Apart from active metals, supports also contribute significantly to the catalytic performance of supported metal catalysts. On account of the formed strain and defects, the heterostructured surface of the support may play a crucial role to activate the reactant molecules, while it is usually neglected. In this work, the Pt/γ-Mo2N catalyst was prepared via a facile solution method. This Pt/γ-Mo2N catalyst showed excellent activity and stability for catalyzing the water–gas shift (WGS) reaction. The reaction rates at 240 °C were 16.5 molCO molPt –1s–1 in product-free gas and 5.36 molCO molPt –1 s–1 in full reformate gas, which were almost 20 times that of the catalysts reported. It is found that the molybdenum species in the surface of the Pt/γ-Mo2N catalyst is molybdenum oxide as MoO3. This surface MoO3 is very easily reduced even at room temperature, and it transformed into highly distorted MoO x (2 < x < 3) in the WGS reaction. The MoO x on the catalyst surface greatly enhanced the capability of generating active oxygen vacancies to dissociate H2O molecules, which induced unexpectedly superior catalytic performance. Therefore, the intrinsically active surface in the Pt/γ-Mo2N catalyst for the WGS reaction was molybdenum oxide as MoO x (2 < x < 3).

In heterogeneous catalysis, the interface between active metal and support plays a key role in catalyzing various reactions. Specially, the synergistic effect between active metals and oxygen vacancies on support can greatly promote catalytic efficiency. However, the construction of high-density metal-vacancy synergistic sites on catalyst surface is very challenging. In this work, isolated Pt atoms are first deposited onto a very thin-layer of MoO3 surface stabilized on γ-Mo2N. Subsequently, the Pt–MoOx/γ-Mo2N catalyst, containing abundant Pt cluster-oxygen vacancy (Ptn–Ov) sites, is in situ constructed. This catalyst exhibits an unmatched activity and excellent stability in the reverse water-gas shift (RWGS) reaction at low temperature (300 °C). Systematic in situ characterizations illustrate that the MoO3 structure on the γ-Mo2N surface can be easily reduced into MoOx (2 < x < 3), followed by the creation of sufficient oxygen vacancies. The Pt atoms are bonded with oxygen atoms of MoOx, and stable Pt clusters are formed. These high-density Ptn–Ov active sites greatly promote the catalytic activity. This strategy of constructing metal-vacancy synergistic sites provides valuable insights for developing efficient supported catalysts.

The metal-support interfaces between metals and oxide supports have long been studied in catalytic applications, thanks to their significance in structural stability and efficient catalytic activity. The metal-rare earth oxide interface is particularly interesting because these early transition cations have high electrophilicity, and therefore good binding strength with Lewis basic molecules, such as H2O. Based on this feature, here we design a highly efficient composite Ni-Y2O3 catalyst, which forms abundant active Ni-NiOx-Y2O3 interfaces under the water-gas shift (WGS) reaction condition, achieving 140.6 μmolCO gcat−1 s−1 rate at 300 °C, which is the highest activity for Ni-based catalysts. A combination of theory and ex/in situ experimental study suggests that Y2O3 helps H2O dissociation at the Ni-NiOx-Y2O3 interfaces, promoting this rate limiting step in the WGS reaction. Construction of such new interfacial structure for molecules activation holds great promise in many catalytic systems.

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The reaction of aldehydes with ethylenediamine for the preparation of 2-imidazolines has been studied using hydrogen peroxide as an oxidant in the presence of sodium iodide and anhydrous magnesium sulfate. A mild, green, and efficient method is established to carry out this reaction in high yield.