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Developing Methods to Inform Catalys...

Boyd, Michael James.

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Developing Methods to Inform Catalyst Design for the Electrochemical Oxidation of Methane and Alcohols.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Developing Methods to Inform Catalyst Design for the Electrochemical Oxidation of Methane and Alcohols./
作者:	Boyd, Michael James.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
面頁冊數:	126 p.
附註:	Source: Dissertations Abstracts International, Volume: 82-10, Section: B.
Contained By:	Dissertations Abstracts International82-10B.
標題:	Catalytic oxidation. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28330440
ISBN:	9798597039893

Developing Methods to Inform Catalyst Design for the Electrochemical Oxidation of Methane and Alcohols.
Boyd, Michael James.

Developing Methods to Inform Catalyst Design for the Electrochemical Oxidation of Methane and Alcohols. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 126 p.

Source: Dissertations Abstracts International, Volume: 82-10, Section: B.

Thesis (Ph.D.)--Stanford University, 2020.

This item must not be sold to any third party vendors.

As the production of natural gas and agricultural biomass/energy crops increases, new efficient and sustainable technologies will be required to convert these feedstock molecules into the same fuels and chemical we get from conventional petroleum today. Electrochemistry is a possible tool for the conversion of these species that can be coupled to renewable electricity. The discovery and development of selective and active electrocatalysts is one of the primary challenges in utilizing natural gas and biomass resources. But first there is a lack of fundamental understanding in (1) the reaction mechanism and (2) how operating conditions such as potential, electrolyte pH, mass transport, and time affect the the activity and selectivity of catalysts. To this end platinum was used as a model system to study electrochemical methane oxidation at room temperature and pressure. The experimental results on platinum combined with density functional theory calculations show that methane is first thermally activated at Pt (211) like step sites, then the resulting methyl intermediate is electrochemically oxidized to CO* which is in equilibrium with the final product CO2. The equilibrium can be shifted to favor complete oxidation by adjusting the applied electrochemical potential, specifically at potentials below 0.5 V vs. RHE CO* is the most thermodynamically stable species along the reaction pathway whereas above 0.5 V vs. RHE CO2 is now the most stable species. Important to note however is that since the kinetics for methane activation are very slow (barrier of ~0.95 eV) the platinum surface must be free of other adsorbed species, namely protons or hydroxides. Based on reaction mechanism for electrochemical methane oxidation on platinum it is unlikely that partial oxidation of methane on metallic electrodes well occur. For this reason we probed the activity of several transition metal oxide materials with the hope that they may be active for methane oxidation. Unfortunately our initial results suggest no significant methane oxidation occurs on these materials. In the case of biomass oxidation 1st row transition metal oxides have recently been shown to be quite selective in the conversion of alcohols to their corresponding carboxylic acids. Benzyl alcohol was used as a model molecule to study the reaction mechanism for alcohol oxidation on Ni(OH)2 electrodes as a function of potential and electrolyte pH. It was found that the active phase for alcohol oxidation is the metal oxy-hydroxide. The activity and selectivity were found to be heavily dependent on the electrolyte pH. Under strong alkaline conditions (> pH 13) high current densities and complete oxidation of benzyl alcohol to benzoate was favored whereas at more moderately alkaline conditions low current densities and partial oxidation to benzaldehyde was favored. Based on these results we hypothesize that a significant concentration of OH- in solution is required to activated the intermediate product benzaldehyde. The activity of several novel Ni materials was also probed for benzyl alcohol oxidation. Ni-doped nitrided carbons which have single atom nickel active sites were found to be selective for partial oxidation, however further optimization of the catalyst synthesis is required to increase the activity to compete with the bulk Ni(OH)2 electrodes. In conclusion, this dissertation presents a variety of experimental work focused on identifying the reaction mechanism for several oxidation reactions and provides key understanding that can be used towards the development of new electrocatalysts for the oxidation of hydrocarbons and alcohols.

ISBN: 9798597039893Subjects--Topical Terms:

3560642
Catalytic oxidation.
Subjects--Index Terms:

Renewable electricity

Developing Methods to Inform Catalyst Design for the Electrochemical Oxidation of Methane and Alcohols.
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506 $a This item must not be sold to any third party vendors.
520 $a As the production of natural gas and agricultural biomass/energy crops increases, new efficient and sustainable technologies will be required to convert these feedstock molecules into the same fuels and chemical we get from conventional petroleum today. Electrochemistry is a possible tool for the conversion of these species that can be coupled to renewable electricity. The discovery and development of selective and active electrocatalysts is one of the primary challenges in utilizing natural gas and biomass resources. But first there is a lack of fundamental understanding in (1) the reaction mechanism and (2) how operating conditions such as potential, electrolyte pH, mass transport, and time affect the the activity and selectivity of catalysts. To this end platinum was used as a model system to study electrochemical methane oxidation at room temperature and pressure. The experimental results on platinum combined with density functional theory calculations show that methane is first thermally activated at Pt (211) like step sites, then the resulting methyl intermediate is electrochemically oxidized to CO* which is in equilibrium with the final product CO2. The equilibrium can be shifted to favor complete oxidation by adjusting the applied electrochemical potential, specifically at potentials below 0.5 V vs. RHE CO* is the most thermodynamically stable species along the reaction pathway whereas above 0.5 V vs. RHE CO2 is now the most stable species. Important to note however is that since the kinetics for methane activation are very slow (barrier of ~0.95 eV) the platinum surface must be free of other adsorbed species, namely protons or hydroxides. Based on reaction mechanism for electrochemical methane oxidation on platinum it is unlikely that partial oxidation of methane on metallic electrodes well occur. For this reason we probed the activity of several transition metal oxide materials with the hope that they may be active for methane oxidation. Unfortunately our initial results suggest no significant methane oxidation occurs on these materials. In the case of biomass oxidation 1st row transition metal oxides have recently been shown to be quite selective in the conversion of alcohols to their corresponding carboxylic acids. Benzyl alcohol was used as a model molecule to study the reaction mechanism for alcohol oxidation on Ni(OH)2 electrodes as a function of potential and electrolyte pH. It was found that the active phase for alcohol oxidation is the metal oxy-hydroxide. The activity and selectivity were found to be heavily dependent on the electrolyte pH. Under strong alkaline conditions (> pH 13) high current densities and complete oxidation of benzyl alcohol to benzoate was favored whereas at more moderately alkaline conditions low current densities and partial oxidation to benzaldehyde was favored. Based on these results we hypothesize that a significant concentration of OH- in solution is required to activated the intermediate product benzaldehyde. The activity of several novel Ni materials was also probed for benzyl alcohol oxidation. Ni-doped nitrided carbons which have single atom nickel active sites were found to be selective for partial oxidation, however further optimization of the catalyst synthesis is required to increase the activity to compete with the bulk Ni(OH)2 electrodes. In conclusion, this dissertation presents a variety of experimental work focused on identifying the reaction mechanism for several oxidation reactions and provides key understanding that can be used towards the development of new electrocatalysts for the oxidation of hydrocarbons and alcohols.
590 $a School code: 0212.
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650 4 $a Physical chemistry. $3 1981412
650 4 $a Biomass. $3 1013462
650 4 $a Hydrocarbons. $3 697428
650 4 $a Catalysis. $3 560465
650 4 $a Carbon dioxide. $3 587886
650 4 $a Adsorption. $3 580046
653 $a Renewable electricity
653 $a Electrocatalysts
653 $a Feedstocks
653 $a Biofuels
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793 $a English
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