Experimental Characterization and First-Principles Simulation of Materials-Electrolyte-Gas Interfaces in Energy Applications

Abstract

Renewable energy-driven electrocatalytic water splitting is a highly desirable and sustainable process for large-scale green hydrogen production. Hydrogen and oxygen bubbles govern the overall performance of a gas-evolving electrocatalyst/electrode by inducing extra transport resistance. Though micro/nano-structured electrode surface can play an important role in controlling bubble behavior, how to enhance transport via nanoengineered porous electrode remains elusive. By casting porous Ni5P4 nanoparticles (50–500 nm pores) on Ni foam (200–600 µm pores) (p-Ni5P4@NF) along with in-situ macro/microscopic high-speed imaging, this dissertation provides insights into hydrogen and oxygen bubble dynamics during water splitting. Porous Ni5P4 offers abundant cavities for gas nucleation and fast growth of H2 bubbles, and small bubbles (10–50 µm) depart quickly owing to the reduced contact line. With enhanced gas transport and reduced bubble overpotential (over 29%), the proposed pNi5P4@NF electrode achieves excellent electrocatalytic performance. In order to ensure the electrode stability and high-performance electrocatalysis, in-situ grown NiFe hydroxide nanosheets are developed on various porous substrates, and the transport efficiency varies with the substrate geometry due to different bubble growth, departure sizes and coverage patterns. The interfacial interaction and intrinsic electrocatalytic activity at NiFe hydroxide@Ni interface are analyzed by using density functional theory (DFT)-based first-principles simulation. This ab-initio method is also applied to provide atomic insights into ionic liquid (IL)-water interfaces in other energy applications, where strong adhesion is attributed to intermolecular hydrogen bonding and polar interaction because of TFSIstereoselective isomerization.

This dissertation provides instrumental approaches to enhancing energy transport with tailored solid-solid/liquid/gas and liquid-liquid interfaces.

Date of Award	25 Dec 2023
Original language	American English
Supervisor	TJ Zhang (Supervisor)