Research and Outreach
Solar Fuels: It is widely recognised that there is a need to transition to low carbon energy technologies. Abundant renewable energy resources exist; the annual solar energy incident on the earth is 8000 times greater than the entire global energy requirements of humankind in a year. However the intermittent nature of these resources presents a challenge. This is a particularly acute problem for non-equatorial areas where long term (many months) energy storage will be required if we are to transition fully to solar energy. Chemical fuels have high energy densities and the existing infrastructure for the storage and transportation for many months’ worth of energy already exists.
The overarching aim of the group is to explore new routes to generating existing fuels by sustainable ways. In particular we are interested in the chemistry of fuel (e.g. methanol) and fuel precursor (e.g. carbon monoxide, hydrogen) generation from water and carbon dioxide using renewable energy resources. This is a field sometimes called solar fuels, or artificial photosynthesis. Further information on the potential applications of solar fuels can be found in a recent document produced by the RSC.
The group is active both in the development of new catalytic materials and in the application of advanced spectroscopies to study the reaction mechanisms of current state of the art systems. Further details of each topic can be found below.
1. Developing new electrocatalysts for the reduction of CO2 in water:
CO2 can be electrochemically reduced to higher value products such as carbon monoxide, methane and methanol. To make the process sustainable CO2 reduction will need to be coupled to water oxidation. Currently relatively few moleuclar electrocatalysts for CO2 reduction in water are known. Our group is exploring both the development of water soluble electrocatalysts and the construction of hybrid electrode materials where a molecular catalyst is immobilised to a high surface area conductive support.
References: 1. Chem. Sci., 2016,7, 1521-1526, 2. Faraday Discuss. 2015, 183, 147-160,3. Chem. Commun., 2014, 50, 12698-12701
2. CO2 reduction photocatalysts:
The direct light driven reduction of CO2 in water is challenging as proton reduction leading to hydrogen production often dominates. Our approach is to immobilise highly selective electrocatalysts onto and near to visible light absorbers. Photon absorption by the sensitizer generates a high energy photoelectron which can transfer to the catalyst enabling CO2 reduction.
References: 1. Chem. Commun., 2016,52, 14200-14203, 2. Phys. Chem. Chem. Phys., 2016,18, 24825-24829, 3. Phys. Chem. Chem. Phys., 2014, 16, 5922-5926
3. Sum Frequency Generation (SFG) Spectroscopy
IR-Vis SFG spectroscopy is a powerful technique that selectively probes interfacial species. We have been working with the UK central laser facility to develop a IR-Vis SFG experiment for the study of electrochemical interfaces. This experiment is now being applied to the catalytic mechanisms of some of the most widely studied CO2 reduction electrocatalysts under potentiostatic control. The ability of SFG spectroscopy to identify intermediates at sub-monolayer coverages on the electrode surface in real-time during CV scans is providing remarkable levels of mechanistic detail.
4. Transient spectroscopy of photoelectrodes:
Our approach is to try study the fundamental factors controlling the efficiency of photoelectrodes so that the next generation of materials can be developed in a rational manor. We employ a range of techniques including time-resolved spectroscopic and electrochemical measurements alongside material development programmes, carried out in partnership with collaborators. In particular we study photoelectrochemical systems for water splitting and carbon dioxide reduction, an example of which is shown below. Through the use of laser based transient absorption spectroscopy and transient electrochemical methods it is possible to measure the dynamics of photo-electrons and holes in an operational cell. We have particular expertise in the study of hematite, a very promising low cost material that can be used for water oxidation.
References: 1. Nature Chemistry, 2016, 8(8), 740-741, 2. Chemical Science, 2015, 2015, 6, 4009-4016, 3. Angew. Chem. Int. Ed., 2016,128, 10 3464 4. J. Phys. Chem. C., 2013, 17 (48), 25837–25844
5. Outreach activities:
In a project supported by the Stephenson Institute for Renewable Energy at the Univeristy of Liverpool we have built a solar hydrogen dolls house! This interactive display has been used for multiple events to demonstrate how to overcome the intermittent nature of solar energy. Half the house uses PV panels to provide power to the kitchen cooker and lights, but when the night comes the lights go out! The other part of the house uses PV panels to provide the power for the electrolysis of water to produce hydrogen and oxygen which can be stored in tanks in the garden. At night the doll family can use the hydrogen in a fuel cell to provide enough power to drive a stereo system, disco lights and disco ball allowing them to party the night away!