New method to produce green hydrogen offers promising path to carbon neutrality

ANN ARBOR—A new method to achieve clean hydrogen through solar water splitting offers a promising path to achieving net-zero carbon emissions. Newly funded by the Department of Energy (DoE), a University of Michigan research team aims to stabilize perovskite-based solar cells to produce highly-efficient, low-cost, ultrastable green hydrogen fuel.

“Perovskite has great potential to harvest solar energy and drive water splitting, giving us clean hydrogen fuels,” said Zetian Mi, Professor of Electrical and Computer Engineering at the University of Michigan, who leads the project. “It’s truly a carbon neutral approach.”

It’s truly a carbon neutral approach.

Prof. Zetian Mi

Solar water splitting is a process that replicates photosynthesis by using the sun to separate hydrogen from water. That hydrogen can then be used as a clean energy alternative to fossil fuels. However, the current method to produce hydrogen through artificial photosynthesis, which is known as “gray hydrogen,” still results in fossil fuel emissions.

“Hydrogen itself is clean, but the current process of producing hydrogen is not,” Mi said. “For example, if we drive a hydrogen fuel cell vehicle, as a driver, we aren’t really producing CO₂. But in other places in the U.S., we’re emitting lots of CO₂ to produce the hydrogen we use to power that car.”

Blue hydrogen is a method of hydrogen production in which the fossil fuel emissions are trapped and stored to prevent environmental impact. While this is more sustainable than gray hydrogen, blue hydrogen is not practical long-term. To achieve truly clean hydrogen, or “green hydrogen,” the entire production process has to be free of fossil fuel emissions. But for this to be possible, solar cell technology needs an upgrade.

“Current solar cell technology is mostly based on silicon, but many people believe the next generation will be perovskite,” Mi said. “This material has similar and even higher efficiency than silicon, yet it doesn’t require as much of the material, and the overall cost is much lower.”

Perovskite has many possibilities for improving the sustainability of artificial photosynthesis and a variety of optoelectronic devices. However, it’s also notoriously unstable.

“Ideally you want a solar cell panel to last for 20 or 30 years or more,” Mi said. “But the stability of perovskite materials is often limited to hours or days, depending on how they’re packaged.”

To solve this problem, Mi’s team will use gallium nitride (GaN), a material widely used in LED lighting and the electronics industry, to stabilize the surface of perovskite materials. This method is based on their recent work done in collaboration with Lawrence Berkeley National Laboratory and Lawrence Livermore National Laboratory through the DoE’s HydroGEN consortium, where they proved that with GaN surface protection, high efficiency Si-based photoelectrodes can operate for more than 3,000 hours without performance degradation.

“Using gallium nitride to stabilize the surface of perovskite is very promising and could open many new possibilities for this amazing material,” Mi said. “This could enable the stable operation of perovskite-based solar cells and other optoelectronic devices.”

This could enable the stable operation of perovskite-based solar cells and other optoelectronic devices.

Prof. Zetian Mi

The development and synthesization of the perovskite material is led by Prof. Yanfa Yan from University of Toledo, who serves as a co-PI on the project. Mi’s team — which includes co-PI Pallab Bhattacharya, the Charles M. Vest Distinguished University Professor and James R. Mellor Professor of Engineering — integrates the perovskite with their nitrides and with silicon to achieve simultaneously high efficiency and long-term stability. Mi’s team also tests the water-splitting capabilities in their lab.

The project is funded through the DoE’s Energy Earthshots Initiative, which seeks to reduce the cost of clean hydrogen by 80% to one dollar per one kilogram in one decade (known as the “1 1 1” initiative).

Some of the intellectual property related to this work has been licensed to NS Nanotech, Inc. and NX Fuels, Inc., which were co-founded by Mi . T and launched with support from Innovation Partnerships, the central hub for research commercialization activity at the University of Michigan. The University of Michigan and Mi have a financial interest in both companies.

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