Cohort 4 Research Projects

Bethany Willis  Manufacturing of sustainable solar cells
Supervisor: Prof Neil Beattie

This PhD project investigates the various fabrication and manufacturing techniques used for the production of thin film, second generation photovoltaics (PV) like CdTe (Cadmium telluride) CIGS (Copper indium gallium sulphide) or CZTS (Copper zinc tin sulphide).

The sustainability of each process will be evaluated using a Life Cycle Assessment (LCA) software called SimaPro which will provide data based on the environmental impact of different processes. These environmental impacts can range from human toxicity to global warming potential, ozone layer depletion, acidification, eutrophication, abiotic depletion and more. This allows for comparison between different techniques and materials used.

There are different types of LCA, some are Cradle-to-Gate where the life cycle considered is all stages up to the end of manufacturing (mining, transport, manufacturing), Cradle-to-Grave which also includes the use and disposal of the product, Cradle-to-Cradle which also included the potential impacts of recycling the different parts of the product. It is more uncommon for Cradle-to-Cradle LCA for PV systems due to the insufficient reliable data. Many assumptions also need to be made when conducting an LCA, for example the life-time of the solar panel, the way that materials are transported from their extraction to the manufacturing stage, the percentage of product that is recyclable and more. A sensitivity analysis will be used to compare different methods used to carry out the LCA and validate the accuracy of the results.

To improve the LCA, experiments will be carried out alongside the LCA investigations where the fabrication of a sustainable solar cell can be completed and real data can be collected for use within the SimaPro software. This means a fully functional solar cell can be produced and it allows for the evaluation of the quality of this solar cell that has been created with sustainability as the central focus.

The outcomes of this research have the potential to be applied to other researchers work to show that techniques that they are using can be considered as sustainable. For example, for research which involves the fabrication of solar cells using inkjet printing or the same nanoparticle ink the authors can include parts of this research which describe the environmental impacts of using such materials and processes. With the rapidly increasing capacity and demand for solar power and rapidly decreasing availability for raw resources, sustainability is quickly becoming an important factor in all aspects of research.

The main aim of this project it to use LCA to find, currently, the most sustainable method of producing a functioning thin-film solar cell. This links closely to one of the priorities expressed by the UKRI of engineering net zero and the idea that the findings of this project can be used for a step towards green energy production.

Beyond the single solar cell, work can advance onto looking at the sustainability when these solar cells are integrated into products and buildings and how effective this idea is for the future of PV.

This project is supported by a number of universities and partners in the North East of England as part of the RENU doctorial training programme, primarily Northumbria University, Newcastle University and Durham University as well as collaborations with the Royal Society of Chemistry and the Institute of Physics.

David Roughton-Reay  Bio-inspired electrodes for energy transport applications in renewable energy devices
Supervisor: Dr Prashant Agrawal

The aim of my project is to produce bio-inspired structures which function as electrical contacts. Integration of multiscale feature structures as contacts will ideally follow the same characteristics as leaf-venation patterns; providing optimal coverage for electron transport while producing as little optical shading as possible. This project will investigate the potential for feature scalability, repeatability and overall shape flexibility. The goal application for these bio-inspired structures is as solar cell top contacts, meaning that the fabricated contacts will be compared to existing solar cell top contacts for conductivity and optical transparency

Markus Hußner  – Mathematical model of solar cells
Supervisor: Prof Roderik MacKenzie and Prof Chris Groves

The aim of my project is to produce bio-inspired structures which function as electrical contacts. Integration of multiscale feature structures as contacts will ideally follow the same characteristics as leaf-venation patterns; providing optimal coverage for electron transport while producing as little optical shading as possible. This project will investigate the potential for feature scalability, repeatability and overall shape flexibility. The goal application for these bio-inspired structures is as solar cell top contacts, meaning that the fabricated contacts will be compared to existing solar cell top contacts for conductivity and optical transparency

Tesfay Berhe Gebreegziabher  – Biomass-based Carbon for Hydrogen Storage
Supervisor: Dr. Yolanda Sanchez Vicente, Dr. Dominika Zabiegaj, and Dr. Roni Pini

Introduction

Nowadays, due to the worsening climate change and energy crisis, the need for alternative energy sources is vital. Hydrogen has emerged as one of the green energy carriers. However, its shipment and storage have been the challenges. Experts have managed to store hydrogen in underground cavities, pressure tanks, and liquid hydrogen. However, these storage systems suffer from several setbacks such as limited storage capacity, low energy efficiency, high cost, and safety concerns.

To overcome the above setbacks, reliable, safe, and efficient alternative technologies, which provide large gravimetric capacity at ambient conditions are crucial. Hence, due to the rapid release of hydrogen on demand, natural abundance of raw material, and the good track record of regeneration, hydrogen storage in porous carbons is regarded as a promising technology. Despite the emergence of promising reports of hydrogen storage capacities in carbon material, no material is yet to meet the market standards set by the US Department of Energy. To date, unprecedented efforts have been made to maximize the hydrogen adsorption potential of porous carbons at ambient conditions. Among these methods, hydrogen spillover and heteroatom doping are believed to improve the hydrogen storage potential of carbon-based materials at ambient conditions. Reports show that metal-doped porous carbon revealed a significant improvement in hydrogen uptake capacity due to the hydrogen spillover effect. This project will deeply analyse the synergistic effect of wmetal decoration and heteroatom doping on the hydrogen storage potential of different biomass-based carbons like spent coffee, nut shell, and corncob.

The major objectives will be to:

  1. Synthesize different biomass-derived activated carbons for hydrogen storage.
  2. Enhance the hydrogen uptake capacity of the porous carbon by doping with transition metals and heteroatoms.
  3. Characterise and analyze the properties of the porous carbon for its morphology, porosity, textural properties, thermal stability, and reusability.
  4. Develop mathematical models of the adsorption isotherm, kinetic, and thermodynamic properties of biomass-derived carbon.

Porous carbon synthesis procedure and hydrogen adsorption

First, a biomass precursor will be washed with distilled water and dried at hot air oven. Then, the dried biomass precursor will be pyrolyzedin a horizontal electric furnace and heated to 400 and 450 °C in a stream of argon gas. Then, the carbonized samples will be impregnated into a potassium hydroxide and transferred to a horizontal electric furnace, and activated at a temperature of 800 and 850 °C. Finally, the activated carbon samples will be washed with distilled water and dried. The prepared porous carbon will then be doped with different transition metals (Ni, Pt, Ni) and heteroatoms (N2, B, O2).

Hydrogen adsorption experiments and characterization of porous carbon

To evaluate the hydrogen adsorption potential of the porous carbon the manometric/Sievert’s method will be used. Then, the spent activated carbon will be reused repeatedly in several cycles to test the reuse of the porous carbon.  The synthesized porous carbons will be characterized using different characterization techniques such as proximate and elemental analysis, surface morphology, textural properties, energy-dispersive x-ray spectroscopy, Fourier transform spectroscopy, thermogravimetric and differential thermal analysis.

This project is believed to have a substantial contribution to the development of novel carbon hydrogen storage materials for ambient operating condition applications toward achieving a hydrogen-based economy.

Mian Muhammad Faisal  Novel Flexible Materials for Sustainable Energy Storage
Supervisor: Prof Roderik MacKenzie and Prof Chris Groves

The continued growth in world energy demand coupled with the increasingly pressing need to address climate change is rapidly driving a transition to renewable and sustainable energy sources. Renewable energy generation can often be intermittent and does not always align well with fluctuations in demand (for example, solar electricity generation can only occur during daylight, whereas peak energy demand may be in the evening) and there is a need for portable energy storage in applications as diverse as vehicles and personal electronics. Existing battery technologies have a limited lifetime, are difficult to recycle, and are produced from raw materials often mined unsustainably and with issues over the geopolitical location. Hence, there is a profound need for developing electrical energy storage with a long cycle life produced from sustainable materials by environmentally acceptable processes. The focus of this research project is to develop a highly performance-promising class of energy storage devices, known as supercapacitors for ‘green’ energy storage. Successful development of such devices can have a major impact on the rapid adoption of renewable energy and sustainable transport, ameliorating anthropogenic global climate change.

Like batteries, supercapacitors are devices that store energy electrochemically. However, unlike the former, electrical charge is stored at the surface of the materials making up the electrodes within the device, rather than in the bulk. This has the twin advantages of allowing rapid charging/discharging and substantially reducing the rate at which their storage capacity degrades. However, they have a significant disadvantage in the amount of electrical energy which can be stored. Moreover, neither traditional battery nor supercapacitor materials have mechanical properties which enable them to be readily incorporated into durable wearable and flexible devices.

To address these issues this project aims to develop novel materials and structures, particularly electrodes, which will enable the production of flexible supercapacitors with improved charge storage capacity produced from Earth-abundant and sustainably obtained materials through processes with limited environmental impact. Free-standing flexible composite electrodes will be created using a ‘backbone’ of carbon cloth onto which will be grown novel ‘pseudocapacitive’ materials. These materials will be chosen on the basis of an evaluation of their likelihood to combine high charge storage capacity (due to similarities with battery chemistry) with high cycle life and power output. Wet chemical techniques and hydrothermal growth will initially be to fabricate such electrodes and routes to sustainable production will be developed. Thorough characterization of their physical structure and chemical composition will be undertaken to understand appropriate structure-function relationships and optimize both materials and processing. The resulting electrodes will be assembled into flexible energy storage devices which will be evaluated for their electrochemical performance.

Jemma Cox  The Development of Recyclable Hybrid Solid Electrolytes for Battery Applications 
Supervisor: Dr Karen Johnston, Dr Clare Mahon and Dr James Dawson

The exponential growth in rechargeable battery technologies over the last 20 years is due to the rising demand for portable electronics, but more recently, batteries have become an increasingly important means of storing energy, to drive the use of renewable energy resources and decrease the impact of human activity on the environment.  

Since their development in the 1970s-80s, lithium ion (Li-ion) batteries have dominated the field, exhibited by the award of the Nobel Prize in Chemistry in 2019 to Goodenough, Whittingham and Yoshino. Li-ion batteries have enabled the development of electric vehicles and the storage of energy from renewable sources, such as solar and wind power. Their significant downfall, however, is the use of lithium salts in organic solvents as the cell’s electrolyte, which are highly flammable and pose potential safety risks, such as fires and explosions. An explored alternative to these dangerous solvents are solid or semi-crystalline electrolytes (SEs), which have shown to improve the safety of Li-ion batteries, producing what is known as an all-solid-state battery (ASSB). 

This PhD research encompasses the development of recyclable hybrid solid electrolytes for implementation into solid-state battery systems, with the hybrid element being a polymer/ceramic combination. Some polymers are capable of functioning effectively as electrolytes, and display the robust mechanical properties required for use in everyday devices, i.e., poly(ethylene oxide)s (PEO) displays considerable flexibility and chemical stability, making them excellent candidate materials for SEs. Yet, their commercialisation alone isn’t feasible due to their inability to meet the practical conductivities required (~10−3 S cm−1) due to the frustrated transport of ions through the material. Therefore, polymer electrolytes can be combined with ceramic fillers such as Al2O3 or TiO2, drastically improving the ionic conductivity of the SEs, without affecting their mechanical strength. 

The project explores the potential of such poly(acetals) in hybrid electrolytes, assessing their ion transport mechanisms using a combination of conventional and in situ solid-state NMR spectroscopy, in conjunction with impedance measurements and muon spin relaxation spectroscopy studies. The effects of structural parameters of the polymers such as monomer composition and degree of polymerisation on the resultant mechanical properties will be assessed, to enable the production of robust electrolytes. A range of different inorganic ceramics will also be evaluated to determine the optimal poly(acetal):ceramic combination. Key research in this area will be to evaluate the performance of the hybrid electrolytes prepared relative to current PEO-based electrolytes, to determine their standing within the community of solid electrolytes. Additionally, computational techniques, including atomistic modelling and DFT calculations will be utilised to understand the ion mobility within the new SE materials. 

This project spans multiple EPSRC research areas including materials for energy applications, energy storage, polymer materials, materials engineering (ceramics), computational chemistry, and functional ceramics and inorganics, with the work falling under the themes of energy and manufacturing the future, as well as circular economy.  

James Ramsey  Atomically Thin Photovoltaics
Supervisor: Dr Aleksey Kozikov

Atomically Thin Solar Cells: 

Sustainability is a predominant idea in the energy sector to protect the planet going forward, with many countries including the U.K. setting “net-zero” carbon emission targets by 2050. Renewables are methods of energy generation which do not directly emit carbon-based greenhouse gases, these include: wind, hydropower, and solar power. 

The sun’s energy can be harvested at no direct cost to the planet using a solar panel. This is a device which converts the energy from the sun’s light to electricity. Solar cells, alternatively called photovoltaic (PV) cells are the units which make up solar panels. The efficiency of a PV cell quantifies how effective it converts energy from the light to electricity – current commercial solar panels based on silicon (Si) achieve ~25% efficiency, which is the industry’s standard. 

Alternative materials to Si are explored so that they can be used where silicon’s properties may restrict the applications of devices based upon them. For example, traditional PV cells suffer decreasing efficiency as they become thinner, typically not reduced below 0.1-0.4mm. These are made from Si and metals, rendering them heavy, non-flexible, and visible to the eye, restricting their applications. The alternative materials investigated in this project may be scaled down to just a few atoms in thickness (hence are called atomically thin), rendering them light, flexible, invisible to the eye and ~100,000 times thinner than Si devices. Imagine placing PV in new places like clothing, your phone, or coating buildings. Unfortunately, the best achieved efficiencies from atomically thin PV cells are comparably worse than Si at ~5-10%, but this may not be the ultimate factor for viability if they can be placed in new locations. 

PV cells only function under solar illumination which is not always available due to time of day or weather on Earth, therefore, they have always been explored for extra-terrestrial use to circumvent this. An important consideration for space applications is spacecraft launch costs, mainly depending on mass and volume. Atomically thin materials have several main advantages here due to their low mass and volume. They have been proven to withstand the harsh radiation found in space, and their flexibility would allow electricity generation on the body of the spacecraft. This could supplement the craft’s existing solar panels, without increasing its volume. This may lead to high suitability for use in space.  

Aims: 

This project aims to increase the efficiency of atomically thin PV cells through the novel application of highly reflective mirrors to increase photon absorption, optimum material choices, and sizing of the cells. The feasibility of these devices for concentrator solar cells will be investigated which will bring another element of novelty. Concentrator cells are those where the intensity of light is increased by focusing it upon the cell to achieve higher efficiency. This increased intensity may damage the cells, akin to fire starting due to light through a magnifying glass, therefore it must be shown that they are undamaged for to demonstrate their suitability. 

Methodology: 

The PV cells will be produced by cleaving apart the layers of materials known as transition metal dichalcogenides, and black phosphorus. This can be done until they are only one atomic layer thick because these materials’ layers are only bonded weakly. Layers of different materials can then be stacked upon one another however you choose, analogous to how one stacks Lego pieces, to produce new materials with specific properties. These devices can then have their thickness characterised by atomic force microscopy, and their chemical composition by Raman spectroscopy. Their efficiency is determined by measuring electrical current generated when the devices are illuminated by a solar light simulator, however a laser can be used to determine the response when specific positions on the device are illuminated. 

Jessica Bedward  – Bioethanol Upgrading Catalysed by Multifunctional Zeolites
Supervisor: Dr Russell Taylor and Dr Karen Johnston

Since 2015, global production of bioethanol from biomass-based feedstocks has exceeded 25 billion gallons per year. The negative environmental impacts derived from the chemical industry’s dependence on fossil fuels means that there is an ever-increasing pressure to utilise renewable alternatives. Consequently, the upgrading of bioethanol into higher value chemicals and fuels is of great interest in both academia and industry.

Bioethanol is predominantly used as a drop-in renewable fuel additive to gasoline. Unfortunately, bioethanol is corrosive to most engines and so only low levels (10%) can be added to gasoline without suitable engine modification. Additionally, bioethanol has a lower energy density (70%) than gasoline and is water miscible, potentially causing problems with separation and dilution in storage tanks. Contrastingly, biobutanol, derived from bioethanol, is a much better renewable additive for gasoline engines; it has 90% the energy density of gasoline, is non-corrosive and has limited miscibility with water so it can be blended at higher concentrations, or even be used as a stand-alone biofuel.

Currently, precious metal based, catalysts are typically utilised for the conversion of ethanol to butanol. These catalysts however are unsustainable for industrial manufacture of biobutanol, and their production and disposal are considered both environmentally and economically problematic. Development of effective catalysts from earth abundant, non-toxic materials would therefore overcome a major barrier in the commercialisation of this process.

Zeolites are microporous aluminosilicate materials used as sustainable catalysts in a range of industrial processes such as catalytic cracking. Their highly stable, cage-like structure allows for shape-selective catalysis, and they can be structurally modified to accommodate numerous different active sites, resulting in an ability to catalyse multistep reaction process.

Recent work in the Taylor group at Durham University has shown that zinc oxide (ZnO) supported on zeolites gives rise to very stable ethanol dehydrogenation catalysts (over 120 hours), which is the first step in the ethanol to butanol reaction cascade. This project aims to modify these ZnO/Zeolite catalysts further, with additional active sites to complete the full ethanol to butanol cascade pathway. This will include earth abundant, extra‑framework metal sites, as well as framework Lewis acid sites. The project will determine how the nature and location of the differing catalytic components affects overall catalytic function, which will provide structure function models for future catalyst design. The location of the different catalytic functionalities will be controlled via a variety of different synthetic approaches. The multistep conversion of ethanol to butanol will be explored using flow reactors coupled with online analysis, and mechanistic pathways will be probed by in-situ infrared spectroscopy.

This project spans multiple EPSRC research areas including bioenergy, catalysis, chemical reaction dynamics and mechanisms, and functional ceramics and inorganics. The research falls under the themes of Energy and Manufacturing the Future, with the primary goal being development of catalysts for biofuel production.