Enhanced photocatalytic carbon dioxide reforming of methane to fuels over nickel and montmorillonite supported TiO2 nanocomposite under UV-light using monolith photoreactor

Photocatalytic and Thermocatalytic Conversion of Methane

“…The preparation of syngas (CO, H 2 ) from photocatalytic CRM is also an important research topic, and many researchers have been making unremitting efforts to improve the quantum efficiency of the reaction process. [ 136–141 ] For example, Hu and co‐workers reported an efficient visible‐light photocatalytic CRM process by combining a Pt/black TiO 2 catalyst with the light‐reflecting surface of a SiO 2 substrate. [ 142 ] This process exhibits a high quantum efficiency of 32.3% at 550 °C and 57.8% at 650 °C under visible‐light irradiation ( Figure a,b).…”

Powering the next industrial revolution: transitioning from nonrenewable energy to solar fuelsviaCO2reduction

“…Currently, this may be achieved via one of two general pathwayseither through indirect or direct thermoconversion, with several examples of each appearing regularly in scientic literature. [63][64][65][66][67][68] Direct thermoconversion makes use of photonic thermomaterials which readily absorb incident light and convert this energy to heat, creating a localised temperature gradient at the site of reactivity. Conversely, indirect thermoconversion employs the use of solar concentrators which focus incident light energy (and where desired, lter the radiation to utilise a more narrow wavelength range) to a more concise area in order to heat the bulk reaction media.…”

“…To realise this goal, several attempts have been made to create articial photosynthesis wherein incident light energy facilitates direct photoconversion of CO 2 into viable solar fuels. 63,95,[147][148][149][150][151][152][153][154][155] When considering the general mechanism of chemical reactivity of Cat4 on a quantum level, there are striking similarities to Cat2, especially when comparing to an integrated PEC device. While the following delineation could be qualied as a generality, we will consider such devices which do not require a bias potential or possess a dedicated photoelectrode as Cat4 systems for solar fuel generation.…”

In Situ Investigation of Charge Performance in Anatase TiO2 Powder for Methane Conversion by Vis–NIR Spectroscopy

“…First, it was suggested that CH 4 was able to be directly oxidized by photoexcited holes (e.g., in the form of O – species) in the valence band (VB) of TiO 2 or TiO 2 -based materials to form the CH 3 • radical and OH – 16 , 17 or H + . 8 , 17 − 22 Also, Yoshida et al extrapolated knowledge from thermal catalysis and suggested that O – (photoexcited hole) directly extracts a H • radical from CH 4 . 23 In the case of OH – , the electron density mainly resides on the oxygen and therefore can be regarded as a “filled” hole in/near the VB.…”

“…Between the two extremes discussed above, Tahir et al suggested that both direct oxidation of CH 4 by valence band holes and indirect oxidation by OH • radicals can take place during TiO 2 -based photocatalysis. 17 However, Tahir et al were studying dry reforming of methane (DRM) and therefore the OH • species they proposed likely involved a lattice oxygen, rather than originating from H 2 O. In addition to the methane activation mechanisms discussed thus far, Lang et al recently reported that the first step occurring during nonoxidative coupling of methane over Au-loaded TiO 2 was CH 4 reduction by photoexcited electrons in Au to form the CH 3 – anion and atomic H, 27 though it is not clear whether this mechanism might also be applicable for pure anatase TiO 2 .…”