Photo-active Materials

Photo-active Materials

Professor Macphee is currently involved in the following research projects:

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 on an illuminated semiconductor photocatalyst, through the role of the photocatalyst surface on performance, to the influence of cement chemistry on these processes and the role of the catalyst support on catalyst performance.

Our research has received support from various funding agencies. Project Light2CAT, funded under the EU FP7 Framework, 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 joint EPSRC-NSFC funding enabled collaboration with researchers at Wuhan University of Technology aimed at optimising catalyst supports for construction applications. Collaboration with researchers at the Universidade Federal da Paraíba, funded by CAPES, has focussed on the photocatalytic performance of supported perovskite photocatalysts for wastewater applications.

Selected Publications

• “Photocatalytic Concretes - The interface between photocatalysis and cement chemistry”, Macphee, D.E. and Folli, A., Cement and Concrete Research, 85, 48-54, (2016), 10.1016/j.cemconres.2016.03.007 .
• “Different Roles of Water in Photocatalytic DeNOx Mechanisms on TiO₂: Basis for Engineering Nitrate Selectivity?”, Yang, L., Hakki, A., Wang, F. and Macphee, D.E., ACS Appl. Mater. Interfaces, 9, 20, 17034-41, (2017), DOI: 10.1021/acsami.7b01989 .
• “Improving the Selectivity of Photocatalytic NO_x Abatement through Improved O₂ Reduction Pathways Using Ti_0.909W_0.091O₂N_x Semiconductor Nanoparticles: From Characterization to Photocatalytic Performance”, Folli, A., Bloh, J.Z., Armstrong, K., Richards, E., Murphy, D.M., Lu, L., Kiely, C.J., Morgan, D.J., Smith, R.I., Mclaughlin, A.C. and Macphee, D.E., ACS Catalysis, 8, (8), 6927-38, (2018), 10.1021/acscatal.8b00521 .
• “Photocatalytic Concrete for NOx Abatement: Supported TiO₂ efficiencies and impacts”, Yang, Lu, Hakki, A., Zheng, L., Jones, R., Wang, F. and Macphee, D.E., Cement and Concrete Research, 116,57-64, (2019), 10.1016/j.cemconres.2018.11.002 .
• “Supporting the Photocatalysts on Commercial oxide: An Effective Way to Enhance the Photocatalytic Activity of SrSnO₃”, Castro Honorio, L.M., Menezes de Oliveira, A.L., da Silva Filho, E.C., Osajima, J.A., Hakki, A., Macphee, D.E., and Garcia, Dos Santos, I.M., Applied Surface Science, 528, 146991, (2020), 10.1016/j.apsusc.2020.146991 .
• “A combination of epr, microscopy, electrophoresis and theory to elucidate the chemistry of W-and N-doped TiO₂ nanoparticle/water interfaces”, Gorman, S., Rickaby, K., Lu, L., Kiely, C.J., Macphee, D.E. and Folli, A., Catalysts, 11, (11), 1305, (2021), 10.3390/catal11111305 .

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); CO may enter the fuel cell as an impurity in the fuel (i.e. in hydrogen 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 cell's 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 reduced when using tungsten oxide as a co-catalyst under illumination.

The key proposition is to maximise fuel cell performance 'in service', minimise the cost of usable fuel (using low purity reformate hydrogen), and thus provide greater fuel efficiency and longer service life. Together with industry partners, including fuel cell stack and optical component developers and distributors, core 'catalyst illumination' technology has been under development.

Selected Publications

• “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), 10.1016/j.desal.2008.05.048 .
• “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), 10.1007/s10008-010-1062-4 .
• “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), 10.1016/j.apcatb.2012.05.010 .
• “Photocatalytic Reactor”, Macphee, D.E., International Publication Number: WO2004079847 A
• "The Role of Tungsten Oxide in the Enhancement of Carbon Monoxide Tolerance of Platinum-Based Hydrogen Oxidation Catalysis", Stewart, D., Scott, K., Wain, A., Rosser, T., Brightman, E., Macphee, D., Mamlouk, M., ACS Appl. Mater. Interfaces, 12(33), 37079-37091, (2020), 10.1021/acsami.0c07804 .