Synthesis and Electrocatalytic Properties of Structure Engineered First-Row Transition Metal Derivatives
Abstract
Hydrogen is a green energy carrier, producing only water when combusted, and a
hydrogen economy has been considered the ideal green economy for human society. Water
electrolysis can produce high-purity hydrogen on a large scale, and if the electricity used in
water electrolysis is obtained from renewable energy, a sustainable energy chain can be
achieved.
Fuel cell technology offers a highly efficient way of converting chemical energy from
a fuel into electricity through an electrochemical reaction. Fuel cells are expected to be one of
the mainstream energy conversion devices for many applications such as the transportation
and portable electronic systems. Hydrogen fuel cell technology is, of course, the ideal choice.
However, the hydrogen storage is still a big challenge due to its gaseous nature, extremely low
boiling point, and high inflammability. While advanced hydrogen storage technology is under
development, fuel cells using liquid fuels (e.g. hydrazine) need to be developed.
The key to both water electrolysis and fuel cells is the electrocatalyst. Currently, the
noble metal based materials are still the state-of-the-art electrocatalysts for water electrolysis
and in fuel cells in terms of catalytic activity and catalyst durability. However, their scarcity
and high price hinder their widespread commercial use. Therefore, it is imperative to develop
earth-abundant, low-cost electrocatalyst materials that have high catalytic activity comparable
to or even better than the noble metal based electrocatalysts. Nowadays, the research emphasis
of earth-abundant electrocatalysts is thus primarily placed on enhancing the catalytic activity
or lowering the overpotential that is needed to drive the electrochemical reactions. The
catalytic performance of an electrocatalyst is associated with its surface area, near-surface
structure, electronic structure, conductivity, crystal size, etc. Rational structural modification
of the electrocatalyst materials and/or architectural design of the catalyst electrodes can help
enlarge the surface area, increase the active sites, tune the electronic structure and conductivity,
and so on. In this dissertation, a series of strategies (e.g. hydrogenation, solvothermal
reduction, and electrochemical tuning) have been developed to fabricate structure-tuned
electrocatalyst materials for electrochemical water splitting and electro-oxidation of hydrazine.
Well-defined Co/Co₃O₄ and Co/CoO core-shell heterostructures have been found to be highly
active towards hydrogen evolution reaction (HER) and hydrazine oxidation, respectively.
FeNi₃/NiFeOₓ nanohybrids have been thoroughly characterized for HER and oxygen evolution
reaction (OER). Nano-on-micro Cu has been explored as a highly efficient catalyst towards
electro-oxidation of hydrazine. Cobalt hydroxide carbonate with rich grain boundaries has
been shown to be a highly efficient non-metallic electrocatalyst towards hydrazine oxidation.
Table of Contents
Introduction -- Structure-engineered first-row transition metal derivatives as electrocatalysts for water electrolysis -- structured-engineered first-row transition metal derivatives as electrocatalysts for hydrazine oxidation -- Summary and conclusions
Degree
Ph.D.