Constructing a direct Z-scheme La2NiO4/g-C3N4 hybrid photocatalyst with boosted visible light photocatalytic activity

Abstract

Abstract A mediator-free direct Z-scheme La2NiO4/g-C3N4 hybrid photocatalyst was successfully constructed by a facile mixed-calcination route and applied for the photocatalytic degradation of methyl orange (MO) in aqueous solution at room temperature under visible light irradiation (λ > 420 nm). Noticeably, all of the La2NiO4/g-C3N4 hybrids illustrated significantly boosted photocatalytic performances compared to the individual La2NiO4 and g-C3N4. More importantly, the optimal La2NiO4/g-C3N4 hybrid at a theoretical mass fraction of 3.3% La2NiO4 revealed the highest apparent photodegradation rate constant, which was nearly 4.14 and 3.42 times larger than that of pristine La2NiO4 and g-C3N4, respectively. Such a remarkably augmented catalytic activity could be mainly ascribed to the formation of an all-solid-state Z-scheme La2NiO4/g-C3N4 system composed of La2NiO4 and g-C3N4, which not only boosted the separation efficiency of photogenerated electrons and holes but also possessed splendid oxidation and reduction ability for superior photocatalytic activity. Furthermore, the active species trapping experiments demonstrated that holes (h+) and superoxide radicals ( O−2) were the predominant active species in the photocatalytic reaction process. Finally, a tentative Z-scheme photodegradation mechanism responsible for the charge separation was also proposed based on the results of energy band positions, active species trapping experiment and photoluminescence spectroscopy.