Nanocrystalline Water Splitting Photodiodes II; Device Engineering, Integration and Scale-up

Objectives The objectives of the research programme have been broken down as follows. The primary objective of this project is to deliver inexpensive, scaled-up, efficient (> 7% solar energy conversion efficiencies; quantum yields > 30%), visible-light absorbing nanocrystalline semiconductor photocatalyst diode demonstrators for distributed fuel production and utlilisation via household installations. This will be achieved by the following objectives: * To create test semiconductor photochemical diodes and assess and optimise their performance * To utilise novel and more established routes to produce highly active, visible light absorbing, nanoparticulate semiconductor metal oxide photocatalysts * To synthesise, deposit and characterise novel metal and metal oxide nano-catalysts onto the water oxidation side of the photocatalyst supports. * To convert the most promising photocatalyst nanopowders (made via pilot plant CHFS) or commercial semiconductor powders into coatings. * To assess the ability of the functionally graded photodiodes for water reduction and oxidation * To coat nanoparticles of known catalysts (e.g. Pt or Ni) onto the water reduction side (for hydrogen gas production) of the photocatalyst films using photo, sol gel, thermal, cold gas spray, sputtering or related deposition techniques. * To optimise the performance of the devices through careful control of the interfaces * To develop an engineering model of the photochemical device in order to inform design decisions based on mechanical, thermal, hydrodynamic and charge (electronic and ionic) considerations. * To perform an applications feasibility assessment, including investigation into how photocatalyst diode demonstrators can be integrated with working fuel cell devices for household use, to provide constant or intermittent power as well how to operate in conjunction with solar water heating and combined heat and power (CHP) devices. * To test a device in combination with a fuel cell, hydrogen storage and simulated domestic power demand to develop and refine control and operational methodologies and examine physical integration to address water and thermal management. * To develop a system model for the sizing of units and operational optimisation for different applications and system configurations. * To test the working prototype in an actual domestic, distributed energy production, storage and usage environment. * To perform a life-cycle assessment of the device and system as well as a techno-economic (leading to cost model) analysis to inform commercialisation and investment strategies at the end of this phase.

Impact Summary The beneficiaries range from (i) the general public and (ii) the Government and public sector, to (iii) a wide variety of industries and even (iv) charities and voluntary organisations. (i) General Public With depletion of the world's fossil fuels, industrialised countries must seek alternative energy sources before the costs of such resources become prohibitive. Burning fossil fuels to create electricity as at present is a major contributor to global warming, releasing huge quantities of carbon dioxide gas. The inexpensive and green production of fuel using free solar energy from the sun will be able to contribute towards the overall energy requirements of households and industry over the next decades as the world moves away from total reliance on polluting fossil or potentially hazardous nuclear fuels. The devices chosen are planned to inexpensive to make, durable and long lived. This approach has the ability to produce all the energy needed by a household in one day from a volume of water less than a single toilet flush. It is also non polluting as the only byproduct from the combustion of hydrogen is water. (ii) Commercial Sector Not only will our project partners such as Tata Steel (formerly Corus), TWI or Teer benefit from the commercial development of demonstrator photodiodes on a huge scale, but the supporting industries such as Cristal Global or Johnson Matthey will benefit from the large scale use or production of novel, UV and visble-light active semiconductor photocatalysts or precious metals as part of the water splitting devices. Such materials or coatings research will also benefit industries developing metal supported dye sensitised solar cells and also self cleaning products, such as architectural steels, glass, tiles and paints (e.g. Cristal global). Energy companies will also benefit from the development of such devices which can be used to support the national grid particularly at times of high demand. (iii) Government/Public Sector The proposed technology only uses and produces water and therefore does not pollute the environment via the production of CO2 such as occurs with fossil fuels. With ever more stringent legislation put in place to guarantee a cascade of international agreements to reduce CO2 and other greenhouse gases to acceptable levels, viable routes to a proven reduction of fossil fuels are clearly of prime importance to policy makers and legislators. (iv) Third Sector More speculative beneficiaries of this research are charities and voluntary organisations. With climate change leading to more frequent weather-induced disasters, such as hurricanes, floods and droughts, the call on voluntary aid organisations is increasing rapidly and climate stabilisation (via use of methods which negate the need for polluting fossil fuel technologies) would alleviate this burden to sustainable levels. The ability to remotely generate energy from the sun using water splitting devices could also help for localised or remote energy generation in areas such as those with no access to grid power or in case of emergencies.