Device generates hydrogen from sunlight

Rice University engineers have developed a device that combines halide perovskite semiconductors with electrocatalysts, to turn sunlight into hydrogen with high efficiency. The new technology is a step forward for clean energy and could serve as a platform for a range of chemical reactions that use solar-harvested electricity to convert feedstocks into fuels. The lab of chemical and biomolecular engineer Aditya Mohite built the integrated photoreactor using an anticorrosion barrier that insulates the semiconductor from water without impeding the transfer of electrons. According to a study published in Nature Communications, the device achieved a 20.8% solar-to-hydrogen conversion efficiency.

Austin Fehr, one of the study’s lead authors, said using sunlight as an energy source to manufacture chemicals is one of the largest hurdles to a clean energy economy. “Our goal is to build economically feasible platforms that can generate solar-derived fuels. Here, we designed a system that absorbs light and completes electrochemical water-splitting chemistry on its surface,” Fehr said.

The device is called a photoelectrochemical cell because the absorption of light, its conversion into electricity and the use of the electricity to power a chemical reaction all occur in the same device. Until now, using photoelectrochemical technology to produce green hydrogen was hampered by low efficiencies and the high cost of semiconductors. “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 new device was created by turning a solar cell into a reactor that could use harvested energy to split water into oxygen and hydrogen. The challenge the researchers had to overcome was that halide perovskites are unstable in water and coatings used to insulate the semiconductors ended up either disrupting their function or damaging them. The researchers tried different materials and techniques, before coming across a solution.

The researchers discovered that they 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. “Our results are the highest efficiency for photoelectrochemical cells without solar concentration, and the best overall for those using halide perovskite semiconductors,” Fehr said.

The researchers showed their barrier design worked for different reactions and with different semiconductors, making it applicable across many systems. Fehr said further advancements to stability and scale could help open up the hydrogen economy and change the way humans make things from fossil fuel to solar fuel.

“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,” Mohite said.

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