Catalysts for photochemical carbon dioxide reduction to green fuels and chemicals

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Climate change and the greenhouse effect are mainly related to the increasing concentration in the atmosphere of a molecule that traps heat, namely CO2 or carbon dioxide. As a strategy to address CO2 increasing levels, carbon capture and utilisation (CCU) is gaining more attention in scientific research. This project applies photochemical catalysis to activate and transform carbon dioxide into dense energy carriers and chemical precursors, including carbon monoxide, alcohols and acids.To drive the photocatalytic reduction of carbon dioxide suitable semiconducting photocatalysts have to be developed. When these interact with solar light irradiation, the sun's energy is transferred to the semiconductor creating excited states which can be used in the reduction of carbon dioxide to valuable chemicals. This research aims to understand the semi-conductor/catalyst excited states and electronic structures and delineate structure-performance relationships through modifications. The work targets low-temperature and pressure processes, using metal/metal oxide/sulfide materials as both absorbers and catalysts.The photochemical mechanisms for carbon dioxide reduction are complex and more research is needed to understand factors controlling rates, selectivity and product formation pathways. This project will develop stable photocatalysts that can help elucidate the mechanism of photocatalytic CO2 reduction and in the second stage, improve the solar-to-chemical conversion efficiencies. In the first phase, UV light-absorbing catalysts such as SrTiO3 (strontium titanate) will be modified with copper (Cu) nanoparticles. Inexpensive, earth-abundant Cu is considered the best candidate due to its strong track record as a catalyst for MeOH (methanol) synthesis in thermal reactions and its track record in electrocatalysis producing C2+ products from carbon dioxide. The thesis will compare different means to produce copper nanoparticles, including electrosynthesis, photoredox synthesis and chemical synthesis. The particle-catalyst surface chemistry will be explored using techniques such as atomic layer deposition and by exploiting chemical functionality/reactivity. Catalyst-particle interfaces will be studied and characterized and catalytic activity tested photochemically under a range of different conditions.This strategy will give us more insight into the factors that govern product selectivity and catalyst activity and will result in an efficient photocatalytic system based on earth-abundant materials for CO2 reuse. This specific target performance has the impact to give a large contribution to addressing one of the main challenges of this century and support society and the ESPRC to transition towards a low- carbon future while protecting the environment. As such, this project falls within the EPSRC Energy research area.