Year

2021

Degree Name

Doctor of Philosophy

Department

Institute for Superconducting and Electronic Materials

Abstract

Defect engineering is considered as an effective idea for regulating the electronic structure and surface geometric structure of both metal- and carbon-based electrocatalysts. Furthermore, those defects can also be regarded as efficient active sites or collaborate with the surrounding environment to offer unique physical/chemical properties and interactions between active centers and host/support materials. In this regard, a serial of practical defect engineering methods has been developed for the preparation of electrocatalysts for various electrocatalytic processes, including nitrogen reduction reaction (NRR), hydrogen reduction reaction (HER), oxygen reduction reaction (OER), and oxygen reduction reaction (ORR). Comparing with state-of-the-art noble metal catalysts, our fabricated catalysts are much lower in costs but in higher electrocatalytic performances.

Firstly, we adopted a Fe doping strategy to modify the surface atomic structure of W18O49 for effective NRR electrocatalysis and suppressing the HER side reaction. As is known, electrochemical NRR is a promising energy-efficient and low-emission alternative to the traditional Haber-Bosch method for ammonia synthesis. Usually, the competing HER and reaction barrier of ambient electrochemical NRR are the most significant challenges, making the simultaneous achievement of a high NH3 yielding rate and a high Faradic efficiency (FE) extremely difficult for NRR. To address this issue, W18O49, with exposed W sites and intrinsically weak binding for H2, is selected as the substrate and doped by Fe atoms to modify its surface atomic structure for effective NRR electrocatalysis and suppressed HER. On it, a high NH3 yielding rate of 24.7 μg h−1 mgc−a1t. and a high FE of 20.0% have been simultaneously gained at a very low overpotential of −0.15 V vs. reversible hydrogen electrode. Ab initio reveals an intercalation-type doping of Fe atoms in the tunnels of the W18O49 crystal structure, which increases the oxygen vacancies for exposing more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR.

FoR codes (2008)

030306 Synthesis of Materials, 030601 Catalysis and Mechanisms of Reactions, 030604 Electrochemistry

This thesis is unavailable until Wednesday, December 06, 2023

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.