Efficient hydrogen production via solar-powered processes typically involves the use of photovoltaic or photoelectrochemical (PEC) cells to harness solar energy and split water (H2O) into hydrogen (H2) and oxygen (O2) via a process known as water electrolysis. High efficiency in this process is critical for cost-effective and environmentally friendly hydrogen production.
Rice University researchers have developed a device that combines next-generation halide perovskite semiconductors with electrocatalysts in a single, durable, cost-effective, and scalable device that converts sunlight into hydrogen with unprecedented efficiency.
The new technology is a significant step forward for clean energy and could serve as a platform for a wide range of chemical reactions that convert feedstocks into fuels using solar-harvested electricity.
Aditya Mohite’s lab built the integrated photoreactor with an anticorrosion barrier that protects the semiconductor from water without interfering with electron transfer. The device achieved a 20.8% solar-to-hydrogen conversion efficiency, according to a study published in Nature Communications.
Our goal is to create economically viable platforms for producing solar-derived fuels. We created a system that absorbs light while also completing electrochemical water-splitting chemistry on its surface.
Austin Fehr
“Using sunlight as an energy source to manufacture chemicals is one of the most significant barriers to a clean energy economy,” said Austin Fehr, a doctoral student in chemical and biomolecular engineering and one of the study’s lead authors. “Our goal is to create economically viable platforms for producing solar-derived fuels. We created a system that absorbs light while also completing electrochemical water-splitting chemistry on its surface.”
The device is called a photoelectrochemical cell because light is absorbed, converted into electricity, and used to power a chemical reaction all happen in the same device. Until now, using photoelectrochemical technology to generate green hydrogen has been hampered by low efficiencies and high semiconductor costs.
“All devices of this type produce green hydrogen using only sunlight and water, but ours is exceptional because it has record-breaking efficiency and it uses a semiconductor that is very cheap,” Fehr said.
The Mohite lab and its collaborators created the device by turning their highly-competitive solar cell into a reactor that could use harvested energy to split water into oxygen and hydrogen. The challenge they had to overcome was that halide perovskites are extremely unstable in water and coatings used to insulate the semiconductors ended up either disrupting their function or damaging them.
“Over the last two years, we’ve gone back and forth trying different materials and techniques,” said Michael Wong, a Rice chemical engineer and co-author on the study. After lengthy trials failed to yield the desired result, the researchers finally came across a winning solution.
“Our key insight was that you needed two layers to the barrier, one to block the water and one to make good electrical contact between the perovskite layers and the protective layer,” Fehr said. “Our results are the highest efficiency for photoelectrochemical cells without solar concentration, and the best overall for those using halide perovskite semiconductors.
“It is a first in a field that has historically been dominated by prohibitively expensive semiconductors, and it may represent a pathway to commercial feasibility for this type of device for the first time ever,” Fehr said. The researchers demonstrated that their barrier design worked for various reactions and with various semiconductors, making it applicable to a wide range of systems.
“We hope that such systems will serve as a platform for driving a wide range of electrons to fuel-forming reactions using abundant feedstocks with only sunlight as the energy input,” said Mohite. “With further improvements to stability and scale, this technology could open up the hydrogen economy and change the way humans make things, shifting from fossil fuel to solar fuel,” Fehr added.
