What it takes to be fossil-​​free

One of my first con­ver­sa­tions here at North­eastern was with Chem­istry pro­fessor San­jeev Muk­erjee who has one ulti­mate goal for his research: “to replace all com­bus­tion related power sources with an elec­tro­chem­ical energy con­ver­sion storage system, which are cleaner, more effi­cient, and very silent.” Mukerjee’s team at the Center for Renew­able Energy Tech­nology(NUCRET) explores how elec­tro­chem­ical reac­tions can be used to meet this goal from both an energy con­ver­sion and storage perspective.

Energy stored in the chem­ical bonds of both fossil– and bio­fuels can be cleanly and effi­ciently con­verted into a use­able form without run­ning into cer­tain lim­i­ta­tions of the stan­dard com­bus­tion process. This is espe­cially impor­tant since there isn’t a lim­it­less supply of fossil fuels out there.

Only there are a couple of prob­lems that we’re all pretty familiar with these days: First, com­bus­tion has a lot of byprod­ucts (amor­phous carbon mol­e­cules) that are not good for the lungs or the envi­ron­ment. Second, there isn’t a lim­it­less supply of fossil fuels out there.

Muk­erjee is exploring better ways to break those bonds using fuel cells and better ways to store the released energy using lithium air batteries.

There’s this mis­con­cep­tion out there that we can somehow mag­i­cally create super-​​batteries that will power a car for a 300 mile range. Right now the best you can do is between 60 and 100 miles.” Con­ven­tional autos, he says, can only drive for 60–70 miles on the most advanced lithium ion bat­tery before needing to be recharged. 100 mile ranges are pos­sible when you use the lightest (and most expen­sive) com­posite mate­rials for the body. Reaching 300 miles isn’t a ques­tion of better tech­nology, it’s a ques­tion of chemistry.

The lithium air bat­tery, which was invented and patented by NUCRET’s K. M. Abraham in 1997, can work in aqueous and non-​​aqueous sys­tems, meaning it could be put to use in a variety of energy con­ver­sion and storage set­tings. The oxygen reduc­tion reac­tion in Lithium Air bat­teries works on oxygen in, well, the air (go figure). Tra­di­tional lithium-​​ion bat­teries works on the oxygen in a metal-​​oxide elec­trode, often cobalt, which is pretty expensive.

Plat­inum, as my engaged friends know, is another expen­sive metal typ­i­cally used as that cat­a­lyst in cur­rent low tem­per­a­ture fuel cell tech­nolo­gies for the oxygen reduc­tion reac­tion. Mukerjee’s team is devel­oping new cat­a­lysts that do not rely on noble metals. “We’re looking at iron nitrogen based sys­tems — trying to under­stand how the oxygen reduc­tion works in them and how you can reli­ably make it. We know it does happen, now we’re inves­ti­gating how and why it hap­pens.” While these sys­tems are still low-​​performing, the cost is orders of mag­ni­tude less than the plat­inum based system.

Ini­tially, fuel cells could be used as a stand-​​in for the com­bus­tion engine but still use fossil fuels as a source of hydrogen, nat­ural gas being the most exciting to Muk­erjee. “Between Canada and the US, there’s enough Nat­ural gas to last us a couple hun­dred years. But then there is a vast resource, which is still being looked at — gas hydrates in the ocean floor near geo­log­ical vent sites. This resource is so vast in terms of its poten­tial capacity that we’d pos­sibly never run out in 400 to 500 years.”

Still, it’s not good enough. While no renew­able energy can com­pletely replace fossil fuels right now, Muk­erjee says, we need to begin devel­oping tech­nolo­gies and busi­ness models that can even­tu­ally allow for a smooth tran­si­tion when the chem­istry and engi­neering prob­lems have been worked out.

Here you can watch Muk­erjee speak for himself: