Professor Donald MacPhee

Research Overview

Cement Chemistry

Portland cement has many uses but it is best known as the binding constituent of concrete, the most extensively used man-made construction material in the modern world. Although considered largely an engineering material, its setting and subsequent durability properties are controlled by chemistry. Consequently, cement chemistry research, over many years, has lead to a range of technologically significant products and processes.

Cement formulations appropriate for extreme environmental conditions are used routinely in mine stabilisation, oil well cementing, underwater construction, cold weather climates, etc. · Durable concretes can be designed to limit degradation that previously would have arisen due to reinforcement corrosion, alkali aggregate reaction and sulphate attack. Of significance today is the environmental impact of Portland cement manufacture and focus is directed towards reducing the resulting CO₂ emissions. More efficient use of Portland cement through the use of supplementary cementitious materials (SCMs) and the development of alternative cements are amongst the key research strategies adopted by industry and academia in addressing this.

Current Research

The Cements Research Group within the Department of Chemistry at the University of Aberdeen have research activity over a broad range of areas. Professor Macphee is currently involved in several areas:

Reactivity of glassy aluminosilicates

Glass reactivity is of interest across a range of technological themes. In geology, the weathering of igneous and metamorphic rock types is through glass reaction with its exposure environment. In waste management, glasses are used as primary matrices for the immobilisation of high level nuclear waste and as reactive constituents in cementitious matrices for low and intermediate level nuclear wastes. In construction, as with cementitious waste forms, Portland cements are commonly extended with glassy aluminosilicates, such as coal combustion fly ash or blastfurnace slags. Understanding the reactivity of these materials therefore has technological importance. Our focus is on the use of aluminosilicate glasses as supplementary cementitious materials (SCMs) and funding from the European industry-academic network, Nanocem, has enabled detailed dissolution rate studies including time resolved solution analysis (MIP-OES) and high resolution surface characterisation (ToF-SIMS and XPS) of model glasses.

• “The early stage dissolution characteristics of aluminosilicate glasses and their implications for SCM reactivity in cement systems”, Newlands, K.C. and Macphee, D.E., Proc. 19 Int. Baustofftagung, (Weimar, 2015), I 77-90.

• “Early Stages of Aluminosilicate Glass Dissolution”, Newlands, K.C. and Macphee, D.E., Oral presentation, Goldschmidt 2014, (Sacramento, CA, 2014).

Photocatalysis and photocatalytic cements

The use of photocatalysts in construction is one of the most sustainable technologies for atmospheric depollution. Globally, concrete structures are ubiquitous in the built environment. Their surfaces are exposed to solar radiation at varying intensities, dependent on latitude, season, time of day, angle of exposure and local weather conditions and they represent significant surface areas which, particularly in urban settings, are typically exposed to the highest levels of air pollution. Our interests range from the fundamental processes activated in an illuminated semiconductor photocatalyst, through the role of the photocatalyst surface on performance, to the influence of cement chemistry on these processes. We have recently completed a European project (Light2CaT) under the European Union’s Seventh Framework Programme (FP7), which led to the development of a visible light TiO₂-based photocatalyst with a high degree of selectivity for nitrate during the photocatalytic oxidation of atmospheric NOx gases, and we are currently partners in an EPSRC-NSFC joint programme with researchers at Wuhan University of Technology and Chongqing University aimed at optimising catalyst supports for construction applications.

• “Engineering Photocatalytic Cements: Understanding TiO₂ Surface Chemistry to Control and Modulate Photocatalytic Performances”, Folli, A., Pochard, I., Nonat, A., Jakobsen, U.H., Shepherd, A.M. and Macphee, D.E., J. Am. Ceram. Soc. 93 (2010) 3360–3369.

• “Adjusting Nitrogen Doping Level in Titanium Dioxide by Codoping with Tungsten: Properties and Band Structure of the Resulting Materials”, Bloh, J.Z., Folli, A., Macphee, D.E.,  , J. Phys. Chem. C. 118 (2014) 21281–21292.

• “Properties and photochemistry of valence-induced-Ti³⁺ enriched (Nb,N)-codoped anatase TiO₂ semiconductors”, Folli, A., Bloh, J.Z., Lecaplain, A., Walker, R. and Macphee, D.E., Phys. Chem. Chem. Phys. (2015).

• “TiO₂ photocatalysis in cementitious systems: Insights into self-cleaning and depollution chemistry”, Folli, A., Pade, C., Hansen, T.B., De Marco, T. and Macphee, D.E., Cem. Concr. Res. 42 (2012) 539–548

He is also involved in research outside of the cement chemistry theme:

Photo-responsive materials for fuel cell and related applications

The commercial uptake of low temperature fuel cells has been limited by the durability of the membrane electrode assembly (MEA). Amongst the most common of the MEA failure modes is the poisoning of the platinum anode electrocatalyst by adsorbed carbon monoxide (CO), entering the fuel cell in the fuel (where hydrogen is derived from the reformation of hydrocarbons, or if in a direct methanol fuel cell (DMFC), from fuel oxidation).  CO adsorption can rapidly degrade anode performance at concentrations of only a few parts per million in the fuel. Fuel purity therefore adds cost to the fuel cells cost of ownership, through fuel and component replacement costs as well as in the fuel cell down time. Our research in this field grew from our studies on tungsten oxide photocatalysis for water purification and a recognition that the expected drop in a DMFC test cell electrode performance was significantly limited under illumination. Development of this theme has led to several patents and the formation of Enocell Ltd, a university spin out company formed in 2011.

• “A visible light driven photoelectrocatalytic fuel cell for clean-up of contaminated water supplies”, Macphee, DE, Wells, RPK, Kruth, A, Todd, M., Elmorsi, T., Smith, C., Pokrajac, D., Strachan, N, Mwinyhija, M, Scott-Emuakpor, E, Nissen, S and Killham, K, Desalination, 248, 132-7, (2009).

• “A Tungsten Oxide-Based Photoelectrocatalyst for Degradation of Environmental Contaminants”, Macphee, DE, Rosenberg, D, Skellern, MG, Wells, RPK, Duffy JA  and Killham K., Journal of Solid State Electrochemistry, 15, (1), 99-103, (2011).

• “Remediation of 2,4-dichlorophenol contaminated water by visible light-enhanced WO3 Photoelectrocatalysis”, Scott-Emuakpor, EO A Kruth, MJ Todd, A Raab, GI Paton and DE Macphee, Applied Catalysis B: Environmental, 123–124, 433– 439, (2012).

• “Photocatalytic Reactor”, Macphee, D.E., International Publication Number: WO2004079847 A)

Teaching Responsibilities

Professor Macphee is Course Co-ordinator for Level-5 Chemistry Courses and teaches in the following courses:

• CM1011 Essentials of Chemistry
• CM3020 Solid State Chemistry
• CM3517 Environmental Chemistry and Chemistry of the Elements
• CM4017/CM4024 Honours/Advanced Chemistry
• CM5003 MChem Chemistry Applications

Professor Macphee's 4th Year Lecture notes (on cement chemistry)