Preparation of nanostructured metal oxides for green energy applications via cathodic corrosion

Lawrence, Matthew John ORCID: 0000-0001-5021-665X (2021). Preparation of nanostructured metal oxides for green energy applications via cathodic corrosion. University of Birmingham. Ph.D.

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Abstract

An increase in global population and advances in the development and implementation of technology during the 20th and 21st centuries has resulted in many societies across the globe being heavily reliant on technology for industrial, professional, social and personal use, particularly in developed and developing countries, causing an ever-increasing demand for sustainable and reliable energy. Traditionally, much of the energy produced across the world is sourced from carbon-based fuels, coal, oil and natural gas, which induce detrimental environmental consequences such as the increase in anthropogenic carbon dioxide (CO2) upon consumption, which is associated with the observed global warming. There is social and political pressure to counteract current trends in energy production and CO2 emissions, requiring the large-scale realisation of green energy technologies. However, the intermittent nature of solar, wind and wave power is not suitable to provide reliable energy on-demand. Thus, storing the electrical energy generated by green energy in chemical bonds is advantageous.
Hydrogen production via water splitting is a promising approach for energy storage due to the large natural abundance of water. However, this technology is not fully developed due to the limitations of existing materials to effectively catalyse the oxygen evolution reaction (OER). Electrochemically, the most active catalysts (IrO2 and RuO2) are not earth-abundant and therefore have high associated costs. Photoelectrochemically, the intrinsic properties of binary oxides are not suitable to take advantage of the majority of the solar spectrum. One of the routes towards the optimisation of metal oxide (photo)catalysts for the OER and involves doping the metal oxide semiconductor resulting in changes of the width and position of the semiconductor band gap, in addition to improvement in conductivity and long-term stability. However, the synthetic routes employed for the synthesis of active metal oxide photocatalysts are inefficient, often involving high temperatures and pressures over long timescales.
The electrochemical conversion of CO2 (CO2RR) to useful, value-added chemicals is the subject of significant research effort because this avenue affords an opportunity to take advantage of electrical energy generated by renewable sources such as wind, water and solar. The specific chemical and physical properties of the CO2 reduction reaction (CO2RR) catalyst plays a significant role in the catalytic process. Cu catalysts alone are capable of reducing CO2 to multi-carbon products. Elemental composition, surface geometry, oxidation state, particle size and morphology impact the selectivity and efficiency of CO2RR.
Herein the production of mixed metal oxide nanostructures via cathodic corrosion is presented for the first time. Cathodic corrosion is a single-pot electrochemical etching technique performed at ambient temperatures and pressures, atomising bulk metals into nanoparticles..
The as-prepared oxides were extensively characterised by physical, optical and electrochemical methods, revealing the homogeneity in particle size and elemental composition for binary and mixed metal oxide nanostructures. The optical absorption properties of titanate nanowires was tuned by doping with 3 wt.% Cu2+, leading to enhanced PEC activity. In situ XAS of Cu-titanates during CO2RR revealed that chemical confinement is an effective route to stabilise oxidised Cu species, which have been reported to enhance the selectivity of oxide-derived Cu species towards C2+ products.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):