Rice University researchers have created an efficient, low-cost device that splits water to produce hydrogen fuel. The platform developed by the Brown School of Engineering lab of Rice materials scientist Jun Lou integrates catalytic electrodes and perovskite solar cells that, when triggered by sunlight, produce electricity. The current flows to the catalysts that turn water into hydrogen and oxygen, with a sunlight-to-hydrogen efficiency as high as 6.7%.

A schematic and electron microscope cross-section show the structure of an integrated, solar-powered catalyst to split water into hydrogen fuel and oxygen. The module developed at Rice University can be immersed into water directly to produce fuel when exposed to sunlight. Illustration by Jia Liang

The integrated device consists of two series-connected perovskite solar cells (PSCs) and two CoP catalyst electrodes, which can be immersed into an aqueous solution directly for solar-driven water splitting.

The platform introduced by Lou, lead author and Rice postdoctoral fellow Jia Liang and their colleagues in the ACS journal ACS Nano is a self-sustaining producer of fuel that, they say, should be simple to produce in bulk.

The concept is broadly similar to an artificial leaf. What we have is an integrated module that turns sunlight into electricity that drives an electrochemical reaction. It utilizes water and sunlight to get chemical fuels.

Jun Lou

Perovskites are crystals with cubelike lattices that are known to harvest light. The most efficient perovskite solar cells produced so far achieve an efficiency above 25%, but the materials are expensive and tend to be stressed by light, humidity and heat.

Jia has replaced the more expensive components, like platinum, in perovskite solar cells with alternatives like carbon. That lowers the entry barrier for commercial adoption. Integrated devices like this are promising because they create a system that is sustainable. This does not require any external power to keep the module running.

Liang said the key component may not be the perovskite but the polymer that encapsulates it, protecting the module and allowing to be immersed for long periods.

Others have developed catalytic systems that connect the solar cell outside the water to immersed electrodes with a wire. We simplify the system by encapsulating the perovskite layer with a Surlyn (polymer) film.

Jia Liang

The patterned film allows sunlight to reach the solar cell while protecting it and serves as an insulator between the cells and the electrodes, Liang said.

The researchers said they will continue to improve the encapsulation technique as well as the solar cells themselves to raise the efficiency of the modules.

The research was funded by the Peter M. and Ruth L. Nicholas Postdoctoral Fellowship in Nanotechnology from Rices Smalley-Curl Institute, the Welch Foundation, the National Science Foundation-backed Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment, and Fundamental Research Funds for the Central Universities, China.

Resources

Jia Liang, Xiao Han, Yunxiu Qiu, Qiyi Fang, Boyu Zhang, Weipeng Wang, Jing Zhang, Pulickel M. Ajayan, and Jun Lou (2020) A Low-Cost and High-Efficiency Integrated Device toward Solar-Driven Water SplittingACS Nano doi: 10.1021/acsnano.9b09053

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Rice U team creates low-cost, high-efficiency integrated device for solar-driven water splitting; solar leaf - Green Car Congress