Rational construction of Z-scheme Ag₂CrO₄/g-C₃N₄ composites with enhanced visible-light photocatalytic activity

Highlights: • Novel visible-light driven Ag₂CrO₄/g-C₃N₄ composites were synthesized. • Ag₂CrO₄/g-C₃N₄ exhibited enhanced visible-light photocatalytic activity. • The reasons for the enhanced photocatalytic activity were revealed. - Abstract: Novel visible-light driven Z-scheme Ag₂CrO₄/g-C₃N₄ composites with different contents of Ag₂CrO₄ were fabricated by a facile chemical precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy and photoelectrochemical measurements. Compared with individual g-C₃N₄ and Ag₂CrO₄, the Ag₂CrO₄/g-C₃N₄ composites displayed much larger photocatalytic activities for the photocatalytic degradation of methyl orange (MO) solution at room temperature under visible light irradiation (λ > 420 nm). Importantly, the optimum photodegradation rate constant of the Ag₂CrO₄/g-C₃N₄ composite at a theoretical weight content of 8.0% Ag₂CrO₄ for the photodegradation of MO was 0.0068 min⁻¹, which was 5.7 and 4.3 times higher than that of pure g-C₃N₄ and Ag₂CrO₄, respectively. Such enormous enhancement in photocatalytic performance was predominantly ascribed to the efficient separation and transfer of photogenerated electrons and holes at the Ag₂CrO₄/g-C₃N₄ interface imparted through the Z-scheme electron transfer. Furthermore, radical trap experiments depicted that both the holes and superoxide radical anions were thought to dominate oxidative species of the Ag₂CrO₄/g-C₃N₄ composite for MO degradation under visible light irradiation. Ultimately, a tentative Z-scheme photodegradation mechanism was proposed. This work may be useful for the rational design of new types of Z-scheme photocatalysts and provide some illuminate insights into the Z-scheme transfer mechanism for application in energy conversion and environmental remediation.