Imagine rolling down the street in a brand-new convertible, secure in the knowledge that your latest extravagance is powered by renewable hydrogen fuel cells. Now consider the terrible implications if the hydrogen cannot be stored safely. Hydrogen in its pure form is an exceedingly reactive gas that must be kept at extreme pressures and temperatures not safe using traditional metal or plastic containers. Developing a light, low-cost receptacle that can withstand these conditions is the work of Sarah Cryer '10 (Stamford, Conn.) under the advisement of Assistant Professor of Chemistry Camille Jones.
Cryer and Jones are part of a team looking at semiclathrate – a compound composed of complex ring structures of hydrogen, ammonium, and oxygen – that Cryer says to "think about like ice with salt in it." However, the "salt" is not your ordinary table salt, but rather one of a selection of complex ammonium-based salt crystals. Different forms of semiclathrate can be formed by using different salts, a process aided greatly by computer modeling, which Cryer describes as "most of what we do, since it's very important to get that right." Another part of the team's activity is synthesizing the semiclathrate, a three-step process that can take weeks to get right, and determining its purity by using X-ray diffraction, a process that gives a series of peaks showing different functional groups within the molecule.
Once a suitable form of semiclathrate has been accurately modeled and synthesized, the trick is to fill in "empty cages" in the structure. "The semiclathrate is formed of bonds that make spaces called 'cages,'" explains Cryer. "Some of the cages are filled by the ammonium salt, but others need a 'guest molecule.' Part of the challenge is to find a stable guest molecule." Guest molecules are usually epoxides or more complex carbon-chain ring structures. These molecules are synthesized by a partnering team under the advisement of Assistant Professor of Chemistry Ian Rosenstein, and the prospective guest molecules are then passed on to the Jones lab to be tested for viability.
"If a guest molecule is too large for the cages, the whole structure will collapse, but sometimes bigger guest molecules make stronger structures than smaller ones," says Cryer. "If the molecule is too small, the structure won't be stable. The guest molecules will be combined with the semiclathrate as liquids, and can then be molded into any shape desired, similar to creating a complicated ice cube.
Despite this amazing malleability, the semiclathrate compounds can withstand extreme temperatures and pressures – possibly even those necessary to hold compressed hydrogen. The semiclathrate samples will be tested for durability, melting point, and other key characteristics to determine whether a form of semiclathrate could eventually be used to replace our gas tanks. Cryer points out the process is far from completion and could take years, but Jones is quick to point out that, "there is a distinct possibility of achieving great results."
Cryer is an active student in the Hamilton Chemistry Department who, although "not 100 percent sure" of her future plans, is excited about following up this summer's research with further efforts. When not trying to revolutionize the fuel economy of the United States in the Science Center, Cryer can often be found burning a different kind of energy in a very different place: calories in the Bristol Pool. She is a valuable and enthusiastic member of Hamilton's swim team, swimming the women's 50m freestyle and anchoring one of the Hamilton women's 200m freestyle relay teams.
-- by Elijah Lachance '10
Cryer and Jones are part of a team looking at semiclathrate – a compound composed of complex ring structures of hydrogen, ammonium, and oxygen – that Cryer says to "think about like ice with salt in it." However, the "salt" is not your ordinary table salt, but rather one of a selection of complex ammonium-based salt crystals. Different forms of semiclathrate can be formed by using different salts, a process aided greatly by computer modeling, which Cryer describes as "most of what we do, since it's very important to get that right." Another part of the team's activity is synthesizing the semiclathrate, a three-step process that can take weeks to get right, and determining its purity by using X-ray diffraction, a process that gives a series of peaks showing different functional groups within the molecule.
Once a suitable form of semiclathrate has been accurately modeled and synthesized, the trick is to fill in "empty cages" in the structure. "The semiclathrate is formed of bonds that make spaces called 'cages,'" explains Cryer. "Some of the cages are filled by the ammonium salt, but others need a 'guest molecule.' Part of the challenge is to find a stable guest molecule." Guest molecules are usually epoxides or more complex carbon-chain ring structures. These molecules are synthesized by a partnering team under the advisement of Assistant Professor of Chemistry Ian Rosenstein, and the prospective guest molecules are then passed on to the Jones lab to be tested for viability.
"If a guest molecule is too large for the cages, the whole structure will collapse, but sometimes bigger guest molecules make stronger structures than smaller ones," says Cryer. "If the molecule is too small, the structure won't be stable. The guest molecules will be combined with the semiclathrate as liquids, and can then be molded into any shape desired, similar to creating a complicated ice cube.
Despite this amazing malleability, the semiclathrate compounds can withstand extreme temperatures and pressures – possibly even those necessary to hold compressed hydrogen. The semiclathrate samples will be tested for durability, melting point, and other key characteristics to determine whether a form of semiclathrate could eventually be used to replace our gas tanks. Cryer points out the process is far from completion and could take years, but Jones is quick to point out that, "there is a distinct possibility of achieving great results."
Cryer is an active student in the Hamilton Chemistry Department who, although "not 100 percent sure" of her future plans, is excited about following up this summer's research with further efforts. When not trying to revolutionize the fuel economy of the United States in the Science Center, Cryer can often be found burning a different kind of energy in a very different place: calories in the Bristol Pool. She is a valuable and enthusiastic member of Hamilton's swim team, swimming the women's 50m freestyle and anchoring one of the Hamilton women's 200m freestyle relay teams.
-- by Elijah Lachance '10
