Cobalt ion redox and conductive polymers boosted the photocatalytic activity of the graphite carbon nitride–Co3O4 Z-scheme heterostructure

Abstract

The enhanced photocatalytic hydrogen evolution performance of g-C₃N₄–Co₃O₄ 2D–1D Z-scheme heterojunctions was achieved by employing the cobalt ion redox and conductive polymers (polyaniline, PANi) for the first time. Specifically, a Co₃O₄ 1D nanobelt acting as the Z-scheme heterostructure component could promote the separation of photo-excited charge carriers and increased the redox capacity, and the conductive PANi brought about the boosted transport efficiency of the charge carriers. Notably, cobalt ions were adopted as the intermediate of the electron transfer between two components for boosting the carrier transport and utilization efficiency. Consequently, the Co₃O₄ nanobelt, PANi and cobalt ions exhibited a synergistic effect on facilitating the photocatalytic HER performance of the g-C₃N₄-based heterostructure, and the optimal ternary heterostructure (g-C₃N₄–PANi–Co₃O₄) exhibited a photocatalytic H₂-evolution rate of 4.61 μmol h⁻¹ under visible light, which further increased to 9.95 μmol h⁻¹ by adding Co²⁺ solution owing to the further facilitated transport of charge carriers through the redox reaction of cobalt ions. Moreover, even in the absence of sacrificial agents, this Z-scheme system exhibited a photocatalytic hydrogen production activity of 3.35 μmol h⁻¹ in the Co²⁺ aqueous solution under UV-visible light.