Semiconductor properties and redox responses at a-C:N thin film electrochemical electrodes

摘要

The semiconductor capacitances of the nitrogen-doped amorphous carbon (a-C:N) materials with different sp~3/sp~2 C ratios were studied as a function of electrode potential in a-C:N/aqueous electrolyte systems. This dependence of capacitance on electrode potential in aqueous 0.1 M NaOH shows that the investigated a-C:N materials are intrinsic semiconductors. The space-charge layers inside the a-C:N electrodes behave similar to a Helmholtz layer because of the presence of surface states when the electrolytes contain O_2 or anions other than OH~-. The lower density and mobility of carriers of materials with a higher sp~3 C fraction within the a-C: N material causes a suppression of redox reactions, and the lower density of carriers contributes to a lower capacitance.