The catalytic performance of gold nanoparticles (NPs) can be dramatically changed by choosing support materials and by designing the fine architecture of contact structure between gold NPs and the supports. So far many kinds of base metal oxides including acidic metal oxides such as Nb₂O₅ ^[1], carbon materials, organic polymers have been reported as effective support for gold NPs. Each one of supported gold NPs show unique catalytic activity and selectivity. A typical example is core/shell structured Au/NiO, by which a new chemical plant to produce methylmethacrylate from methacrolein was constructed in 2008. Other examples are AsH₃ gas sensors and mercury collectors for the environmental analyses. Accordingly, a key current issue is stability and life of gold catalysts. Typical examples for long life catalysts are MINTEK catalysts ^[2] and YD-3 Yantai catalysts, the latter is composed of Al₂O₃ modified with a-Fe₂O₃, La₂O₃ and gold NPs ^[3].

Fig. 1

Fig. 1. (a) CO oxidation curves of Au/X-800. Gas flow: 1 v% CO + 1 v% O2 and balanced with He, 33.3 mL min-1, 100 mg catalyst, space velocity (SV) = 20000 mL gcat-1 h-1; (b) The CO conversion curves as a function of reaction time on the Au/TH-800 (10 mg) and TWC of JM888 (5.4 mg) at 400 ℃ with SV of 200 L gcat-1 h-1 and 1100 L gcat-1 h-1, respectively. Reaction gas composition: 1.6 v% CO, 1 v% O2, 0.01 v% propene, 0.0087 v% toluene, 10 v% water and balanced with He. Reproduced with permission from Wiley.

Recently, a team of DICP directed by J. Wang and T. Zhang discovered that Au NPs could interact strongly with hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂, the main component of bones and teeth) support to form the so called Strong Metal-Support Interaction (SMSI) upon high-temperature calcination ^[4]. The SMSI results in the encapsulation of Au NPs which improves their sintering resistance significantly but reduces their activity due to the coverage of the active sites.

Quite recently, the authors have modified the HAP by incorporating TiO₂ into the HAP support ^[5]. Using this support they developed a new type of Au/HAP-TiO₂ catalyst in which the Au NPs were partially covered by a thin layer of the HAP and partially exposed and contacted with TiO₂. By this unique nanoscale architectural design, it was found that this supported Au nanocatalyst not only possessed high activity and good sintering resistance after calcination at 800 ℃ for a variety of reactions but also demonstrated excellent durability that outperforms a commercial TWC (Three Way Catalyst) for CO oxidation under simulated practical conditions.

This work will provide a new avenue for practical applications of supported Au nanocatalysts, especially for high temperature catalytic reactions, thus may facilitate the practical applications or even commercialization of supported Au catalysts.