Synthetic strategies to nanostructured photocatalysts for CO₂reduction to solar fuels and chemicals

Abstract

Artificial photosynthesis represents one of the great scientific challenges of the 21 st century, offering the possibility of clean energy through water photolysis and renewable chemicals through CO 2 utilisation as a sustainable feedstock. Catalysis will undoubtedly play a key role in delivering technologies able to meet these goals, mediating solar energy via excited generate charge carriers to selectively activate molecular bonds under ambient conditions. This review describes recent synthetic approaches adopted to engineer 10 nanostructured photocatalytic materials for efficient light harnessing, charge separation and the photoreduction of CO 2 to higher hydrocarbons such as methane, methanol and even olefins. 65 manufacture involves steam or catalytic cracking of naphtha, gasoil and condensates to hydrocarbon mixtures followed by distillation. Cracking crude oil to produce ethene or propene is thermodynamically unfavourable (∆G ≈ +100 kJmol -1 ), requiring high temperatures (> 600°C) to overcome the huge activation 70 barriers to C-C cleavage (280 kJmol -1 for kerosene conversion 29 ). Hence steam cracking is the most energyconsuming process in chemistry, accounting for 8% of the sector's primary energy use and annual CO 2 emissions of 180-200 Mt. 28 75 Brief history and fundamental principles of photocatalytic materials for CO 2 reductionRenewable solar energy, harnessed via innovative catalysts and reactors, has the potential to photoreduce linear CO 2 molecules by breaking the C=O bonds to form C-H bonds and then to yield 80 Plastics Advances in nanomaterials synthesis offer new routes to solar fuels and chemicals from CO 2 as a sustainable chemical feedstock

g-C3N4-Based Nanomaterials for Visible Light-Driven Photocatalysis

“…Note that the direct activation of reactants and intermediates through light absorption is the realm of photochemistry; in establishing whether a transformation is truly photocatalytic it is therefore crucial to establish that photons are absorbed by the catalyst rather than adsorbates [17,18]. In the photocatalytic production of so-called 'solar fuels', photoexcited charge carriers drive the conversion of water and CO2 into H2, CO, CH4, CH3OH and related oxygenates and hydrocarbons [19][20][21]. Such processes parallel those in nature wherein sunlight absorbed by chlorophyll in plants promotes starch and oxygen production from carbon dioxide and water), and are hence termed artificial photosynthesis ( Figure 1).…”

Nano/microsized TiO₂ composite photocatalysts for environmental purification

“…33), 34) E-glass fiber, which has a low-alkaline composition, is one of the many mass-produced glass fibers. The E-glass fiber is corroded by acid solution and forms a porous structure: Al 2 O 3 , B 2 O 3 , and alkaline metal and alkali earth Journal of the Ceramic Society of Japan 126 [8] 625-631 2018 metal ions are dissolved from the fiber, and the porous SiO 2 structure is left behind. In this work, a porous glass cloth was prepared by the acid leaching of an E-glass cloth, and it was then used as a TiO 2 support.…”

“…8)10) The reaction mechanism is explained as follows. When ultraviolet (UV) light illuminates the photocatalyst, electron and hole pairs are generated that respectively reduce and oxidize adsorbates on the catalyst surface and generate radical species.…”

Wheat bran valorisation: Towards photocatalytic nanomaterials for benzyl alcohol photo-oxidation

“…Among various semiconductorbased photocatalysts, TiO 2 is one of the most attractive photocatalysts owing to its outstanding photocatalytic activity, high thermal and chemical stability, non-toxicity, cost effectiveness and the strong oxidizing power of the photogenerated holes. Massive investigations related to TiO 2 photocatalysts have been reported in different applications in the last decades, including chemicals and fuels production from CO 2 reduction (Adachi et al, 1994;Chen et al, 2015;Yu et al, 2014), decontamination of water (Herrmann et al, 1999;Hoffmann et al, 1995;Yang et al, 2008), organic synthesis (Colmenares et al, 2016;Higashimoto et al, 2009;Hubert et al, 2010;Ohno et al, 2003b) and production of H 2 from water splitting (Chen et al, 2010;Ni et al, 2007). However, the use of pure TiO 2 photocatalyst is limited by its large band gap (3.2eV, anatase crystalline phase) which requires light with wavelength l < 387 nm for the excitation of electrons from the valence to the conduction band, resulting that only 5% of the solar irradiation can be utilized for the photocatalytic process.…”