Catalytic activity of γ-AlO(110) in the NO + H reaction: a DFT study

In this work, the interaction of the surface of γ-Al 2 O 3 (110) with NO and H 2 was studied using density functional theory calculations. Free γ-Al 2 O 3 (110) adsorbs NO and binds H atoms, but repels the H 2 molecule. A triplet of low-coordinated O II -Al III -O II atoms provides the catalytic activity of γ-Al 2 O 3 (110) along the path: (i) the adsorption of NO/Al III is followed by the binding of H 2 to form a hydroxylamine derivative NHOH through an intermediate NO/Al III + 2 × H/O II complex; (ii) recombination of NHOH with the release of N 2 through an intermediate NHOH/Al III + NHOH/Al IV or adsorption of NO followed by the release of N 2 O through the intermediate NHOH/Al III + NO/Al IV ; the pathway ends with the regeneration of γ-Al 2 O 3 (110). The calculated adsorption heats ensure the diffusion of H atoms from the deposited Pt to the surface (110), initiating the formation of the NH 2 /Al III + H/O II complex, which releases NH 3 endothermically and is stable enough to inhibit stage (ii) of the above reaction pathway. An excess of O 2 in the NO + H 2 mixture excludes H/Pt and eliminates inhibition. The formation of oxynitrides is suppressed, but not excluded by more exothermic surface processes. The N-doped conductivity of bulk and surface oxynitrides Al 32 O 47 N and the dependence of the heat of adsorption of H atoms on the band gap width were revealed, which suggests a relationship between the band gap width and catalytic activity. A triplet of O II -Al III -O II atoms provides the catalytic action of the surface of γ-Al 2 O 3 (110). The N-doped conductivity of Al 32 O 47 N oxynitrides, adsorbed states and intermediates suggests a relationship between the band gap and catalytic activity.