Is water more reactive than H2 in photocatalytic CO2 conversion into fuels using semiconductor catalysts under high reaction pressures?

Why Is Water More Reactive Than Hydrogen in Photocatalytic CO2 Conversion at Higher Pressures? Elucidation by Means of X-Ray Absorption Fine Structure and Gas Chromatography–Mass Spectrometry

“…Methane was a dominant product under the conditions. In contrast, the formation rates followed a typical Langmuir-type dependence, i.e., they gradually increased as a function of reactants pressure under CO 2 + moisture at 0.12–0.80 MPa (Table 1 D, E, G) (Zhang et al, 2017 ). Minor CO and methanol were also produced under the conditions.…”

“…First, reported kinetic results are summarized. Both the reactions under CO 2 + H 2 and under CO 2 + moisture critically depended on the pressure of reactants using Pd/TiO 2 (Kawamura et al, 2017 ; Zhang et al, 2017 ). The formation rates of C-containing products under CO 2 + H 2 reached a local maximum at 0.40 MPa (0.12 MPa of CO 2 , 0.28 MPa of H 2 ) and drew a volcanolike dependence (Table 1 A, C).…”

“…The high-pressure photoconversion tests were performed in homemade stainless steel reactor equipped with quartz windows (Kawamura et al, 2017 ; Zhang et al, 2017 ). A mixed CO 2 /H 2 gas or CO 2 gas/moisture was introduced into the reactor.…”

Plasmonic photocatalysis applied to solar fuels

“…One may also speculate that it may simply not be formed as it is in the SC-based process and that H ○ + H ○ recombination simply does not occur in the gold-driven, plasmon-based process. In addition to the instability of the hydrogen molecule under plasmonic conditions, the absence of UV irradiation, which is known to enhance formation of defects on titania, 44,45 may also lower the possibility of CO2 adsorbing on titania. Under visible-only irradiation, CO2 adsorption and activation would thus be restricted to the gold surface, where it would more efficiently compete with H ○ , especially on dehydroxylated titania surfaces which likely lower the reverse spillover rate of H ○ .…”

Microwave, Ultrasound, and Mechanochemistry: Unconventional Tools that Are Used to Obtain “Smart” Catalysts for CO2 Hydrogenation

“…The chemical processes for CO 2 reutilization are catalytic [13][14][15], photocatalytic [16][17][18][19][20], electrocatalytic [21][22][23][24][25], or photoelectrocatalytic [18,26]. As a whole, the chemical reduction of CO 2 is a challenge from both the industrial and the catalytic point of view [27], but it is also a hot scientific topic, since CO 2 is an ideal C1 feedstock for producing different types of chemicals and, ultimately, fuels.…”