Controlling proton source speeds catalyst in turning electricity to fuel

A new catalyst is faster when it and its surrounding acid have the same proton affinity or pKa, according to scientists at the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, at Pacific Northwest National Laboratory. The catalyst drives…

A new catalyst is faster when it and its surrounding acid have the same proton affinity or pKa, according to scientists at the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, at Pacific Northwest National Laboratory. The catalyst drives turning electrons and protons into a bond between two hydrogen atoms, storing the energy. Making the catalyst faster is vital to designing technologies that can store electrons created by wind turbines. The team’s experimental and computational studies focused on the acid that supplies the reaction’s protons. When the acid and the catalyst had the same pKa, the speed jumped from 2,400 and 27,000 hydrogen molecules a second to 4,100 to 96,000.

“This study adds a new level of understanding about how these catalysts interact with their surroundings.” said Dr. Monte Helm, an author on the study and Deputy Director of the Center. “This paper is the follow-up to our 2011 Science paper and has a lot more mechanistic details on this first-of-its-kind catalyst.”
Wind and solar energy are intermittent by nature. This fact has held them back from larger roles on the world’s energy stage. One option is to store the electricity, or electrons, inside chemical bonds, such as the one in H2. Today’s synthetic catalysts require expensive platinum, while natural catalysts are both expensive and impractical. Understanding what’s needed to design fast, efficient catalysts that rely on inexpensive metals, such as nickel, could move renewable resources to center stage.
In this study, the team synthesized a series of nickel-based electrocatalysts. These catalysts reversibly create hydrogen molecules, both storing the electrons in the bond and releasing them. Helm and his colleagues designed the original derivative in 2011. The catalysts, as confirmed by X-ray diffraction experiments, have a planar geometry and contain 7-member cyclic ligands with a single nitrogen atom. The ligands transfer the protons from the acid to the heart or active site of the catalyst, where the bonds are formed or broken.
Using supercomputers, the researchers determined the mechanics of the proton transfer from the acid to the catalyst’s active site. The supercomputers were at Environmental Molecular Sciences Laboratory at Pacific Northwest National Laboratory and the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory. When the pKa matched between the catalyst and the acid, the speed jumped.
“If you get all the pKas to match, the rates gets a lot better,” said Helm.
The researchers found that the flat or planar nature of the ligands was a factor in the catalyst’s ability to quickly transfer protons from the acid to the center. In addition, the location of the single nitrogen atom on each arm was crucial.
Helm and his colleagues at the Center for Molecular Electrocatalysis are working to reduce the energy required by the reaction while maintaining the high rate of hydrogen production. This work is part of their ongoing efforts to unlock the secrets of proton motion in catalysts.

More information: Stewart, M. et al. 2013. High Catalytic Rates for Hydrogen Production Using Nickel Electrocatalysts with Seven-Membered Cyclic Diphosphine Ligands Containing One Pendant Amine. Journal of the American Chemical Society 135(16):6033-6046. DOI: 10.1021/ja400181a

Journal reference:

Science

Journal of the American Chemical Society

Provided by

Pacific Northwest National Laboratory

view popular

5 /5 (2 votes)

Related Stories

New metal catalyst drives hydrogen fuel reaction forwards and backwards

Feb 16, 2012

(PhysOrg.com) — When it comes to driving hydrogen production, a new catalyst built at Pacific Northwest National Laboratory can do what was previously shown to happen only in nature: store energy in hydrogen and release …

Positioning and pinching slow proton movement in catalyst

Sep 20, 2011

Twisting and pinching slow a catalyst’s ability to generate energy from hydrogen, according to scientists at Pacific Northwest National Laboratory’s Center for Molecular Electrocatalysis. In converting hydrogen to electricity, …

Placing protons in right spot lets catalysts avoid wasting time, energy on profligate reactions

Feb 11, 2013

(Phys.org)—Proton delivery and removal determines if a well-studied catalyst takes its highly productive form or twists into a less useful structure, according to scientists at Pacific Northwest National …

First electricity-making catalyst to use iron to split hydrogen gas

Mar 05, 2013

A fast and efficient iron-based catalyst that splits hydrogen gas to make electricity, necessary to make fuel cells more economical, was reported by researchers at DOE’s Pacific Northwest National Laboratory. …

Recommended for you

Ceramic foam cleans up exhaust gases

Apr 25, 2013

The introduction next year of the Euro 6 exhaust-gas standard means that catalytic converters will become more expensive, above all for diesel vehicles. Empa is working on a catalytic substrate made of ceramic …

High performance semiconductor spray paint could be a game changer for organic electronics

Apr 25, 2013

Researchers at Wake Forest University’s Organic Electronics group have come up with a novel solution to one of the biggest technological barriers facing the organic semiconductor industry today. Oana Jurchescu, an assistant …

New model gives scientists guidelines to develop ‘smart’ composite materials with wrinkled microstructures

Apr 25, 2013

Many natural composite materials have evolved to wrinkle in response to certain stimuli: The eye of the squid is lined with wavy layers of silvery reflectors that give it a silvery sheen. In the cell walls of many plants, …

Geoscientists predict new compounds could change our view of what planets are made of

Apr 25, 2013

(Phys.org) —A team of researchers led by Artem R. Oganov, a professor of theoretical crystallography in the Department of Geosciences, has made a startling prediction that challenges existing chemical models …

User comments
More news stories

Study provides new evidence of cooling properties of atmospheric molecule

(Phys.org) —Scientists have discovered further evidence for the existence of new molecules in the atmosphere that have the potential to off-set global warming by reacting with airborne pollutants.

Breath study brings roadside drug testing closer

(Phys.org) —A group of researchers from Sweden have provided further evidence that illegal drugs can be detected in the breath, opening up the possibility of a roadside breathalyzer test to detect substances such as cocaine, …

Geoscientists predict new compounds could change our view of what planets are made of

(Phys.org) —A team of researchers led by Artem R. Oganov, a professor of theoretical crystallography in the Department of Geosciences, has made a startling prediction that challenges existing chemical models …

Ice tubes in polar seas—’brinicles’ or ‘sea stalactites’—provide clues to origin of life

Life on Earth may have originated not in warm tropical seas, but with weird tubes of ice—sometimes called “sea stalactites”—that grow downward into cold seawater near the Earth’s poles, scientists are …

Ceramic foam cleans up exhaust gases

The introduction next year of the Euro 6 exhaust-gas standard means that catalytic converters will become more expensive, above all for diesel vehicles. Empa is working on a catalytic substrate made of ceramic …

Microsoft brings war with Google to Kansas City

Kansas City could find itself a symbolic battleground in a national fight between Internet titans amid the debate over privacy for Web surfers. Microsoft Corp. this week launched a new advertising campaign suggesting it’s …

Can stem cells help those with arthritis?

Stems cells taken from just a few grams of body fat are a promising weapon against the crippling effects of osteoarthritis.

Review: A solar home isn’t for everyone

As someone who considers himself an environmentalist, I’d love to get a solar array for my home. But I’m finding that it may not make a lot of sense – at least right now. My wife and I drive fairly fuel-efficient cars. Our …

Teens, young adults bear disproportionate share of STDs

In the heat of the moment, it’s a good bet sexually transmitted infections are the last thing on a teen’s or young adult’s mind. Thus, according to the Centers for Disease Control and Prevention in Atlanta, young people ages …

Pilot study: Group of Bradford Co, Pa. residents concerned about health effects of hydrofracking

Residents living in areas near natural gas operations, also known as hydraulic fracturing, or fracking, are concerned their illnesses may be a result of nearby drilling operations. Twenty-two percent of the participants in …