Adsorbed CO₂-Mediated CO₂ Photoconversion Cycle into Solar Fuel at the O Vacancy Site of Zirconium Oxide

Abstract

ZrO 2 photoreduces 13 CO 2 under ultraviolet−visible light to 13 C-product(s) negligibly affected by adventitious carbon. The dual-site reaction pathway was theoretically clarified from CO 2 to CO using monoclinic ZrO 2 , followed by multiple hydrogenation steps to methane over Ni nanoparticles. The oxygen vacancy (V O•• ) played essential roles, including the M-shaped CO 2 adsorption over the V O•• site and the direct occupation of the V O •• site by the dissociated O and/or hydroxy group from the hydroxycarbonyl species favorably on the ZrO 2 (111) surface. The rate-limiting step was for the regeneration of the V O•• site with an activation energy (E act ) of 2.6 eV, but the water desorption energy was greatly compensated by the CO 2 adsorption energy at the V O•• site, in contrast to the first-row transition-metal oxides. The COH and/or CO species transfer from ZrO 2 to Ni in a concerted mechanism was energetically favorable, and the apparent E act value from hydroxycarbonyl species to methane was reduced to 0.67 eV.

Photocatalytic CO2 Reduction Using Ti3C2Xy (X = Oxo, OH, F, or Cl) MXene–ZrO2: Structure, Electron Transmission, and the Stability

“…The formation rate was higher using CO 2 and H 2 in the previous paragraph because of the greater light intensity (500 mW cm –2 ) versus that using 13 CO 2 and H 2 (142 mW cm –2 ). The 12 CO ratio in the total CO ( 13 CO and 12 CO) was 30%, significantly higher than the 12 C ratio in the reactant 13 CO 2 (1.0%), suggesting that the reaction intermediate comprising 12 C was concentrated during the photocatalytic test starting from 12 CO 2 adsorbed on surface O vacancy (V O •• ) sites from air. − …”

“…12 CH 4 was likely derived from MXene decomposition and not the photocatalytic product. True intermediate species, e.g., O–C–OH, , was not detected in the FTIR spectrum (Figure a) due to the relatively short lifetime on the photocatalyst surface.…”

“…A 3 × 3 × 1 k-point mesh was used for the structural optimization, while a 1 × 1 × 1 k-point mesh was used for the calculations of electronic states. The Ti 3 C 2 X y hexagonal five layers model 20 exposing the X ligand (X = OH, F, or Cl) on both sides of the Ti 3 C 2 layer was used combined with the Zr 11 O 22 cluster based on the monoclinic phase ZrO 2 21 as a slab model with a vacuum spacing of 2.0 nm between the slabs in the direction perpendicular to the Ti 3 C 2 X y layer (Chart S1).…”

Infrared Fingerprints of the CO2 Conversion into Methanol at Cu(s)/ZrO2(s): An Experimental and Theoretical Study

“…As pointed out in Ref. [43][44][45][46], the most viable route to form CO on ZrO 2 consists of CO 2 adsorption at an oxygen vacancy, a step that is followed by the oxygen transferring to fill the vacant site. Upon formation on ZrO 2 surface, the primary interaction of CO occurs through the carbon atom (see Figure 2 (a)) with Zr 4 + centers, which has a CÀ O stretching mode located at 2129 cm À 1 and ṽcalc = 2167 cm À 1 .…”

Effect of oxygen vacancies and crystal phases in defective Pt/ZrO2−x on its photocatalytic activity toward hydrogen production

“…15,17,18 In particular, V O s not only narrow the bandgap of ZrO 2 but also play a critical role as trap sites for molecules and intermediate compounds. 19,20 The previously reported examples have already demonstrated that the photocatalytic performance can be improved through defect formation. However, the effect of crystal phases, which is one of the factors that most strongly influence photocatalytic reactions and is frequently discussed for nondefective metal-oxide photocatalysts, 21,22 has received less attention for defective ZrO 2−x .…”