Selective photocatalytic conversion of methane into carbon monoxide over zinc-heteropolyacid-titania nanocomposites

Abstract

Chemical utilization of vast fossil and renewable feedstocks of methane remains one of the most important challenges of modern chemistry. Herein, we report direct and selective methane photocatalytic oxidation at ambient conditions into carbon monoxide, which is an important chemical intermediate and a platform molecule. The composite catalysts on the basis of zinc, tungstophosphoric acid and titania exhibit exceptional performance in this reaction, high carbon monoxide selectivity and quantum efficiency of 7.1% at 362 nm. In-situ Fourier transform infrared and X-ray photoelectron spectroscopy suggest that the catalytic performance can be attributed to zinc species highly dispersed on tungstophosphoric acid /titania, which undergo reduction and oxidation cycles during the reaction according to the Mars–van Krevelen sequence. The reaction proceeds via intermediate formation of surface methyl carbonates.

Design of core–shell titania–heteropolyacid–metal nanocomposites for photocatalytic reduction of CO2 to CO at ambient temperature

“…Recently, we developed zinc-modied heteropolyacid-titania nanocomposites, which exhibit selective carbon monoxide production from methane at ambient temperature. 38 In the present study, we report for the rst time that the specically designed Zn-HPW/TiO 2 core-shell systems exhibited high photocatalytic activity in the selective conversion of carbon dioxide to carbon monoxide in the presence of water. In situ study of the reaction mechanism by IR and XPS has provided important insights into the reaction mechanism.…”

The special route toward conversion of methane to methanol on a fluffy metal‐free carbon nitride photocatalyst in the presence of H 2 O 2

“…After the activation of CH 4 , the ÁCH 3 generated can be converted to CH 3 OH with its interaction with H 2 O, ÁOH, or ÁO 2 − via Equations (9) and (14) (1) and (2)), and could play a key role in CH 3 OH formation, as suggested in the scavenger tests ( Figure 6). As shown in Equations (15) and (16) Figure 8B). For the full-sunlight system, the H + could be primarily generated from the interaction between H 2 O 2 and h + , thus only a little trace of H 2 O was found in the corresponding methanol products (Figure 8A,C).…”

“…as catalysts and H 2 O 2 or/and O 2 as oxidizing agents. However, despite the numerous efforts with admirable progresses, the complexity and high cost of the excellent catalysts have limited their industrial utilization …”

“…However, despite the numerous efforts with admirable progresses, the complexity and high cost of the excellent catalysts have limited their industrial utilization. [13][14][15][16] Photocatalytic oxidation of CH 4 to CH 3 OH, as an alternative approach, was first proposed by Noceti et al in 1997 [17][18][19] and has received increasing attention in the recent 5 years. Semiconductor photocatalysts that have been studied for this specific conversion include WO 3 , 17,20 TiO 2 , 18 NiO 2 , 19 BiVO 4 , 21,22 Bi 2 WO 6 , 23 ZnO, and so on.…”

Embedded carbon in a carbon nitride hollow sphere for enhanced charge separation and photocatalytic water splitting

“…Photocatalysis is an alternative and capable pathway to mitigate the consequence of the intensive fossil fuel consumption in many potential areas, including water splitting for hydrogen evolution, [1][2][3] carbon dioxide photoreduction, 4,5 nitrogen fixation [6][7][8][9] and methane upgrade. [10][11][12][13][14][15] The key is the development of an efficient photocatalyst. Amongst various photocatalysts, visible-light responsive graphitic carbon nitride (C 3 N 4 ) has recently emerged as a promising candidate due to its good activity and remarkable chemical stability.…”