Noble Metal-Free Inorganic Photocatalyst Consisting of Antimony-Doped Tin Oxide Nanorod and Titanium oxide for Two-Electron Oxygen Reduction Reaction.

This study reports a noble metal-free robust inorganic photocatalyst for H2 O2 synthesis via two-electron oxygen reduction reaction (ORR). Antimony-doped tin oxide nanorods were heteroepitaxially grown from rutile TiO2 seed crystals with an orientation of (001)ATO //(001)TiO2 (ATO-NR//TiO2 ,//denotes heteroepitaxial junction) by a hydrothermal method. UV-light irradiation of ATO-NR//TiO2 particles stably and continuously produces H2 O2 from aerated aqueous solution of ethanol. Electrochemical measurements using rotating electrodes show that Sb-doping into SnO2 greatly enhances the electrocatalytic activity for two-electron ORR. The striking photocatalytic activity of ATO-NR//TiO2 stems from the effective charge separation, electrocatalytic activity for two-electron ORR, low catalytic activity for H2 O2 decomposition, and extraordinary robustness.

Highly Active and Renewable Catalytic Electrodes for Two-Electron Oxygen Reduction Reaction.

This study has shown that antimony-doped tin oxide (ATO) works as a robust "renewable catalyst" for the electrochemical synthesis of hydrogen peroxide (H2O2) from water and oxygen. Antimony doping into SnO2 gives rise to remarkable electrocatalytic activity for two-electron oxygen reduction reaction (2e--ORR) by water with a volcano-type relation between the activity and doping levels (xSb). Density functional theory simulations highlight the importance of an isolated Sb atom of ATO inducing the high activity and selectivity for 2e--ORR due to the effects of O2 adsorption enhancement, decrease in the activation energy, and lowering the adsorptivity of H2O2. Electrolysis by a normal three-electrode cell using ATO (xSb = 10.2 mol %) at -0.22 V (vs reversible hydrogen electrode) stably and continuously produces H2O2 with a turnover frequency of 6.6 s-1. This remarkable activity can be maintained even after removing the surface layer of ATO by argon-ion sputtering.

Positron-electron correlation-polarization potential model for positron binding in polyatomic molecules.

Positron binding energies (PBEs) of 41 polyatomic molecules were calculated using the positron-electron correlation-polarization potential (CPP) approach and compared with experimentally measured values. In this approach, the short-range positron-electron potential is modeled using the density-functional expression, whereas the long-range potential is approximated by the attractive polarization potential. The positron-electron CPP model based on local-density approximation yields larger PBEs than experimental values; however, the calculated values can be substantially improved by introducing generalized gradient approximation. We also investigated the conformational dependence of PBEs for representative molecules.