The Incorporation of Carbon Element into Nanoporous Anodic Alumina by Pulse Anodization.

The incorporation of carbon element into nanoporous anodic aluminum oxides from oxalic acid electrolyte was studied. The carbon element content in nanoporous anodic alumina by pulse anodization reaches up to ∼20 at.%, while it remains ∼7 at.% under constant anodization. It was proposed that the ionic dynamics in nanopores governs the carbon-containing anions incorporation into nanoporous anodic oxides. For the same 20 V resting voltage, the content of carbon element remains unchanged in a broad range of working voltages: 40-150 V. X-ray photoelectron analysis further revealed that the sp²/sp³ and C-O/C═O ratios increased significantly as the working voltage increased. The color exhibited by the nanoporous anodic alumina was related to the chemical states of the carbon present in the alumina, and not the carbon content.