| Materials

Dr. Haimei Zheng, Staff Scientist, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA

Dr. Zheng and her team of scientists from Berkeley Lab and Nanyang Technical University in Singapore made metal-organic spongy photocatalysts that convert carbon dioxide (CO2) to carbon monoxide (CO) in the presence of sunlight. They were able to make liquid fuels with the noble nanoparticle-decorated spongy material.

Tech Briefs: With this work, were you trying to improve on an existing process?

Dr. Haimei Zheng: There are not many catalysts for the job right now. Currently, to do this conversion, you can use high temperature and high energy; however, only a few materials can do the conversion effectively, and not with high selectivity or on the scale we’d like to achieve. I don’t see an attractive industry-scale technology for this yet.

Tech Briefs: Have your experiments been successful?

Dr. Zheng: As I said, we were trying to develop a new catalyst. Although there are so many people working on new catalysts, we believe our approach is unique. We use a laser as the energy source in order to produce a nickel-organic photocatalyst similar to a metal-organic framework (MOF). Our initial idea was to use a laser system as a source because it might trigger fast nucleation, while growth at room temperature might be suppressed. Due to the non-equilibrium growth process, the materials might not be perfect. However, materials with defective structures could be perfect for catalysis. This was a simple idea to try. Although we’ve already been making catalysts with this method, this is the first time we made it for CO2 reduction.

Tech Briefs: What are some key aspects of your process?

Dr. Zheng: There are two steps in our research effort. First, we make the catalyst using an infrared laser as a source to irradiate a molecular precursor solution. In this way, spongy metal-organic catalysts can be synthesized by means of a photo-chemical reaction. The second step is to do the photocatalysis for the CO2 reduction reaction. So far, the material itself does not absorb visible light, so when we do the reaction, we add a photosynthesizer that absorbs the photons and generates the electrons needed for the photocatalytic reaction.

Tech Briefs: Have you been successful in generating CO from CO2?

Dr. Zheng: We were able to use novel catalysts to convert CO2 to CO with 100% selectivity of carbon monoxide over other gases. It is of great importance that we overcame the challenge of suppressing the evolution of hydrogen or other gases as byproducts.

Tech Briefs: How soon could this evolve into a practical industrial process?

Dr. Zheng: The Joint Center for Artificial Synthesis (JCAP), a collaboration between Berkeley and Caltech, has a mission to produce liquid fuels. I think we have made a huge step forward in that direction. It has been exciting for us to make catalysts with high efficiency and high selectivity. Our very next step will focus on improving the material synthesis, which we could do in the short term.

As scientists, we don’t have the answer as to when this could become an industrial reality — there are other factors. We have a provisional patent, and I hope someone will be interested in implementing this on an industrial scale.

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