INTERNATIONAL COLLABORATION IN CHEMISTRY ENHANCING DIRECT PHOTOELECTROCHEMICAL CONVERSION OF CO2

半导体分散体通过光的作用将水分解成氧和氢，这通常被称为光电电解或光电催化，这是一个非常重要的发现，它导致了大量旨在分解水和减少二氧化碳的活动。分散半导体驱动这种氧化还原过程的能力取决于带边相对于氧化还原过程的电化学势的位置。尽管这些工艺确实可行，而且应用起来成本低廉，但到目前为止，产品的产量还不足以带来技术突破。尽管如此，光电催化过程的早期研究实际上已经导致了一些非常重要的技术成就，包括自清洁窗户、带有集成氧化还原穿梭的Grtzel太阳能电池和废物的光催化修复。化石燃料转换产生的二氧化碳排放量每年高达2.5x10^10公吨，由于它与全球变暖有关，因此对21世纪的环境构成了重大挑战。在京都协议之后，许多政府承诺减少温室气体排放；然而，全球能源需求正在增加，二氧化碳水平很可能实际上会增加。二氧化碳封存是一种解决方案，但它可能会产生能效成本。通过物理化学方法将二氧化碳转化为有用的燃料和化学原料，不仅减少了大气中的二氧化碳，还减少了对化石碳的依赖，提高了能源安全。这个拟议团队的成员此前曾报告说，光电催化将溶解的二氧化碳还原为一系列和两种碳产品，旨在开发一种可能的途径，从太阳能获得合成燃料。二氧化碳分子上加一个电子就会产生二氧化碳自由基阴离子。本种可能被质子化，导致甲酸盐；它可能与一氧化碳和碳酸盐不成比例，或者它可能二聚化提供草酸盐。因此，有一系列可能的机制可以将二氧化碳转化为液体燃料。通过甲酸盐的路径必须包括水；然而，以前在光电催化还原实验中观察到了在还原过程中不需要水参与的CO和二聚产物。仍然有一些关键问题需要解决，我们寻求在我们的合作方案中解决每一个共享新概念和材料的问题。

The splitting of water to form oxygen and hydrogen by the action of light upon a semiconductor dispersion, often termed photoelectrolysis or photoelectrocatalysis was a very important discovery , which lead a great deal of activity aimed at water splitting and CO2 reduction . The ability of a dispersed semiconductor to drive such redox processes is determined by the positions of the band edges in comparison to the electrochemical potentials of the redox processes. Although these processes do work and would be cheap technologies to apply, the yields of products have so far been insufficient to lead to a technological breakthrough. Despite this, early research on photoelectrocatalytic processes has in fact led to some very major technological achievements including self-cleaning windows , the Grtzel solar cell with integral redox shuttle and photocatalytic remediation of wastes .CO2 emissions from fossil fuel conversion amount to 2.5 x 10^10 metric tons of CO2 per annum yielding a significant environmental challenge for the 21st century due to its association with global warming. Following the Kyoto agreement many Governments were committed to a reduction in Greenhouse gas emission; however, energy demands are increasing globally and it is likely that CO2 levels will actually increase. CO2 sequestration is one solution, but it is likely to have an energy efficiency cost. Conversion of CO2 by physio-chemical means to useful fuels and chemical feedstocks, not only reduces CO2 in the atmosphere it reduces dependency on fossil carbons, increasing energy security. Members of this proposed team have previously reported the photo-electrocatalytic reduction of dissolved carbon dioxide to a range of one and two carbon products , aiming to develop a possible route to synthetic fuels from solar energy. The addition of one electron to a carbon dioxide molecule produces a carbon dioxide radical anion. This species may be protonated leading to formate; it may disproportionate to carbon monoxide and carbonate or it may dimerise giving oxalate. Consequently there are a range of possible mechanisms by which the CO2 may be converted to liquid fuels. The paths via formate must involve water; however both CO and dimerization products that do not require involvement of water in the reduction process have been previously observed in photo-electrocatalytic reduction experiments . There are still a number of key issues to be solved, and, we seek to address each of these sharing new concepts and materials in our collaborative programme.