The Catalyst Review August 2019 - 7

INDUSTRY PERSPECTIVES

The views expressed are those of the individual author and may not reflect those of The Catalyst Review or TCGR
Industry Perspectives (continued from page 1)

additional economic benefit if O2 is collected and placed on the market. For a full exploitation of such technology, improvements
of electrolysis are necessary, from long-life and more powerful electrolysers, to developing electrolysis under pressure so to have
pressurized H2 for an immediate use in industrial applications, to high temperature (solid-state) electrolysis for energy minimization.
PV-electrons could be used in driving direct electrochemical syntheses avoiding the use of fossil-C and the relevant environmental
impact. Such approach is particularly useful for some organic products. The surface of the electrode may play a key role in addressing
the selectivity of a process towards a given product. For example, copper electrodes in the reduction of CO2 in water favor the
formation of ethene, non soluble in water, with respect to other reduction products (Aresta et al. 2018). Ethene would be used for
making polymers. Even the synthesis of methanol by electroreduction would be of interest, as it would open to value-chains bringing
to ethene, propene, DME, formaldehyde, and polymers such as polyethene, polypropene, formaldehyde resins.
Photoelectrochemical processes combine the use of electrodes made of photo-materials with redox reactions: the irradiation of
electrodes with solar light would allow the generation of an electron flow that may selectively drive chemical reactions. Reactions
may occur at the electrode surface (in this case the nature of the electrode would drive the process-selectivity) or on electro-catalysts
either attached to the electrode surface or present in solution nearby the electrode surface. The latter option would affect less the
electrode surface assuring a longer life. In bio-electrochemical and photo-bio-electrochemical processes either PV-electrons or photogenerated electrons are injected into enzymes or bio-systems supported on electrodes for boosting syntheses of specific chemicals,
according to the biocatalyst used (Schlager et al. 2017). Such processes are of interest for boosting the ability of bio-systems to
produce selectively some chemicals by increasing the reducing power represented by electrons or hydrogen. Such applications may
greatly help to substitute fossil C with CO2, implementing the Circular Economy concept. The great advantage of fossil-C is that it
remains the most concentrated form of solar energy and thus is much more intensive than other solar driven processes. Natural
evolution has optimized the function of molecules rather than the energetic efficiency (plentiful energy is available). Catalytic
technologies minimize the activation barriers and thus optimize the energetic efficiencies. The target of man-made proficient use of
solar energy is the intensification of its application competing with bio-systems in efficiency and selectivity towards a single product.
An example of such approach is the enhanced microalgae cultivation in photo-bioreactors (PBR) reaching solar light efficiencies
higher (>12-13%) than natural systems (5-8%). Genetic manipulation of strains or stressing cultures by starvation of N or P nutrients
may bring to increased yields of lipids containing selected fatty acids (Aresta et al. 2016). The integration of biotechnologies and
catalysis (Aresta et al. 2016) may bring to the development of processes that recycle large volumes of carbon in the form of CO2
complementing Nature and avoiding the use of fossil-C.
References
Aresta M, Nocito F and Dibenedetto A. (2018). "What Catalysis Can do for Boosting CO2 Utilization." Advances in Catalysis. DOI:
10.1016/bs.acat.2018.08.002.
Aresta M, Dibenedetto A and Quaranta E. (2016). Chapter 9 in "Reaction Mechanisms in Carbon Dioxide Conversion." Springer.
Schlager S, Dibenedetto A, Aresta M, et al. (2017). "Biocatalytic and Bioelectrocatalytic Approaches for the Reduction of Carbon
Dioxide Using Enzymes." Energy Technol, 2017, 5: 1-11.
About the Author
Michele Aresta holds a doctorate in Industrial Chemistry at the University of Milan-IT and is a full Professor of Inorganic Chemistry
at the University of Bari, an Honorary Professor of the Tianjin University, and is currently with NUS Singapore, ChBE Deaprtment.
He is President of the Inorganic Chemistry Division of Italian Chemical Society and Director of the "Interuniversity Consortium on
Chemical Reactivity and Catalysis." His areas of research are carbon dioxide utilization in synthetic chemistry, catalysis, coordination
and metallorganic chemistry. Professor Aresta is author of more than 200 papers and editor of four books. He has received several
awards, like the Award of the Italian Chemical Society and the Prize of the société française de Chimie for Inorganic Chemistry. He can
be reached at cheam@nus.edu.sg.

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