September 22, 2018 | ° F

Rutgers researchers discover catalyst for renewable energy storage

While many students recognize hydrogen’s existence in water and the atmosphere, University researchers found a way to use it for renewable energy storage.

Rutgers researchers discovered a more cost-efficient substitute for storing renewable energy with hydrogen in a new study published the Royal Society of Chemistry’s journal, “Energy & Environmental Science.”

The research team partners with Proton OnSite, the largest manufacturer of electrolyzers in North America, said Charles Dismukes, a professor in the Department of Chemistry and Chemical Biology.

Funding of the research comes from the Air Force Office of Scientific Research, NATCO Pharma Ltd., as well as the University, Dismukes said.

Testing of the compound Ni5P4 has shown promising results of efficiency in driving hydrogen evolution reaction (HER) — the process of producing hydrogen by splitting water, which takes place in electrolyzers –– said Anders Laursen, a postdoctoral fellow in the Department of Chemistry and Chemical Biology.

The reverse process of combining hydrogen with oxygen to generate electricity happens in fuel cells, Laursen said.

Platinum is currently the material of choice for electrolysis — a process of using electric currents to drive a reaction, Laursen said.

The commercial product of Proton OnSite uses platinum as a hydrogen-evolving catalyst, Dismukes said.

“Hydrogen occurs on platinum surfaces with a minimum overpotential, additional energy beyond what thermal dynamic says,” Laursen said. “It is not only the best material but also reversible … Most renewable materials require quite a bit of overpotential to drive the reaction.”

Based on the testing results, the research team found the efficiency of Ni5P4 emulates that of platinum, Laursen and Dismukes said. The sizeable advantage of using Ni5P4 over platinum is a significant cost reduction.

The new catalyst can operate under alkaline conditions with stainless steel as the body of electrodes, instead of using platinum as catalyst under acidic conditions with titanium electrodes, Dismukes said.

“A difference in the costs of titanium and stainless steel has an impact on the overall cost of the construction of the electrolyzer,” Dismukes said. “Another gain is avoid using platinum which is less abundant and $1,100 more per ounce, versus a material that's on the pennies and dollars.”

One of the ways to assess efficiencies of catalyst is the Tafel slope, Laursen said. Tafel slope is the amount of potential that needs to be applied in order to generate 10 times more hydrogen.

“For platinum, that number is 29, for our material (it’s) 33,” he said. “That’s within the experimental uncertainty.”

There is a distinction between renewable hydrogen and non-renewable hydrogen, even though it is a clean energy that can be used in cars or as fuel, Laursen said.

The team focuses on obtaining renewable hydrogen by splitting water, as opposed to the steam reforming method, he said.

“(Steam reforming) is the reaction of natural gas and steam, where you create hydrogen and CO2,” Laursen said. “So it is not a renewable resource, but it is a hydrogen resource.”

The team’s ultimate goal is to have the renewable hydrogen produced used as an agent for energy storage, Laursen said.

“We can use (the hydrogen) and get electricity back when needed,” he said. “The advantage of storing energy in compressed hydrogen container versus battery is that hydrogen is light and easily reversible.”

The idea of examining nickel phosphide comes from the composition and structure of hydrogenizers, a type of biological enzyme that acts as a catalyst in biology, Dismukes said.

Hydrogenizers are made of proteins and have active sites comprised of metal lines, Dismukes said. Those sites include nickel, iron, sulfur and more.

“It’s really looking at enzymes, understanding how they work and translating the key principles of chemistry from the enzymes into this synthetic construct,” he said.

Kelly Patraju, a School of Arts and Sciences senior, has been working with Laursen for two years since the start of the research. She said she mainly assists with making and testing the Ni5P4 samples.

“I am constantly learning throughout this research,” she said, “Going there three or four days a week makes me so much more knowledgeable, because I am actually applying what I have learned and learning through mistakes.”

One of the challenges of the research is to obtain pure Ni5P4, since there are seven different phases that can be formed, Laursen said.

“Any little thing can easily change it from one phase to the next,” Patraju said. “It’s easy to go from one phase to another if you overheat it, or leave it for too long.”

Weini Zhang

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