Understanding Electrochemical Interfaces in Energy Storage and Conversion Devices Utilizing First Principles Based Approaches

Siddharth Deshpande, Purdue University

Abstract

Mitigating global climate change and pollution caused by various anthropogenic activities and excess use of fossil fuels is one of the greatest challenges of the 21st century. Electro-chemical devices, as a result of their coupling to renewable sources and portable nature, are at the heart of solving numerous of these challenges. One of the biggest challenges in successful utilization of electro-chemical devices is identifying optimal materials, which will increase the overall economic and energy efficiency of these devices to ultimately replace traditional modes of energy storage and conversion. Electro-catalytic devices form an important subset of electro-chemical devices, making use of a catalytic material to drive the underlying electro-chemical processes, and include devices such as fuel cells, electrolyzers and metal-air batteries. However, compared to their thermal counterparts, these devices are still in their nascency and have been commercialized for only chemical feedstocks containing small molecules such as Cl2, H2, O2 and H2O. One of the major bottlenecks for this discrepancy is the complex nature of the electrified interface, present at the catalyst – electrolyte boundary, which makes it difficult to identify optimal catalytic candidates for such devices. Therefore, to overcome these challenges, there is a pressing need to fundamentally understand the governing interactions and this work is dedicated to utilizing firstprinciples based atomistic simulations to understand the underlying chemistry of such interfaces. First principles-based methods have been key in understanding the underlying atomistic interactions and reaction mechanism for a range of heterogeneous catalytic reactions. Though successful, the utilization of these methods to understand electrified interfaces incorporating complex feedstock, such as ethanol, nitrate, biofuels, amongst others, has been limited. Such studies have been bottlenecked by complexities arising at these interfaces, including solvent effects, co-adsorption effects, solvent dissociation effects and charge transfer from the double layer, amongst others. From first-principles simulation standpoint, these underlying challenges can be broadly divided into two categories: (i) resulting from large phase space of possible atomic configurations, (ii) resulting from the complexities associated with accurately describing the underlying chemo-physical phenomenon at such interfaces. This work aims to address these challenges by development of various algorithmic frameworks and workflows. A graph-theory based in-house algorithm is introduced to tackle problems related to the first challenge and sophisticated workflows utilizing Ab-initio based molecular dynamics, datamining, and charge transfer barrier estimation schemes are utilized to mitigate the latter problems. These algorithms and workflows are then utilized to understand complex electrocatalytic reactions including NO, CH3CH2OH and O2reactants for Pt and its alloys as catalysts.

Degree

Ph.D.

Advisors

Greeley, Purdue University.

Subject Area

Climate Change|Alternative Energy|Chemical engineering|Energy|Materials science

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