Highly Selective Photocatalytic Aerobic Oxidation of Methane to Oxygenates with Water over W‐doped TiO₂

Abstract

Highly selective conversion of methane to oxygenates with O 2 as a green oxidant remains a great challenge. It is still difficult to suppress the generation of CO x (x = 1, 2) as undesired byproducts due to unavoidable overoxidation reaction. Hence, tungsten-doped (W-doped) TiO 2 photocatalysts were designed with a tunable band structure for photocatalytic oxidation of methane to C 1 oxygenates using O 2 at low temperature (30 °C). The W-doping effectively modified the electronic and band structure of pristine TiO 2 to enhance photocatalytic perform-ance. Liquid oxygenates productivity could reach as high as 12.2 mmol g À 1 with high selectivity of 99.4 %. Moreover, CO x selectivity was effectively decreased from 21.2 % over TiO 2 to 0.6 % for W-doped catalyst. Detailed characterizations further disclosed that W-doping not only enhanced light absorption, but also promoted the separation of photo-generated carriers to improve methane conversion. This work provides new insights into the design of highly efficient photocatalysts for methane oxidation.

Selective Photocatalytic Oxidation of Methane to Oxygenates over Cu–W–TiO2 with Significant Carrier Traps

“…The lifetime of photogenerated carriers is usually as low as 10 –9 s while that for chemical reactions over the catalyst surface is in the range of 10 –8 –10 –3 s. ,, The charge recombination inevitably decreases the availability of the desirable photocatalytic activity. Many efforts have been devoted to prohibit the recombination of photogenerated carriers by electronic or band structure engineering, while metal doping and defect engineering provide two effective approaches to adjust carrier separation, transfer, and recombination. − Metal doping and surface oxygen vacancies as electron traps can effectively inhibit the carrier recombination. Zhang et al showed that Cu-doped TiO 2 with abundant vacancies exhibited outstanding photocatalytic nitrogen fixation performance .…”

Modulating the tunable interfacial charge transfer of Z-scheme TiO2/CdS with Ti–S bonds for enhanced glucose photoreforming

“…For n-type semiconductors, the E fb is 0.1 eV more positive than the conduction band potential ( E CB ). 44 Therefore, the E CB of TiO 2 and CdS were discerned to be −0.40 and −0.79 eV ( vs. NHE), respectively. According to the formula of E VB = E CB + E g , the potential of the valence bands ( E VB ) of TiO 2 and CdS were determined to be 2.81 and 1.66 eV, respectively.…”

“…For n-type semiconductors, the E  is 0.1 eV more positive than the conduction band potential (E CB ). 44 Therefore, the E CB of TiO 2 and CdS were discerned to be −0.40 and −0.79 eV (vs. NHE), respectively.…”

Effective SrWO4/TiO2 Heterojunction with Enhanced Carriers Separation and Transfer for Photocatalytic Methane Oxidation

“…The characterization diffraction peaks at 27.7°, 30.0°, 33.2°, 45.2°, 47.6°, 51.8°, 55.9°, 57.2° and 72.8° were attributed to SWO (Figure S1) [12a] . As shown in Figure 1b, the pristine TiO 2 showed several vibration modes of 142 cm −1 (E g ), 397 cm −1 (B 1g ), 515 cm −1 (A 1g +B 1g ) and 636 cm −1 (E g ) [14] . The characteristic signals of SWO could be observed at 74, 102, 336, 799 and 921 cm −1 ascribed to B g (ν evt.…”