TY - BOOK

T1 - High-Entropy Alloys for Catalysis

T2 - Theoretical modeling and catalyst discovery

AU - Pedersen, Jack Kirk

PY - 2021

Y1 - 2021

N2 - New catalysts are needed more than ever. This is because our societyis facing an inevitable transition away from fossil fuels as a source ofenergy and carbon-based commodity chemicals. Carbon derived from fossilfuels is used to manufacture many products in everyday life, including fuels,plastic, and medicine. New sources of the elements needed by society willhave to take the place of fossil fuels. Most likely, this will include extractinghydrogen from water as well as capture and conversion of carbon dioxideto precursor chemicals. The energy for these processes must likewise be derivedfrom sustainable sources. With regard to this, efficient energy storageand release of sustainable, intermittent energy is needed.The success of all of the above scenarios highly depends on the ability tocatalyze the chemical reactions involved. Without catalysis, the cost of theenergy involved in these processes will become insurmountable. Unfortunately,suggesting a suitable material to use as the catalyst is not straightforward.The aim of this thesis is to show that a new class of materials, namelyhigh-entropy alloys, provides a way to design new materials with desired andhighly tunable properties.High-entropy alloys are metallic materials containing five or more metalsin about the same proportions. The number of ways to combine metalsfrom the periodic table and form variants of these materials is exceedinglylarge. This is both an advantage and a complicating factor of high-entropyalloys. While the complexity associated with predicting the catalytic propertiesis increased compared to the pure metals, it is precisely this complexitythat allows for unconventional properties to show.This thesis describes how successful modeling of the surfaces of high-entropyalloys can be achieved. It also shows how models can assist in solving theproblem of suggesting catalysts for two of the reactions alluded to above,namely (1) the conversion of hydrogen and oxygen to water for the releaseof stored intermittent energy, and (2) the conversion of carbon dioxide intouseful chemicals. Moreover, a highly transferable methodology for tuningthe compositions of high-entropy alloys favorably is demonstrated.There still remain investigations to be done before high-entropy alloys canbe upscaled to large-scale use. In particular, a satisfactory theory remains tobe constructed that allows for the simultaneous prediction of catalytic activity,long-term stability, as well as chemical selectivity of high-entropy alloys.This theory should at least be valid for the cornerstone chemical reactionsneeded to realize a sustainable future.

AB - New catalysts are needed more than ever. This is because our societyis facing an inevitable transition away from fossil fuels as a source ofenergy and carbon-based commodity chemicals. Carbon derived from fossilfuels is used to manufacture many products in everyday life, including fuels,plastic, and medicine. New sources of the elements needed by society willhave to take the place of fossil fuels. Most likely, this will include extractinghydrogen from water as well as capture and conversion of carbon dioxideto precursor chemicals. The energy for these processes must likewise be derivedfrom sustainable sources. With regard to this, efficient energy storageand release of sustainable, intermittent energy is needed.The success of all of the above scenarios highly depends on the ability tocatalyze the chemical reactions involved. Without catalysis, the cost of theenergy involved in these processes will become insurmountable. Unfortunately,suggesting a suitable material to use as the catalyst is not straightforward.The aim of this thesis is to show that a new class of materials, namelyhigh-entropy alloys, provides a way to design new materials with desired andhighly tunable properties.High-entropy alloys are metallic materials containing five or more metalsin about the same proportions. The number of ways to combine metalsfrom the periodic table and form variants of these materials is exceedinglylarge. This is both an advantage and a complicating factor of high-entropyalloys. While the complexity associated with predicting the catalytic propertiesis increased compared to the pure metals, it is precisely this complexitythat allows for unconventional properties to show.This thesis describes how successful modeling of the surfaces of high-entropyalloys can be achieved. It also shows how models can assist in solving theproblem of suggesting catalysts for two of the reactions alluded to above,namely (1) the conversion of hydrogen and oxygen to water for the releaseof stored intermittent energy, and (2) the conversion of carbon dioxide intouseful chemicals. Moreover, a highly transferable methodology for tuningthe compositions of high-entropy alloys favorably is demonstrated.There still remain investigations to be done before high-entropy alloys canbe upscaled to large-scale use. In particular, a satisfactory theory remains tobe constructed that allows for the simultaneous prediction of catalytic activity,long-term stability, as well as chemical selectivity of high-entropy alloys.This theory should at least be valid for the cornerstone chemical reactionsneeded to realize a sustainable future.

M3 - Ph.D. thesis

BT - High-Entropy Alloys for Catalysis

PB - Department of Chemistry, Faculty of Science, University of Copenhagen

ER -