CO2 and the Environment
The threat of climate change and its consequent humanitarian catastrophes, have put the development of carbon capture, storage and utilisation technologies firmly on the scientific and political agenda. It is agreed that the global average temperature should not be allowed to rise by more than 20 °C above its pre-industrial level, which means cutting global greenhouse gas emissions by 50% compared to 1990 levels. As a result, in the Climate Change Act 2008 the UK has committed to cutting its greenhouse gas emissions by at least 80% by 2050. It is therefore essential that new methods are designed to treat CO2 gas from the air and identify long-term storage solutions and/or removal/conversion treatments.
Limitations of current methodology
Current CO2 removal methods concentrate primarily on CO2 storage, rather than its conversion and use. For example, one of the most promising solutions for the long-term storage of atmospheric CO2 is its sequestration into deep-sea carbonate minerals. However, this may well lead to rapid local acidification of the marine environment with potentially harmful, but as yet unknown, long-term effects.
The field of catalysis is currently dominated by metal-oxide chemistry and most technologies for alternative energy sources (fuel cells, solar energy) or carbon capture are based on oxide materials. However, the reducing capabilities of oxides rely mostly on defects and doping and manipulation of the catalysts’ structures/compositions to obtain the required surface redox properties for any catalysed reaction can be both difficult, due to the inherent stability of the oxide anion, and costly, because of the frequent need for rare metals (eg. Au, Pt). Sulfides, on the other hand, are excellent natural reducing agents owing to their variable oxidation states. The reactivity and selectivity of the material towards the conversion of CO2 can be enhanced further through the choice of transition metals. Thus, the novel bio-inspired use of transition metal sulfides, with their proven track-record in the reduction and conversion of CO2, makes these materials ideal candidates for the capture and catalysis of CO2 into product.
Our aim is therefore to exploit the multi-valency of both transition metals and sulfide anions to develop finely-tuned catalysts with the correct reactivity/selectivity for the activation and conversion of CO2. Other inorganic metal and metal oxide catalysts will also be investigated that exploit the exceptionally high surface area to volume ratios of highly active nanoceramic.