Advanced Centre for Energy and Sustainability (ACES)

My research focuses on two interrelated themes - the design of heterogeneous (i.e., solid) catalysts and the development and application of porous materials (i.e., zeolites, activated carbons etc) for gas separation and/or use as a catalyst. The majority of the catalysts we develop target selective hydrogenation. In other words, a catalyst that can control product formation when more than hydrogenated product can form. This is of importance for petrochemical production, fine chemical synthesis and upgrading of biomass. In terms of gas separation, we are interested in the synthesis of materials which are of relevance for carbon capture. Most of my research is conducted in collaboration with colleagues in our School of Engineering (namely, Dr Ines Graca, Dr Panos Kechagiopoulos & Dr Claudia Fernandez Martin).

Recent publications:

S.Biti, A. J. McCue, D. Dionisi, I. Graca, C. F. Martin, Greener carbon capture using microwave heating for the development of cellulose-based adsorbents , Fuel, 2024, 358, 130246,

Summary - this paper targets the production of activated carbons from a cellulose source for use in carbon capture. Cellulose is derived from biomass and so this can be considered as a renewable feedstock (i.e., it can be grown). The activated carbons were synthesised by using microwave heating as opposed to a conventional furnace. This mode of heating is typically far more energy efficient and this therefore reduces the environmental impact of synthesising the activated carbon. The materials synthesised using this approach were shown to be promising for cyclic carbon capture.

Z. Rahmawati, J. A. Anderson, A. J McCue, Selective hydrogenation of stearic acid to stearyl alcohol over cobalt alumina catalysts , Applied Catalysis A: General, 2023, 666, 119437,

Summary - our paper explored the use of cobalt-based catalysts for selectively hydrogenating a long chain fatty acid to the corresponding long chain fatty alcohol. This type of chemistry is important for upgrading naturally occurring oils into more valve added chemicals. This type of chemistry is well known but often relies upon the use of more expensive precious metals like platinum. In our case, we developed an effective catalyst formulation based on cobalt and this therefore reduces the catalyst cost.

B. Fu, A. J. McCue, Y. Liu, S. Weng, Y. Song, Y. He, J. Feng, D. Li, Highly Selective and Stable Isolated Non-Noble Metal Atom Catalysts for Selective Hydrogenation of Acetylene , ACS Catalysis, 2022, 12, 607-615

Summary - this paper explored a new approach to synthesising 'site isolated' Ni based catalysts for selective hydrogenation. Individual Ni atoms were bonded to Mo₃S₄ clusters and then deposited onto a Al₂O₃ support to create a conventional heterogeneous catalyst. In this material, the Ni atoms are isolated/separated from each other and so can act as individual catalytic sites. When compared with a more traditional Ni catalyst (i.e., Ni nanoparticles supported in Al₂O₃) our 'site isolated' catalyst was far more selective for acetylene hydrogenation.

Solid oxide fuel cells (SOFCs) are electrochemical devices that are able to generate electricity from a range of fuels with high efficiency and low emissions of pollutants. However, oxide ion transport in most commercially available solid electrolytes is enabled only at high working temperatures (> 700 °C), thus making the commercialization of SOFCs particularly challenging. The high operating temperature reduces the components' durability, results in slow start up times and the necessitation of expensive materials for seals and interconnects. In order to overcome these issues, it is desirable to develop novel electrolyte materials with significant oxide ion conductivity at intermediate temperatures (300 - 600 °C). We are investigating novel hexagonal perovskites which exhibit both high oxide ion and proton conductivity. We are synthesising a range of hexagonal perovskites with different crystal structure to determine structure property relationships. This will enable us to establish the design rules for obtaining high oxide ion and/or proton conductivity in hexagonal perovskites at intermediate temperature for next generation ceramic fuel cells.

Recent Publications

1. S. Fop, K. S. McCombie, E. J. Wildman, J. M. S. Skakle, J. T. S. Irvine, P. A. Connor, C. Savaniu, C. Ritter and A. C. Mclaughlin, High oxide ion and proton conductivity in a disordered hexagonal perovskite, Nature Materials 19, 752 (2020).

In this paper we show for the first time that it's possible for high dual ion (oxide ion and proton) conductivity to be observed in hexagonal perovskites. The proton conductivity of Ba7Nb4MoO20 is similar to state-of-the-art perovskite proton conductors but the phase is stable under CO2 and does not require extremely high temperatures for synthesis and processing.

2. S. Fop, K. S. McCombie, R. I. Smith and A. C. Mclaughlin, Enhanced Oxygen Ion Conductivity and Mechanistic Understanding in Ba3Nb1-xVxMoO8.5 Chem. Mater. 32 4724 (2020).

3. S. Fop, J. A. Dawson, D. Fortes, C. Ritter and A. C. Mclaughlin, Hydration and Ionic Conduction Mechanisms of Hexagonal Perovskite Derivatives. Chem. Mater. 33, 4651 (2021).

4. S. Fop, J. A. Dawson, D. N. Tawse, M. G. Skellern, J. M. S. Skakle, and A. C. Mclaughlin, Proton and Oxide Ion Conductivity in Palmierite Oxides, Chem. Mater. 34, 8190 (2022).

5. B. Sherwood, E. J. Wildman, R. I. Smith and A. C. Mclaughlin, Enhanced Oxide Ion Conductivity by Ta Doping of Ba3Nb1-xTaxMoO8.5, Inorg. Chem. 62, 1628 (2023).

Hydrogen is a key future energy vector which will be critical to transition away from fossil fuels towards a sustainable energy future. Hydrogen technologies such as fuel cells can use hydrogen as a fuel to produce electrical energy with zero harmful emissions. Research in our group is focussed on the development of innovative solid-state materials for hydrogen-based technologies. Fast hydrogen transport at the atomic level is a fundamental prerequisite for the operation of these technologies. We work on the discovery and design of new hydrogen ion conducting materials with high conductivity at reduced temperatures. These materials will help enabling the widespread use of hydrogen as a zero-carbon fuel for energy generation, as well as for application in important catalytic processes.

Selected Publications:

Anhydrous Superprotonic Conductivity in the Zirconium Acid Triphosphate ZrH₅(PO₄)₃

In the Ab-Elektro Group we focus on the combination of classical electrochemical techniques with in-situ non-electrochemical methods (spectroscopy, microscopy, mass spectrometry), in order to obtain as detailed a description as possible of the electrode-electrolyte interface and of electrochemical reactions at the atomic and molecular level. We try then to apply this knowledge to the development of electrochemical processes and devices with applications in real life, especially within the frame of the energy transition.

Recent publications

• N. Mohandas, T.N. Narayanan, A. Cuesta, Tailoring the Interfacial Water Structure by Electrolyte Engineering for Selective Electrocatalytic Reduction of Carbon Dioxide , ACS Cataysis 2023, 13, 8384-8393,

We show the enhancement of the Faradaic efficiency (FE) of CO₂ reduction to CO on unmodified polycrystalline gold from ∼67 to ∼94% by the addition of up to 15 mol % of N,N-dimethylformamide (DMF) to an aqueous electrolyte. We observed using ATR-SEIRAS changes in the structure of interfacial water induced by the addition of DMF consistent with an increase in the strongly hydrogen-bonded DMF-water pairs with increasingly negative potential near the interface in the presence of DMF. We hold this interfacial water structure modification by DMF responsible for increasing the CO₂RR FE and decreasing the competing hydrogen evolution reaction (HER). Furthermore, the suppression of the HER is observed in other electrolytes and also when platinum was used as an electrode and hence can be a potential method for increasing the product selectivity of complex electrocatalytic reactions.

• X.H. Yang, M. Papasizza, A. Cuesta, J. Cheng, Water-In-Salt Environment Reduces the Overpotential for Reduction of CO₂ to CO₂^- in Ionic Liquid/Water Mixtures , ACS Catalysis 2022, 12, 6770-6780,

We combined computation and experiment to estimate the equilibrium potential for the electroreduction of CO₂ to CO₂^- , providing an alternative view on the reason behind the lower overpotential for CO₂ reduction in imidazolium-based ionic liquid/water mixtures. Ab-initio molecular dynamics delivered no evidence of interaction between EMIM⁺ and CO₂^-. We calculated the equilibrium potential of the CO₂/CO₂^- couple in the mixture and aligned it with the aqueous SHE, proving that the equilibrium potential of CO₂/CO₂^- in the mixture is about 0.3 V less negative than in the aqueous medium. Comparison of computed vibrational spectra with experimental Fourier transform infrared spectra revealed the presence of two water populations in the mixture: (i) bulk-like water and (ii) water in the vicinity of EMIM-BF₄. We showed that stabilization of CO₂^- by water molecules in the EMIM-BF₄/water mixture is stronger than in the aqueous medium, suggesting that water in EMIM-BF₄/water mixtures is responsible for the low overpotential reported in these kinds of electrolytes.

• L. Perez-Martinez, L.M. Machado de los Toyos, J.J.T. Shibuya, A. Cuesta, Methanol dehydrogenation on Pt electrodes: Active sites and role of adsorbed spectators revealed through time-resolved ATR-SEIRAS , ACS Catalysis 2021, 11, 13483-13495,

The dynamics of methanol dehydrogenation to adsorbed CO (CO_ad) on polycrystalline Pt was studied using time-resolved ATR-SEIRAS. Electrooxidation of methanol to CO_ad is possible at potentials at least as negative as 0.01 V vs. RHE and occurs nearly exclusively at (111)- and (100)-oriented defect sites, whereby (111)-oriented defects show higher activity unless blocked by spectator species. Terraces are progressively populated by CO_ad diffusing from the defect sites where it has been formed. We determined the singleton frequency of linearly bonded CO_ad (CO_L) on Pt (2002 cm^-1 ı 2) and detected a band at 1677 cm^-1, which we attribute to adsorbed formyl (HCO_ad) and suggest is the last intermediate in the oxidation to CO_ad. Our experiments also allow the direct spectroscopic determination of Tafel plots revealing the potential dependence of the reaction rate. These plots provide evidence of the important role played by adsorbed spectators in determining the reaction rate.

Dr. Sunita Dey's research focuses on developing novel solid-state materials for battery electrodes and electrolytes, with an emphasis on understanding structure-property relationships during battery operation. Her work particularly targets sustainable synthesis of materials for next-generation, beyond-lithium-ion batteries, and involves studying structural changes in real time using advanced high-energy X-ray facilities.

Prior to joining Aberdeen, Dr. Dey was a postdoctoral researcher and India-DST visiting fellow at the University of Cambridge, working with Prof. Clare Gray on a range of battery materials, employing operando X-ray methods and solid-state NMR techniques. She earned her PhD at JNCASR, India, under the supervision of Prof. C.N.R. Rao, where her research focused on the development of solid-state materials and methods for solar thermochemical water splitting to produce hydrogen.

Ieuan is a Lecturer in the Chemistry Department at the University of Aberdeen and holds a UKRI Future Leaders Fellowship. His research focuses on developing combined experimental and computational tools for the discovery and characterisation of sustainable next-generation materials for energy applications, including rechargeable batteries and fuel cells. A key focus of his work is the development computational methods to understand the long timescale atomistic dynamics in the bulk and at the interfaces of energy materials, using techniques such as transition state searching and Monte Carlo methods. His group also focuses on the development of novel cathode and solid-state electrolyte chemistries for Li and beyond Li-ion batteries with improved sustainability from materials synthesis to end of life.

Before starting at the University of Aberdeen, Ieuan was a postdoc at the Imperial College London (2020-2023) and the University of Texas at Austin (2018-2020), working with Professor Stephen Skinner, Dr Ainara Aguadero and Professor Graeme Henkelman. He investigated the interfacial properties of all-solid-state batteries and the local structure and dynamics of novel cathode materials for Li and Na-ion batteries. This work followed on from his PhD at the University of Cambridge, where he used solid-state nuclear magnetic resonance (NMR) and first principles calculations to understand the local structure of Li-ion battery cathode materials in the group of Professor Dame Clare Grey.

Recent Highlight:

Synergistic Degradation Mechanism in Single Crystal Ni-Rich NMC/Graphite Cells

In this paper, the oxygen loss mechanisms from Ni-rich, LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode materials was studied using a suite of complimentary characterisation techniques, as part of the Faraday Institution Degradation project. It was shown that both the upper and the lower cut off voltage used for cycling full NMC/graphite cells had an important impact on the long-term electrochemical performance. Using density functional theory (DFT) computational models, the thermodynamic origin of surface structural transformations in Ni-rich cathodes was explored, providing a mechanistic understanding of the driving force for Li insertion at different voltages.

Dr. Gibson's work focuses on the development of new layered materials, with a targeted focus on materials with applications in sustainable energy including photovoltaics, thermoelectrics and ionic conductors. Layered materials are one of the backbone's of modern functional materials - finding new way of generating and combining layers represents an attractive method for building the next generation of functional materials. Dr. Gibson's work focuses on combining computational and experimental techniques to predict and synthesize new layered materials and assess their capability for energy applications. A recent research highlight is the discovery of record-low thermal conductivity in a multilayered material with possible applications in thermoelectric materials (Low thermal conductivity in a modular inorganic material with bonding anisotropy and mismatch ).

A theoretical plasma physicist with a decade of numerical, experimental, and industrial research experience, Scott's publication record spans the study of fundamental low-temperature plasma physics to advanced magnetic confinement techniques. His research has found direct and indirect application in areas ranging: aerospace and defense, plasma materials manufacture, plasma-driven solution electrolysis, and nuclear fusion.