(414c) Design of Autonomous Multifunctional GaN:ZnO Based Photocatalysts for Artificial Photosynthesis | AIChE

(414c) Design of Autonomous Multifunctional GaN:ZnO Based Photocatalysts for Artificial Photosynthesis


Matsubu, J. C. - Presenter, University of California, Riverside
Christopher, P., University of California, Santa Barbara

The global reliance on fossil fuels as a primary energy source is unsustainable due to massive CO2 emissions. An extremely appealing solution is to develop Artificial Photosynthesis (AP) technologies that utilize solar energy to drive the conversion of water and negatively valued CO2 into positively valued chemicals and fuels. Previous research in this field has focused on photocatalytic AP reactions at near ambient conditions, high temperature dissociation of H2O and CO2 through metal-oxide looping, or photoelectrochemical approaches. These approaches are limited by low rates, high temperatures, and/or complicated and expensive process design.

 We will discuss an approach that exploits full solar spectrum conversion to split water and reduce CO2 at moderate temperatures on autonomous multifunctional materials. The hypothesis driving this work is that a single material can be designed that utilizes high-energy photons to drive the endothermic water splitting reaction and low energy photons to heat the catalyst and drive the exothermic CO2 reduction process.  Multifunctional catalysts are designed by combining autonomous GaN and ZnO based water-splitting photocatalysts with co-catalysts for thermocatalytic CO2 reduction.

We have explored the effect of co-catalyst metal type and oxidation state, CO2:H2 ratio, reaction temperature, and light intensity on thermocatalytic CO2 reduction. We tested various GaN:ZnO supported methanation co-catalysts (Ni, Ru, Rh and their oxide counterparts) for their ability to drive CO2 reduction and suppress oxidation back reactions. Results have shown a difference in catalytic activity and selectivity for CO2 reduction based on co-catalyst composition, oxidation state, and CO2:H2 feed ratio. In addition, an increase in activity of CO2 reduction was observed in the presence of light at elevated temperatures. These results will be discussed in the context of designing an overall H2O and CO2 conversion process based on autonomous, multifunctional materials.