Selective laser enhanced photocatalytic conversion of CO 2 into methanol A.H. Yahaya a , M.A. Gondal b, * , A. Hameed c a Chemistry Department, University of Malaya, 50603 Kuala Lumpur, Malaysia b Laser Research Laboratory, Physics Department, King Fahd University of Petroleum and Minerals, KFUPM, Dhahran, 31261, Saudi Arabia c Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia Received 25 September 2004; in final form 25 October 2004 Available online 11 November 2004 Abstract Selective photocatalytic reduction of CO 2 into methanol, using 355 nm UV laser as a light source, has been studied for the first time. An alternate route for the photocatalytic reduction of CO 2 , based on thermodynamic viability of the process, has been sug- gested. It was observed that the formation of methanol from CO 2 is a reversible process and the methanol produced during the pho- tocatalytic process degrades to generate hydrogen and CO 2 again; which hampers the over all conversion rate. The measurements on pH and hydrogen production during the course of photocatalytic reduction were valuable in explaining the conversion process. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction CO 2 gas is one of the major contributors to the green house effect and thus one of the primary causes of global warming. The atmospheric concentration of CO 2 has in- creased during last century due to rise in consumption of fossil fuel to run automobile, heat homes, and to power factories. The average concentration of CO 2 in the atmosphere has increased by 30% during the last millen- nium, which has further accelerated the global warming; the average temperature of the globe has risen by 0.5 °C over this period [1,2]. In order to avoid the serious consequences of global warming, strong action is required at the international level. Countries around the world have expressed their firm commitments to strengthening their responses to climate changes and to reduce green house gas emis- sions. In this context, the Kyoto Protocol of United Nations Framework Convention on Climate Change mandated a return of CO 2 emission levels to those of 1990 and to cut the green house emissions to 50%, in the future. To solve the CO 2 problem on permanent basis would require transforming CO 2 into some useful non-toxic compounds such as methanol. The conversion of CO 2 to high valued methanol and hydrogen will be helpful to humanity, the environment, and the global cli- matic change. Another issue which nations are facing is the energy demand. This demand is increasing at a much faster rate due to the rise in world population and indus- trial development. To overcome the environmental problems related to green house gas emissions and to fulfill the energy needs of future generations, research efforts are underway to develop sustainable and renewa- ble energy sources, which are environmentally friendly. Therefore, the transformation of CO 2 into useful prod- ucts like methanol, hydrogen, and methane is highly desirable. However, in this Letter, we make no claim that this process will be economically viable. Future studies should explore the commercial aspects of this method. 0009-2614/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.cplett.2004.10.109 * Corresponding author. Fax: +96638604281. E-mail address: magondal@kfupm.edu.sa (M.A. Gondal). www.elsevier.com/locate/cplett Chemical Physics Letters 400 (2004) 206–212