Enhanced photo-electrochemical response of screen-printed electrodes based on g-C3N4 hollow spheres and other morphologies for sensing applications

Abstract

In this work, graphite-like carbon nitride (g-C3N4) materials were synthesized with different morphologies including bulk, fibers, sheets and hollow spheres, and their photo-electrocatalytic behaviors compared face-to-face. Thereafter, g-C3N4 materials were deposited on ITO substrates for the development of four photo-electrochemical sensing platforms. A systematic characterization evidenced the shape, surface area, crystal structure, composition, electronic structure, photophysical behavior and electrocatalytic activity contributions on an integral photo-electrochemical response. The voltammetric and amperometric results revealed a higher photo-electrocatalytic activity of the electrodes containing hollow spheres compared to other morphologies, with signals up to three orders of magnitude more intense when H2O2 was used as a molecule probe. Those electrodes also showed current responses up to 20-fold more intense under UV-light irradiation compared to measurements in darkness. The response intensification was attributed to a synergic contribution of i) superior adsorption and diffusion processes on the inner and outer faces of hollow spheres, ii) narrowed bandgap that allows extended absorption to the visible-light range with dramatically enhanced light-harvesting capability, iii) decreased recombination of the photogenerated electron-hole pairs, and iv) the presence of more abundant cyano (CN) functional groups which promotes interactions with small target analytes and catalyze some redox reactions. Thereby, morphology modulation resulted in a crucial strategy for improving the photo-electrochemical response of electrodes containing layered g-C3N4 materials. These results support the development of innovative substrates as signal-transducers for improved sensing applications.