Can Catalysts Drive Chemical Industry Away From Fossil Feedstocks?

Published on 07 Jan, 2019

Increasing the contribution of renewable energy sources is one of the key themes in meeting the climate change goals set under Paris Agreement. Despite the push for renewable energy coming from regulators, the corporate sector and academia, the percentage of total global primary energy demand met by wind and solar energy is still under 2% (as per the 2016 IEA Report). In order to reduce the overall carbon footprint, it is important to not only address energy sources but also explore and use no/low carbon feedstock sources and technologies.

Traditionally, fossil-based sources such as coal, oil and natural gas have served as the basic building blocks for the chemical industry. However, over the last decade, significant capacity has been added for bio-based fuels and chemicals, with big players such as BASF, Dow Chemicals, Neste Oil, Solvay, and Wacker having facilities for a variety of products such as biodiesel, acetic acid, succinic acid and propylene glycol. While the underlying technologies for these products are extremely confidential due to the involvement of proprietary microorganism species, the production process is characterized by strict control and complexities associated with the specific microorganisms.

Emulating the Leaf – Artificial Photosynthesis

Of the renewable energy and feedstock approaches, one domain is increasingly attracting the attention of the corporate sector and academia – artificial photosynthesis. It emulates the billion-year old natural photosynthesis process and yields better products in terms of higher energy and value.  Analogous to the nature, artificial photosynthesis systems comprise light harvesting, charge separation, water splitting, and proton utilization to convert water into hydrogen and oxygen, and subsequently, to higher value chemicals and fuels using carbon dioxide, etc. Artificial photosynthesis can be termed as integration of photovoltaic and electrolytic systems where the photovoltaic part entails harnessing solar energy to assist in splitting water molecules under the electrolytic part. Catalysts play a crucial role in determining the system’s performance, chemical selectivity and efficiency.

Artificial photosynthesis is unique in many ways: it directly converts solar energy into valuable products by using naturally abundant water, CO2 and N2; also, without any intermediate steps, such as biomass production (as is the case with bio-based chemicals).  Unlike solar photovoltaic cells, the energy stored in artificial synthesis is in the form of chemicals such as hydrogen, sugar, and other organic materials, and can be used during rains, snowfall and other low light weather conditions. Moreover, batteries are not required to store energy. These factors give this technology a big upper hand over solar PV technology.

Current State of Development and Challenges to Overcome


Artificial photosynthesis is currently in the development stage (TRL 3–4). Research is focused on improving process efficiency, which is at around 2% vis-à-vis 5%, the threshold for commercialization. Moreover, efficiency level of 10% would be essential for the technology to compete with other solar-to-fuel technologies. For hydrogen as an output, the overall cost of production lies in the range of US$5–10 per kg, while current hydrocarbon-based feedstocks yield hydrogen at only US$2–4 per kg.

Therefore, while achieving the desired efficiency level is the foremost necessity, scaling up artificial photosynthesis from laboratory to large-scale production poses a bigger challenge. There are other important peripheral challenges as well, such as the ability to control the impact of fluctuation of sun light, portability, and ease of maintenance. These challenges can be overcome by developing economical, efficient and stable catalytic systems, an area key research groups in this field are working on. Furthermore, efficiency and cost-effectiveness can be achieved by fabricating the cellular modules in an integrated device or compact system. In this regard, nanoparticle (NP) catalyst systems could provide a solution. NP catalysts have facilitated the building of thin ‘artificial leaf’ systems based on thin-film PV cells.

Active Technology Developers

Catalytic systems for artificial photosynthesis have been of interest to companies active in fuel cell technologies, such as Toyota, Honda, Mitsubishi Motors, Toshiba, Panasonic, Evonik and SABIC. These companies have actively explored metallic, bimetallic, and transition metal oxides.

Several start-ups, such as HyperSolar, Sun Power Technologies, Green Science Alliance Co. Ltd. (part of Fuji Pigment), Quantiam Technologies Inc., Nano-x GMBH and Pixelligent, have come up with innovative catalyst systems such as plasmonic NP based on metal oxides and hydrides, surface-modified NP, and doped metals.

Outlook

Over the long term, say 2040 and beyond, while renewables (solar and wind) and bio-chemicals are expected to occupy a greater share in energy mix and feedstock, respectively, challenges associated with the two sources would need to be addressed with improved alternatives. While the development and production of batteries is expected to rise exponentially in the coming years, management of battery waste will pose a greater environmental concern (equivalent to or even higher than plastic pollution). Also, batteries may not be an attractive option for industries such as aviation and marine, where solar fuels could be a better fit. To effectively achieve the sustainability goals of technologies such as fuel cells, fuel hydrogen must be ‘green’, not ‘brown’.

Developing high performance, yet cost-effective catalyst systems, shall be the key in addressing the techno-commercial challenges associated with artificial photosynthesis. At the same time, technology developers would do well to focus on effective component integration in miniaturized devices. Nanoparticles have exhibited considerable potential in increasing process efficiency and making devices ‘thinner’.

Innovation and R&D groups active in developing catalyst technologies must consider artificial photosynthesis catalysts and include these in their future technology roadmaps. There are plenty of opportunities for collaborating with emerging start-ups and universities in this field. An effective strategy encompassing synergistic collaborations and innovative technology backed by IP protection shall be instrumental for becoming a technology leader in the future zero-carbon economy.




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