Electrochemical Carbon Dioxide Reduction for Renewable Carbonaceous Fuels and Chemicals
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Electrochemical CO2 reduction reaction (ECO2RR) powered by renewable electricity possesses the potential to store intermittent energy in chemical bonds while producing sustainable chemicals and fuels. Unfortunately, it is hard to achieve low overpotential, high selectivity, and activity simultaneously of ECO2RR. Developing efficient electrocatalysts is the most promising strategy to enhance electrocatalytic activity in CO2 reduction. Herein, we designed novel Bi-Cu2S heterostructures by a one-pot wet-chemistry method. The epitaxial growth of Cu2S on Bi results in abundant interfacial sites and these heterostructured nanocrystals demonstrated high electrocatalytic performance of ECO2RR with high current density, largely reduced overpotential, near-unity FE for formate production (Chapter 2). Meanwhile, we see a lot of opportunities for catalysis in a confined space due to their tunable microenvironment and active sites on the surface, leading to a broad spectrum of electrochemical conversion schemes. Herein, we reveal fundamental concepts of confined catalysis by summarizing recent experimental investigations. We mainly focus on carbon nanotubes (CNTs) encapsulated metal-based materials and summarize their applications in emerging electrochemical reactions, including ECO2RR and more (Chapter 3). Although we were able to obtain high activity and selectivity toward C1 products, it is more attractive to go beyond C1 chemicals to produce C2 products due to their high industrial value. Herein, we designed Ag-modified Cu alloy catalysts that can create a CO-rich local environment for enhancing C-C coupling on Cu for C2 formation. Moreover, Ag corporate in Cu can chemically improve the structural stability of Cu lattice. (Chapter 4) Nevertheless, advanced electrocatalytic platforms cannot be developed without a fundamental understanding of binding configurations of the surface-adsorbed intermediates and adsorbate-adsorbate interaction on the local environment in electrochemical CO2 reduction. In this case, we make discussions of recent developments of machine learning based models of adsorbate-adsorbate interactions, including the oversimplified linear analytic relationships, the cluster expansion models parameterized by machine learning algorithms, and the highly nonlinear deep learning models. We also discuss the challenges of the field, particularly overcoming the limitations of pure data driven models with the integration of computational theory and machine learning of lateral interactions for catalyst materials design. (Chapter 5).
General Audience Abstract
Excessive CO2 emissions into the atmosphere have had severe environmental impacts and pose an urgent and potentially irreversible threat to human activity. Fossil fuels, including coal, oil, and natural gas, have continued to play a dominant role in the global energy system. However, fossil fuels produce substantial greenhouse gases, which are the main contributor to global warming. This year, the global average CO2 level is increasing to 413.6 parts per million, higher than at any point in the past hundred years. To address this global warming issue, we see lots of opportunities to use alternative energy sources to convert atmospheric CO2 into value-added products through the electrochemical reduction of CO2. Nevertheless, advanced electrocatalytic platforms cannot be developed without efficient electrocatalysts in the reaction system. Therefore, we have been working on the design of catalysts with various features that improve the electrochemical reduction of CO2. The interface plays an important role as the reactions are happening at the active sites which mostly locate at the interface of electrocatalysts. We designed a novel Bi-Cu2S hetero-structured catalyst, which has abundant interfacial sites between Bi and Cu2S, demonstrating the improved catalytic performance of ECO2RR toward formate production (Chapter 2). Catalysis in a confined space offers another opportunity for tuning the catalytic performance, where carbon nanotubes (CNTs) encapsulated metal-based materials have been shown to increase the reactivity of electrochemical reactions, including ECO2RR and more (Chapter 3). Interfaces in alloys provide multifunctional environments which have been shown to have reactivity toward complicated reactions. To produce more value-added C2 chemicals, Ag-modified Cu alloy catalysts are developed, which can create a CO-rich local environment for enhancing C-C coupling on Cu to enhance C2 formation (Chapter 4). To develop advanced electrocatalytic platforms for CO2 electroreduction, it is essential to have a fundamental understanding of the binding configurations of surface-adsorbed intermediates and the adsorbate-adsorbate interaction within the local environment. In this regard, we discussed recent developments in machine learning-based models of adsorbate-adsorbate interactions for multiple electrochemical reactions (Chapter 5).
- Doctoral Dissertations