XPS Study of Copper-Doped Carbon Aerogels

Copper-doped carbon aerogels were investigated by X-ray photoelectron spectroscopy to determine the chemical nature and distribution of the copper species in the aerogel framework. The Cu2p spectra of both the organic and carbon aerogels show a fairly uniform distribution of copper species in the aerogel network, with a slight increase in copper content going from the edge to the center of the monolith. The O1s spectra of the copper-doped organic aerogel indicate that both the carboxyl and hydroxyl groups of the aerogel framework are involved in chelation of the copper ions. After carbonization, the content of the copper detected by XPS decreases significantly as the copper ions are reduced into metallic copper nanoparticles. These nanoparticles are difficult to detect by XPS because they are coated by a thin carbon layer and migrate into the carbon matrix. The carbon skeleton of the copper-doped carbon aerogels is mainly composed of a uniform micro-graphite-like crystalline network, and no copper−carbon bonds were detectable in the aerogel.