Quantum chemical simulation of reactions of hydrogen and oxygen with a gold–nickel bimetallic nanocoating

Quantum chemical calculations are performed to determine the heats of hydrogenation for the simplest nanosized Au3–/Ni2+ bimetallic system via three possible reaction pathways. It is shown that the reaction pathway releasing maximum energy is Au3–/Ni2+ + H2 → (Au3H2)–/Ni2+ with a heat of reaction of 43.7 kcal/mol. Quantum chemical methods are also used to calculate the heats of reaction for several reaction pathways between Au3–/Ni2+ and oxygen. It is found that the pathway that releases maximum energy adds one O atom to Au3H2 while the other one combines with nickel, (Au3H2)–/Ni2+ + O₂ → (Au3H2–O)–/(Ni2O)+, with a heat of reaction of 39.0 kcal/mol. The reaction mechanism and energy budget are determined for the elementary steps involved in the production of gold Au3– and water from the oxide (Au3H2–O)–. Based on the calculated results, an explanation is proposed for experimental results on successive exposure of a gold–nickel bimetallic nanocoating to hydrogen and oxygen. Since contact between gold and nickel results in negatively charged gold and positively charged nickel particles, the calculations are performed for negatively and positively charged gold- and nickel-containing particles, respectively.