Boosting the photocatalytic hydrogen evolution activity of g-C3N4 nanosheets by Cu2(OH)2CO3-modification and dye-sensitization

Abstract

Considering the cleanness and renewability of the solar H₂-production system, photocatalytic H₂-production from water splitting with the assistance of nonprecious and Earth-abundant cocatalysts has become a research hotspot. Herein, robust Cu₂(OH)₂CO₃ nanoparticles were successfully anchored onto the surface of g-C₃N₄ nanosheets through a mild precipitation route in which Cu₂(OH)₂CO₃ serves as an effectively nonprecious metal-based cocatalyst for boosting hydrogen generation. The results demonstrated that the as-prepared hybrid Cu₂(OH)₂CO₃/g-C₃N₄ nanocomposite photocatalyst with an optimum 3 wt% loading amount of Cu₂(OH)₂CO₃ exhibited a noticeable improvement of photocatalytic H₂-evolution performance under visible light illumination. The boosted H₂-evolution activity was associated with the formation of active Cu species during the photocatalytic process, which could promote the interfacial charge separation and simultaneously reduce the overpotential of hydrogen generation, thus boosting the H₂-evolution activity over the hybrid photocatalyst. More importantly, by introducing an optimum amount of fluorescein dye molecules into the photocatalytic system, the maximum photocatalytic H₂-production rate over the binary Cu₂(OH)₂CO₃/g-C₃N₄ photocatalyst could be further improved to be 22.6 μmol h⁻¹, 19.3 and 3.8 times higher than those of pristine g-C₃N₄ and the corresponding binary catalyst without the assistance of fluorescein. These results could be ascribed to the positively cooperative effects of Cu₂(OH)₂CO₃, fluorescein dye molecules and g-C₃N₄, which lead to the increasing light absorption ability, fast charge mobility and efficient charge separation of the fluorescein-sensitized Cu₂(OH)₂CO₃/g-C₃N₄ hybrid photocatalyst, thus ultimately boosting the photocatalytic H₂-production activity. This study may pave a new way for engineering a low-cost, high-efficiency, noble-metal-free and dye-sensitized cocatalyst/semiconductor system for solar-to-fuel conversion.