Antimony-Doped Tin Oxide Catalysts for Green and Sustainable Chemistry

Abstract

Antimony dopants in tin oxide (SnO 2 :Sb) occupy part of the Sn sites in the crystal lattice to be dispersed at an atomic level. The resulting generation of conduction band electrons gives rise to high electric conductivity and strong optical absorption in the near-infrared region. Chemically, SnO 2 :Sb possesses electrocatalytic activities for the two-electron oxygen reduction reaction (2e − -ORR) with an extraordinary low affinity for H 2 O 2 and one-electron water oxidation reaction (1e − -WOR). Owing to these unique properties, SnO 2 :Sb is currently finding its applications for green and sustainable chemistry. This Perspective outlines the fundamentals and applications of SnO 2 :Sb. The fundamental parts deal with the three-dimensional single-atom-catalyst-like character of SnO 2 :Sb and the electrocatalytic activities for 2e − -ORR and 1e − -WOR. In the subsequent application parts, SnO 2 :Sb-catalyzed electrochemical and photocatalytic reactions including hydrogen peroxide synthesis, lowtemperature oxidative organic transformations, and decomposition of organic water pollutants are described with the photothermal catalytic reactions. Finally, the conclusions and future prospects are summarized.Perspective pubs.acs.org/JPCC

Three-Dimensional Plasmonic Photocatalyst Consisting of Faceted Gold Nanoparticles and Radial Titanium(IV) Oxide Heteromesocrystals

“…In the photoreaction region, 2-naphthol adsorbed on the surface of Au NPs and/or the interface with TiO 2 is oxidized by the hot holes left in Au NPs*, while the electrons in Au NPs efficiently reduce O 2 due to the electrocatalytic activity for 2e – -ORR. Further, the SnO 2 head of the Au/rad-TiO 2 HEMC can also enhance the charge separation and act as a reduction center because of its electrocatalytic activity for 2e – -ORR …”

“…Further, the SnO 2 head of the Au/rad-TiO 2 HEMC can also enhance the charge separation 31 and act as a reduction center because of its electrocatalytic activity for 2e − -ORR. 32 As an analog with the present photocatalyst, rad-TiO 2 MCs consisting of anatase TiO 2 NRs (rad-A-TiO 2 MCs) were synthesized at 453 K by a glycol-assisted solvothermal method 33 and by a hydrothermal method at 393 K. 34 Interestingly, rad-A-TiO 2 MCs have been reported to show high UV-light activity for aerobic decomposition of phenol, 33 oxidation of methyl ethyl ketone in air, 35 and oxidation of benzene to CO 2 and CO. 36 Also, Cabral and co-workers have shown that rad-A-TiO 2 MCs exhibit photocatalytic activity for degradation of methylene blue exceeding that of P-25, 37 which is well known to have high photocatalytic activity for various reactions. The authors have shown that the photocatalytic activity drastically decreases with the phase transformation to rutile upon heating above 750 K. This high activity of rad-A-TiO 2 MCs under UV-light irradiation can be basically ascribed to the anatase crystal structure with the ability for ORR 38 in addition to the effective light-harvesting property.…”

Hydrogen Peroxide Production by Inorganic Photocatalysts Consisting of Gold Nanoparticle and Metal Oxide toward Oxygen Cycle Chemistry

“…An effective means to improve the catalytic performance is alloying Au with other metals such as Ag , and Pd . Also, antimony-doped tin oxide is a very promising nonprecious MO due to the high activity for 2e – -ORR, low affinity for H 2 O 2 , extreme robustness, and the applicability to the electrochemical production of H 2 O 2 …”

“…74 Also, antimony-doped tin oxide is a very promising nonprecious MO due to the high activity for 2e − -ORR, low affinity for H 2 O 2 , extreme robustness, and the applicability to the electrochemical production of H 2 O 2 . 75 The development of all-solid-state Z-scheme-type photocatalysts is a fascinating approach to achieve efficient artificial photosynthesis. 76 A Z-scheme-type photocatalyst consisting of MnIn 2 S 4 /WO 3 co-doped with Yb and Tm has recently been reported for the H 2 O 2 photosynthesis.…”

Recent progress in electrocatalytic selectivity in heterogeneous electro-Fenton processes

“…The resulting catalyst delivered electrocatalytic activities for the 2e − ORR with an extraordinarily low affinity for H 2 O 2 . 87 Naya et al found that Sb doping into SnO 2 brought in a volcano-type relation between the 2e − ORR activity and doping levels with x Sb = 10.2 mol% being the best. DFT simulations highlighted the importance of an isolated Sb atom due to the enhancement of O 2 adsorption, decrease in the activation energy, and lowering of the absorptivity of H 2 O 2 .…”