Innovation On The Hydrogen Generation Front

With the relatively cheap price of oil from production to pump, alternative energies, especially R&D seem to have taken a back seat. Battery technologies are progressing (slowly), wind and solar seem stagnant, as do most other innovative technologies, including fusion (well, enough said there). An alternative energy source that has always intrigued me, though, is hydrogen – the base element.

Obviously, it has challenges for safe storage and use, but producing it economically and profitably have also been challenges.

In college I was very interested in converting water to its base elements – hydrogen and oxygen – using a process called electrolysis. It works as the decomposition of water (H₂O) into oxygen (O₂) and hydrogen gas (H₂) as an electric current is passed through the water. This technique can be used to make hydrogen fuel (hydrogen gas) and breathable oxygen; however, today most raw hydrogen fuel is made from natural gas. Not exactly a sustainable alternative source or method.

Even with this drawback, hydrogen is considered an important source of “clean” energy, and the cleanest way to produce hydrogen gas is to split water into hydrogen and oxygen. But, scientists have struggled to develop cost-effective water-splitting techniques.

Recently, though, researchers at North Carolina State University have created a technique using a new catalyst for converting methane and water into hydrogen and a fuel feedstock, called syngas, with the assistance of solar power. The team of chemical engineering researchers used a catalytic material that is more than three times more efficient at converting water to hydrogen gas than previous thermal-water-splitting methods.

“We’re excited about the new material and process because it converts water, inexpensive natural gas and clean, renewable solar energy into valuable syngas and hydrogen fuels,” said Feng He, a PhD student in the lab of Professor Fanxing Li at NC State.

How Can Water Be Turned Into Fuel?

Syngas is a mixture of carbon monoxide and hydrogen, and it’s used as a feedstock for commercial processes that produce synthetic diesel fuels, olefins, and methanol.

The technique hinges on a new catalytic material that is a composite of iron oxide and lanthanum strontium iron oxide, also known as LSF. Researchers have known that iron oxide can be used as a catalyst for thermal water splitting, but it is not very efficient. The addition of LSF significantly improves iron oxide’s activity, making it far more efficient. Using the new composite, the researchers were able to convert 77% of the water they used, in the form of steam, into hydrogen. The previous best conversion mark for thermal water-splitting was around 20%. Pretty impressive results!

“We’re optimistic that commercial utilization of this technique could promote the efficient usage of solar energy and domestic natural gas, produce relatively low carbon dioxide emissions while making liquid transportation fuel, and generate low-cost, high-purity hydrogen,” he said.

 Schematic of the hybrid process for generating liquid fuel and hydrogen from LSF

The researchers’ new technique used methane injected into a reactor that is heated with solar energy. The chamber contains the catalytic composite, which reacts with the methane to produce syngas and carbon dioxide. This process “reduces” the composite particles, stripping them of oxygen. The syngas is removed from the system and the reduced composite particles are diverted into a second reactor. High-temperature steam is then pumped into the second reactor, where it reacts with the reduced composite particles to produce hydrogen gas that is at least 97% pure. This process also reoxygenates the composite particles, which can then be re-used with the methane, starting the cycle all over again.

The steam initially has to be produced with an external energy source, but once the cycle is initiated, the chemical reactions produce enough heat to convert water into steam without an external heat source. “We’ve created the catalytic particles and conducted every step of this process, but only in separate batches,” He said. “We’re now in the process of building a circulating bed reactor to operate this entire cycle in a continuous mode in real world conditions. Next steps include fine-tuning the catalytic compound to make it better and cheaper, improving the overall process, and developing better reactors.”

Li-ion Battery Technology Produces Hydrogen

Developers of electric cars that used lithium-ion batteries are racing hydrogen-fueled vehicles to see which will succeed the greenhouse gas-producing gasoline-powered internal combustion engine.

They’ve been racing in different directions—until now. Scientists at Stanford University have created a low-voltage, low-cost “water splitter” that uses a single catalyst to continuously produce both hydrogen and oxygen from water. That catalyst was created by a team co-led by Yi Cui, an associate professor of materials science and engineering at Stanford and of photon science at the SLAC National Accelerator Laboratory, using lithium-ion battery technology.

How Hydrogen Fuel Is Made

“Our group has pioneered the idea of using lithium-ion batteries to search for catalysts,” Cui said. “Our hope is that this technique will lead to the discovery of new catalysts for other reactions beyond water splitting.”

The water-splitting device is described in a study published on June 23 in the journal Nature Communications and was announced in a Stanford news release the same day.

Despite its sustainable reputation, and as mentioned earlier, most commercial-grade hydrogen is made from natural gas. As a greener alternative, researchers have sought to develop a cheap and efficient way to extract pure hydrogen from water. A conventional water-splitting device consists of two electrodes submerged in a water-based electrolyte.

“Our water splitter is unique because we only use one catalyst, nickel-iron oxide, for both electrodes,” said graduate student Haotian Wang, lead author of the study. “This bi-functional catalyst can split water continuously for more than a week with a steady input of just 1.5 volts of electricity. That’s an unprecedented water-splitting efficiency of 82% at room temperature.”

Wang and his colleagues discovered that nickel-iron oxide, which is cheap and easy to produce, is actually more stable than some commercial catalysts made of precious metals. The team built a conventional water splitter with one platinum and one iridium, Wang said. That device started off well, needing only 1.56 volts to split water initially, but within 30 hours the voltage needed to be increased nearly 40%, “a significant loss of efficiency,” according to Wang.

In conventional water splitters, the hydrogen and oxygen catalysts often require different electrolytes with different pH–one acidic, one alkaline–to remain stable and active. “For practical water splitting, an expensive barrier is needed to separate the two electrolytes, adding to the cost of the device,” Wang said.

To find catalytic material suitable for both electrodes, the Stanford team borrowed a technique used in battery research called lithium-induced electrochemical tuning. The idea is to use lithium ions to chemically break the metal oxide catalyst into smaller and smaller pieces. “This process creates tiny particles that are strongly connected, so the catalyst has very good electrical conductivity and stability,” Cui said.

Technical and business challenges aside, and they are admittedly big challenges, I remain a strong proponent of hydrogen production and implementation. Forget the Hindenburg; dream for a sustainable future. These two projects are just the beginning of what I believe to be a proliferation of possibilities going forward — hydrogen and beyond.

Tags: electrolysis, hydrogen, syngas

This entry was posted on Thursday, September 17th, 2015 at 19:16. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.