Nanoporous gold is a freestanding material that can, for example, be obtained by electrochemically de-alloying a gold-silver alloy. Left is a porous structure which looks fascinating under the microscope and is made of ligaments and voids of several 10 nm in diameter. But not only that, it has a number of interesting properties, among those also a catalytic activity emerging from gold atoms with low coordination.
In the past 20 years there has been a plethora of studies on this material from groups around the globe. I got in contact with the material in the group of Prof. Marcus Bäumer in Bremen, Germany, who had a project on this material and was collaborating with Prof. Friend at Harvard on this topic. Arne Wittstock, who worked as a phd student on the topic, made some significant contributions to the field. (Find his thesis here (in German))
Marcus and Arne also co-edited a book on the topic in 2012.

I supported this project in 2009 with an initial XPS measurement on the material but later continued to study it in more detail as a postdoc in Uppsala together with Prof. Anders Sandell. During a few synchrotron beamtimes I studied the cleaning of np-Au with ozone treatment and also the addition of titanium dioxide to add further function to the material. Both studies were published (see below).
Back in Bremen I supported two studies that dealt with studying the CO oxidation capability in a model vacuum environment and a study that dealt with modifying np-Au with cerium oxide to use it wor the water-gas shift reaction.

In 2013 Marcus Bäumer and several groups in Germany successfully applied for a DFG "Forschergruppe", a collective national research effort working on the study and utilization of nanoporous gold. The Project was called "NAGOCAT" but unfortunately the project's website is no longer available.