MIT Prof. Daniel Nocera and his associates have found another formulation, based on inexpensive and widely available materials, that can efficiently catalyze the splitting of water molecules using electricity. In 2008, Nocera and his team reported developing a water-splitting catalyst that is easily prepared from earth-abundant materials (cobalt and phosphorous) and operates in benign conditions: pH neutral water at room temperature and 1 atm pressure. (Earlier post.)
In a paper published this week in the journal Proceedings of the National Academy of Science (PNAS), Nocera, along with postdoctoral researcher Mircea Dincă and graduate student Yogesh Surendranath, report finding that nickel borate can also efficiently and sustainably function as the oxygen-producing electrode for water splitting. Materials for the new catalyst are even more abundant and inexpensive than those required for the first.
Thin catalyst films with electrocatalytic water oxidation properties similar to those of a recently reported Co-based catalyst can be electrodeposited from dilute Ni2+ solutions in borate electrolyte at pH 9.2 (Bi). The Ni-Bi films can be prepared with precise thickness control and operate at modest overpotential providing an alternative to the Co catalyst for applications in solar energy conversion.
—Dincă et al.
Even more significantly, Nocera says, the new finding shows that the original compound was not a unique, anomalous material, and suggests that there may be a whole family of such compounds that researchers can study in search of one that has the best combination of characteristics to provide a widespread, long-term energy storage technology.
This could ultimately form the basis for new storage systems that would allow buildings to be completely independent and self-sustaining in terms of energy. Nocera pictures small-scale systems in which rooftop solar panels would provide electricity, with any excess going to an electrolyzer to produce hydrogen, which would be stored in tanks. When more energy was needed, the hydrogen would be fed to a fuel cell, where it would combine with oxygen from the air to form water, and generate electricity at the same time.
Nocera, the Henry Dreyfus Professor of Energy and Professor of Chemistry, says that solar energy is the only feasible long-term way of meeting the world’s ever-increasing needs for energy, and that storage technology will be the key enabling factor to make sunlight practical as a dominant source of energy. He has focused his research on the development of less-expensive, more-durable materials to use as the electrodes in devices that use electricity to separate the hydrogen and oxygen atoms in water molecules. By doing so, he aims to imitate the process of photosynthesis, by which plants harvest sunlight and convert the energy into chemical form.
The research is still in an early stage. Nocera believes that as the team carries out further research even better compounds will come to light.
Already, Nocera and his team have increased the rate of production from these catalysts a hundredfold from the level they initially reported two years ago. In addition, while the earlier paper and the new report focus on electrodes on the oxygen-producing side, originally the other electrode, which produced hydrogen, included the use of a relatively expensive platinum catalyst. But in further work, “we have totally gotten rid of the platinum of the hydrogen side,” Nocera says. “That’s no longer a concern for us,” he says, although that part of the research has not yet been formally reported.The original discovery has already led to the creation of a company, called Sun Catalytix, that aims to commercialize the system in the next two years. Nocera’s research program was recently awarded more than $4 million in funding from the US Department of Energy’s Advanced Research Projects Agency - Energy. (Earlier post.)
Mircea Dincă, Yogesh Surendranath, and Daniel G. Nocera (2010) Nickel-borate oxygen-evolving catalyst that functions under benign conditions. PNAS published ahead of print doi: 10.1073/pnas.1001859107