A comprehensive experimental and theoretical study of the CO + NO reaction catalyzed by Au/Ni nanoparticles

The catalytic and structural properties of five different nanoparticle catalysts with varying Au/Ni composition were studied by six different methods, including in situ XAS and DFT calculations. The as-prepared materials contained substantial amounts of residual capping agent arising from the commonly used synthetic procedure. Thorough removal of this material by oxidation was essential for the acquisition of valid catalytic data. All catalysts were highly selective towards N2 formation, with 50-50 Au:Ni material best of all. In situ XANES showed that although Au acted to moderate the oxidation state of Ni, there was no clear correlation between catalytic activity and nickel oxidation state. However, in situ EXAFS showed a good correlation between Au-Ni coordination number—highest for Ni50Au50—and catalytic activity. Importantly, these measurements also demonstrated substantial and reversible Au/Ni intermixing as a function of temperature between 550 °C (reaction temperature) and 150 °C, underlining the i...