Tunable morphologies of ZnO films via the solution precursor plasma spray process for improved photocatalytic degradation performance

The Solution Precursor Plasma Spray (SPPS) process is a novel, versatile and one-step route for building photocatalytic films. Herein, the influence of the precursor solution composition on the microstructure and on the properties of ZnO films prepared via the SPPS process was studied. Nanostructured ZnO particles (i.e. nanorods (NRs) and nanowires (NWs)) were obtained by using a solution of pure Zn(OAc)(2) rather than pure Zn(NO3)(2). Upon adding urea to the Zn(NO3)(2) solution, NRs structured ZnO films were formed as well. The addition of acetic acid into the Zn(OAc)(2) solution led to a damage of the nanostructured morphologies likely due to the inhibition of the zinc-containing clusters formation. UV-visible analyses demonstrate that all samples exhibit narrower bandgaps than pure ZnO. The A02 and NO3 samples prepared from Zn(OAc)(2) and Zn(NO3)(2) solutions, respectively, exhibit photodegradation efficiency up to 100% under UV light irradiation. Moreover, A02 and NO3 samples were able to bleach 46.2% and 54.6% of the Orange II dye under visible light, respectively. Trapping experiments revealed that hydroxyl radicals ((OH)-O-center dot), holes (h(+)) and electrons (e(-)) play a key role in the photodegradation of Orange II. This study highlights the versatility of the SPPS process and demonstrates that the final nanostructured morphologies of ZnO can easily be controlled by adjusting the precursor solution composition. This result further revealed the potential strategy for optimizing the microstructure and photocatalytic performances of other metal oxide films.