Significance

An efficient solar process for the one-step conversion of CO₂ and H₂O to C⁵⁺ liquid hydrocarbons and O₂ would revolutionize how solar fuel replacements for gasoline, jet, and diesel solar fuels could be produced and could lead to a carbon-neutral fuel cycle. We demonstrate that this reaction is possible in a single-step process by operating the photocatalytic reaction at elevated temperatures and pressures. The process uses cheap and earth-abundant catalytic materials, and the unusual operating conditions expand the range of materials that can be developed as photocatalysts. Whereas the efficiency of the current system is not commercially viable, it is far from optimized and it opens a promising new path by which such solar processes may be realized.

Abstract
A one-step, gas-phase photothermocatalytic process for the synthesis of hydrocarbons, including liquid alkanes, aromatics, and oxygenates, with carbon numbers (Cn) up to C₁₃, from CO₂ and water is demonstrated in a flow photoreactor operating at elevated temperatures (180–200 °C) and pressures (1–6 bar) using a 5% cobalt on TiO₂ catalyst and under UV irradiation. A parametric study of temperature, pressure, and partial pressure ratio revealed that temperatures in excess of 160 °C are needed to obtain the higher Cn products in quantity and that the product distribution shifts toward higher Cn products with increasing pressure. In the best run so far, over 13% by mass of the products were C⁵⁺ hydrocarbons and some of these, i.e., octane, are drop-in replacements for existing liquid hydrocarbons fuels. Dioxygen was detected in yields ranging between 64% and 150%. In principle, this tandem photochemical–thermochemical process, fitted with a photocatalyst better matched to the solar spectrum, could provide a cheap and direct method to produce liquid hydrocarbons from CO₂ and water via a solar process which uses concentrated sunlight for both photochemical excitation to generate high-energy intermediates and heat to drive important thermochemical carbon-chain-forming reactions.

http://www.pnas.org/content/113/10/2579.abstract

http://cen.acs.org/articles/94/i9/Sunlight-helps-power-high-energy.html

中文报道（化学家逆转燃烧过程，用水和CO₂合成液态烃燃料）链接：
http://mp.weixin.qq.com/s?__biz=MzAwOTExNzg4Nw==&mid=409364394&idx=1&sn=534203a1bad4ecb17c215fa8701bd017&scene=0#wechat_redirect