Simple electrochemical synthesis of black metal oxides for enhanced visible light absorption

• Simple electrochemical method for the hydrogenation of metal oxides in 10 s.
• Water with small amount of fluorine ions is used as electrolyte.
• No microstructural variation during the hydrogenation process.
• Significantly higher absorbance in the visible and IR region of light.
• Safe, low cost and fast process and can be adapted for large scale synthesis.

Hydrogenation of oxides such as TiO2 is so far considered as a time consuming and complex process which requires high temperature annealing in hydrogen atmosphere. In this work, an electrochemical method for the hydrogenation of metal oxides is introduced. The electrochemical hydrogenation process is a low cost process which requires only a few seconds for synthesizing the black semiconducting oxides. Water with small amount (0.2 vol%) of ionic species like fluorine ions is used as electrolyte. The black semiconducting oxides prepared using the electrochemical hydrogenation process exhibit very good absorption of light in visible region.