Catalysis using gold nanoparticles supported on oxides has been under extensive investigation for many important application processes. However, how to tune the charge state of a given Au species to perform a specific chemical reaction, e.g. CO oxidation, remains elusive. Here, using first-principles calculations, we show clearly that an intrinsically inert Au anion deposited on oxygen-deficient TiO 2 (110) (Au@TiO 2 (110)) can be tuned and optimized into a highly effective single atom catalyst (SAC), due to the depletion of the d-orbital by substrate doping. Particularly, Ni-and Cu-doped Au@TiO 2 complexes undergo a reconstruction driven by one of the two dissociated O atoms upon CO oxidation. The remaining O atom heals the surface oxygen vacancy and results in a stable bow-shaped surface "O-Au-O" species; thereby the highly oxidized Au single atom now exhibits magnetism and dramatically enhanced activity and stability for O 2 activation and CO oxidation, due to the emergence of high density of states near the Fermi level. Based on further extensive calculations, we establish the "charge selection rule" for O 2 activation and CO oxidation on Au: the positively charged Au SAC is more active than its negatively charged counterpart for O 2 activation, and the more positively charged the Au, the more active it is.

The18 Ne(α,p) 21 Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the rp-process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus 22 Mg have been investigated by measuring the resonant elastic scattering of 21 Na+p. An 89 MeV 21 Na radioactive beam delivered from the CNS Radioactive Ion Beam Separator bombarded an 8.8 mg/cm 2 thick polyethylene (CH2)n target. The 21 Na beam intensity was about 2×10 5 pps, with a purity of about 70% on target. The recoiled protons were measured at the center-of-mass scattering angles of θc.m.≈175.2• , 152.2 • , and 150.5• by three sets of ∆E-E telescopes, respectively. The excitation function was obtained with the thick-target method over energies Ex( 22 Mg)=5.5-9.2 MeV. In total, 23 states above the proton-threshold in 22 Mg were observed, and their resonant parameters were determined via an R-matrix analysis of the excitation functions. We have made several new J π assignments and confirmed some tentative assignments made in previous work. The thermonuclear 18 Ne(α,p) 21 Na rate has been recalculated based on our recommended spin-parity assignments. The astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the 18 Ne(α,p) 21 Na rate significantly affects the peak nuclear energy generation rate, reaction fluxes, as well as the onset temperature of this breakout reaction in these astrophysical phenomena.