Product selectivity in plasmonic photocatalysis for carbon dioxide hydrogenation
Approximately 80% of the processes in the chemical industries require the use of catalysts. Most catalytic processes are heterogeneous in nature, and require a high operating temperature to overcome the large activation energy and perform reactions at practical rates. The high operating temperature not only demands high thermal energy input, but also deteriorates the catalyst lifetime due to the sintering of catalyst nanoparticles. Ideal catalysts simultaneously lower operating temperatures, accelerate reaction rates, and preferentially select products without being consumed or altered. In spite of extensive research on this subject, no photocatalyst has yet achieved this lofty objective.
A recent demonstration by Duke may have found a solution to this problem. It is shown that light can control product selectivity in complex chemical reaction. This selectivity, the ability to control the chemical reaction so that it generates the desired product with little or no side-products, is an important factor in determining the cost and feasibility of industrial-scale reactions. In particular, it is shown that plasmonic rhodium (Rh) nanoparticles are photocatalytic, simultaneously lowering activation energies and exhibiting strong product photo-selectivity, as illustrated through the CO2 hydrogenation reaction. Methane is almost exclusively produced when Rh nanoparticles are mildly illuminated as hot electrons are injected into the anti-bonding orbital of a critical intermediate, while carbon monoxide and methane are equally produced without illumination. The reduced activation energy and super-linear dependence on light intensity cause the unheated photocatalytic methane production rate to exceed the thermocatalytic rate at 400°C. In a more general aspect, using light together with heat open a new possibility that is different from pure thermal and pure photo catalytic process.
Solar powered, renewable energy systems with applications in:
- Carbon dioxide hydrogenation to Methane
- Emission control
- Ammonia oxidation reaction
- Carbon Monoxide oxidation at low temeprature
US Patent Pending
Zhang, X. et al. Product selectivity in plasmonic photocatalysis for carbon dioxide hydrogenation. Nat. Commun. 8, 14542 doi: 10.1038/ncomms14542 (2017).
George Barth Geller Professor of Chemistry in Trinity College of Arts and Sciences