Salt + H2O - CO2 = Electricity + H2
Most of us are probably at least noddingly familiar with fuel cells, since they were widely touted by NASA for their applications in space craft and satellites. Some of us in the HVAC industry may even be using forklifts running on fuel cells. And there are also fuel cell-powered cars and buses out there.
However, many experts – including such luminaries as Elon Musk, who calls them “fool cells” – believe that their applications are limited by the cost of producing hydrogen, which most fuel cells rely on, and the danger of transporting hydrogen due to its flammability (See, 'Hindenburg'). Typically, a fuel cell uses hydrogen and oxygen in an electrochemical reaction to generate electricity, with water as the byproduct. When hydrogen is burned with oxygen, it’s a zero-emission “clean” fuel.
Now researchers at the Ulsan National Institute of Science and Technology (UNIST) in South Korea have developed a new type of electrochemical cell that produces electricity with hydrogen as its byproduct, and eliminates CO2, the worst offender in global warming. Known as the Hybrid Na-CO2 System, the UNIST cell has the same major components as does a fuel cell: a cathode, an anode, and an electrolyte. In a fuel cell, the cathode is the negative pole of the fuel cell, and conducts electrons from the hydrogen molecules that are used in the external electrical circuit. It also disperses the hydrogen on the surface of the catalyst. The cathode is the positive pole of the fuel cell, and both distribute the oxygen to the surface of the catalyst and conducts the electrons back from the external electrical circuit to the catalyst, where they recombine with the hydrogen ions and oxygen to form water.
In the Hybrid Na-CO2 cell, the cathode is contained in an aqueous solution and the sodium (Na) metal anode is submersed in an organic electrolyte. The two solutions are separated by what the team calls a Sodium Super Ionic Conductor or NASICON. When CO2 is injected into the water solution, the ensuing electrochemical reaction eliminates the CO2 and produces both electricity and hydrogen. According to the researchers, CO2 conversion efficiency is currently 50 percent, which is considered high.
Since I live at the beach, it’s not surprising that I’m a strong proponent for desalination. If it can be done economically, it has the potential to solve a lot of problems, especially the need for fresh water in underdeveloped coastal countries. If the Hybrid Na-CO2 cell can be commercially produced, desalinated sea water could provide both the salt and the water needed for it to operate. This could provide portable electricity, while simultaneously reducing carbon footprint and producing hydrogen for use as a fuel. That would surely be a win-win, even for climate change skeptics!
A regular contributor to HPAC Engineering and a member of its editorial advisory board, the author is a principal at Sustainable Performance Solutions LLC, a south Florida-based engineering firm focusing on energy and sustainability.