Cost-effective large-scale synthesis of oxygen-defective ZnO photocatalyst with superior activities under UV and visible light

Abstract A cost-effective solution method was developed to produce ZnO photocatalyst in large quantity, through the conversion of e-Zn(OH) 2 to ZnO in NaOH solutions. Experimental results indicated that the concentrated NaOH solution (4 mol L −1 ) promoted the rapid formation of ZnO owing to the enhanced dissolution-precipitation reactions. The large-scale synthesis was also achieved with high-yield and solvent-recyclability. Structural analysis based on X-ray photoelectron spectroscopy, electron spin resonance and photoluminescence revealed that the as-prepared ZnO photocatalyst was rich in oxygen vacancies (V O ). The V O -rich ZnO photocatalyst exhibited improved visible-light absorption, higher photocurrent responses and superior activities toward the degradation of rhodamine B under both UV (λ~254 nm) and visible-light illumination (λ>420 nm) compared to commercial ZnO and P25 TiO 2 powders, as well as good cycle stability. Based on the results of photoluminescence and active species detection, the V O -enhanced photocatalytic activity was attributed to the generation of V O -isolated level in the band structure. Under UV light, the V O -level could promote charge separation by trapping the photoinduced electrons, while under visible-light, the V O -level improved visible-light absorption and facilitated the charge generation. The presently developed synthesis may potentially benefit the large-scale production and low-cost application of ZnO photocatalyst for solar energy utilization.