Copper - the stuff of pennies and tea kettles - is also one of the f ...

Copper - the stuff of pennies and tea kettles - is also one of the few metals that can turn carbon dioxide (CO2) into hydrocarbon fuels with relatively little energy. When fashioned into an electrode and stimulated with voltage, copper acts as a strong catalyst, setting off an electrochemical reaction with CO2 that reduces the greenhouse gas to methane or methanol. Various researchers around the world have studied copper’s potential as an energy-efficient means of recycling CO2 emissions in power plants. Instead of being released into the atmosphere, CO2 would be circulated through a copper catalyst and turned into methane - which could then power the rest of the plant. Such a self-energising system could vastly reduce greenhouse gas emissions from coal-fired and natural-gas-powered plants. However, copper is temperamental and easily oxidised, as when an old penny turns green. As a result, the metal is unstable, which can significantly slow its reaction with CO2 and produce unwanted byproducts such as carbon monoxide and formic acid. Now researchers at MIT have come up with a solution that may further reduce the energy needed for copper to convert CO2, while also making the metal much more stable. The group has engineered tiny nanoparticles of copper mixed with gold, which is resistant to corrosion and oxidation. The researchers observed that just a touch of gold makes copper much more stable. In experiments, they coated electrodes with the hybrid nanoparticles and found that much less energy was needed for these engineered nanoparticles to react with CO2, compared to nanoparticles of pure copper. A paper detailing the results will appear in the journal Chemical Communications; the research was funded by the National Science Foundation. Co-author Kimberly Hamad-Schifferli of MIT says the findings point to a potentially energy-efficient means of reducing CO2 emissions from power plants. ‘You normally have to put a lot of energy into converting carbon dioxide into something useful,’ says Hamad-Schifferli, an associate professor of mechanical engineering and biological engineering. ‘We demonstrated hybrid copper-gold nanoparticles are much more stable, and have the potential to lower the energy you need for the reaction.’ Going forward, Hamad-Schifferli says she hopes to look more closely at the structure of the gold-copper nanoparticles to find an optimal configuration for converting CO2. So far, the team has demonstrated the effectiveness of nanoparticles composed of one-third gold and two-thirds copper, as well as two-thirds gold and one-third copper. She acknowledges that coating industrial-scale electrodes partly with gold can get expensive. However, she claims the energy savings and the reuse potential for such electrodes may balance the initial costs.