Highly Efficient Ambient Temperature CO₂ Photomethanation Catalyzed by Nanostructured RuO₂ on Silicon Photonic Crystal Support

Abstract

Sunlight‐driven catalytic hydrogenation of CO2 is an important reaction that generates useful chemicals and fuels and if operated at industrial scales can decrease greenhouse gas CO2 emissions into the atmosphere. In this work, the photomethanation of CO2 over highly dispersed nanostructured RuO2 catalysts on 3D silicon photonic crystal supports, achieving impressive conversion rates as high as 4.4 mmol gcat−1 h−1 at ambient temperatures under high‐intensity solar simulated irradiation, is reported. This performance is an order of magnitude greater than photomethanation rates achieved over control samples made of nanostructured RuO2 on silicon wafers. The high absorption and unique light‐harvesting properties of the silicon photonic crystal across the entire solar spectral wavelength range coupled with its large surface area are proposed to be responsible for the high methanation rates of the RuO2 photocatalyst. A density functional theory study on the reaction of CO2 with H2 revealed that H2 splits on the surface of the RuO2 to form hydroxyl groups that participate in the overall photomethanation process.

FeO–CeO2 nanocomposites: an efficient and highly selective catalyst system for photothermal CO2 reduction to CO

“…The FeCe-x nanocomposite catalysts were prepared by H 2 reduction of Fe(OH) 3 -Ce(OH) 3 precursors at temperatures in the range of 200-600°C. Briefly, precursors were prepared via a simple precipitation reaction.…”

“…Modern societies are highly dependent on fossil fuel energy for electricity generation and transportation. Combustion of fossil fuels for energy releases CO 2 into the atmosphere, thereby causing global warming and a plethora of associated environmental problems [1][2][3] . To curb anthropogenic CO 2 emissions, researchers are now actively exploring different catalytic approaches for converting CO 2 into fuels and valuable commodity chemicals [4][5][6][7][8] .…”

“…As a form of CO 2 sequestration, these catalytic approaches are particularly desirable, as they can generate economic value from CO 2 (thereby transforming CO 2 into a resource rather than an environmental problem requiring mitigation) 1,4,9 . However, transforming CO 2 into other useful compounds such as CO, CH 3 OH, HCOOH, CH 4 , and C 2+ hydrocarbons is challenging, requiring activation of strong C=O bonds 10 . Accordingly, the rates of CO 2 reduction via photocatalytic methods and electrocatalytic methods are currently too low to justify serious consideration from industry 11,12 .…”

“…A further challenge with CO 2 reduction is achieving high selectivity for a specific product, which is highly desirable since it eliminates the need for separation of different reaction products. Most catalytic technologies for CO 2 reduction developed to date are based on hydrogenation approaches, which typically utilize the Sabatier reaction (CO 2 + 4H 2 → CH 4 + 2H 2 O) and/or the reverse water-gas shift (RWGS, CO 2 + H 2 → CO + H 2 O) 3,13 . While CO 2 can be converted into CH 4 and H 2 O via the Sabatier reaction, activation of CH 4 for further conversion into other higher-value chemicals requires a considerable energy input 14,15 ; thus, this approach for CO 2 conversion to value-added chemicals is not practical.…”

“…Herein, a series of novel FeO-CeO 2 nanocomposite catalysts were prepared by H 2 reduction of Fe(OH) 3 -Ce (OH) 3 precursors at temperatures between 200 and 600°C (the catalysts are denoted as FeCe-x, where x is the reduction temperature). The Fe:Ce molar ratio in the FeCe-x catalysts was varied from 1:2 to 3:1.…”