Highly Active and Robust Nanoporous Gold for CO Oxidation: Widening Temperature Window with an Au‐Cu‐Ag Ternary System

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Abstract
Nanoporous gold (npAu) has garnered significant attention as a highly active and selective oxidation catalyst, particularly at low temperatures. While most studies have focused on npAu derived from AuAg alloys, the incorporation of other less noble metals (LNMs), such as Cu, was shown to be a viable opportunity for tuning and enhancing its catalytic properties. The interplay between multiple LNMs present at the same time remains underexplored though. While trimetallic systems like npAu(CuAg) offer the chance for broadening the catalytic scope of npAu even further, a key challenge in utilizing them lies in understanding whether synergistic interactions or a combination of effects exerted by the individual LNMs determine their catalytic performance. To address this, we developed a reliable and reproducible method for synthesizing npAu(CuAg) and compared the trimetallic catalysts to their bimetallic counterparts npAu(Ag) and npAu(Cu) with respect to their catalytic activity for aerobic CO oxidation. Using controlled dealloying, we synthesized npAu(CuAg) with ∼20 nm ligaments, exhibiting an Ag‐rich surface, and a Cu‐enriched bulk. These trimetallic catalysts showed high conversion over a broad temperature regime ranging from room temerature to 250 °C. Electron microscopy and X‐ray photoelectron spectroscopy revealed that during activation under reaction conditions Cu segregates to the surface at elevated temperatures so that finally Ag as well as Cu sites are available enabling the activation of oxygen – on the former at low temperatures and on the latter in the high temperature region >120 °C. In this way, an overall temperature window for catalytic activity is achieved which encompasses the range of npAu(Ag) as well as that of npAu(Cu). At the same time, the thermal stability of the nanoporous network is improved, demonstrating in essence that the ternary alloy outperforms the binary systems by unifying catalytically relevant features of both LNMs.
Funding Information
  • Deutsche Forschungsgemeinschaft (BA1710/29–2)
  • Deutsche Forschungsgemeinschaft (RO2057/12–2)
  • Deutscher Akademischer Austauschdienst (91680872)

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