution of lowboiling-point
constituents, such as ammonia, explains
Stanley Janicki, chief revenue officer at Sedron Technologies.
" A Varcor system is unique, in that it replaces
Sedron Technologies
A
four traditional systems in a wastewater-treatment plant
- dewatering, drying and sidestream nutrient removal
for nitrogen and phosphorus - while ensuring that the
energy source is electricity, making the process easily
decarbonized, " adds Janicki.
The process combines mechanical vapor recompression
and distillation with thin-film and scraped-surface
drying on a series of hollow rotating disks (diagram).
Slurry is poured over the outside of the disks, and solids
collect on the disk while the vaporized portion is sent
for compression. The higher-temperature compressed
vapor is passed back through the inside of the disks
and condensed, providing the heat needed to continue
to vaporize the slurry product. Because of this configuration,
the system requires little heat input and
no treatment chemicals. Notably, the water produced
from the Varcor system is clean enough to be
blended with the plant's effluent water, which significantly
reduces the overall load on the plant.
Furthermore, the process yields both solid and
aqueous nitrogen fertilizers, which can be upcycled
as key agricultural inputs, explains Bill Caesar, president
of Generate Upcycle. " The ability to extract nitrogen
allows the Sumner facility to reduce nutrient pollution
by diverting hundreds of thousands of pounds
of nitrogen from existing wastewater plants and producing
a fertilizer that displaces the production of fossil
fuel-derived fertilizers, " he adds.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2023
5
http://www.covestro.com http://www.purdue.edu http://www.thyssenkrupp-nucera.com http://www.thyssenkrupp-nucera.com http://www.generatecapital.com http://www.generatecapital.com http://www.sedron.com http://www.sedron.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering March 2023

Table of Contents for the Digital Edition of Chemical Engineering March 2023
