Simplistic wet-chemical coalescence of ZnO with Al2O3 and SnO2 for enhanced photocatalytic and electrochemical performance.

A wet-chemical route for the development of Al₂O₃–ZnO and SnO₂–ZnO hierarchical heterostructures (HHSs) was opted to enhance the photocatalytic and electrochemical properties of SnO₂ and Al₂O₃ nanoparticles. Successful coalescence of ZnO hierarchical structure with Al₂O₃ and SnO₂ significantly increased the degradation of Congo red dye under ultraviolet irradiation. More importantly, SnO₂–ZnO HHS exhibited superior photocatalytic activity than Al₂O₃–ZnO which was credited to its improved charge carrier generation and transfer characteristics, revealed using in-depth electrochemical spectroscopy (cyclic voltammetry and electro-chemical impedance spectroscopy). In addition, electrochemical investigation affirmed the photoanodic efficacy of HHSs in polysulfide electrolyte. SnO₂–ZnO HHS exhibited optimal electron–hole generation and transfer characteristics (e.g., ~ 17.5 Ω charge carrier transfer resistance at photoanode/polysulfide electrolyte interface), affirming its suitability for quantum-dot sensitized solar cells. [ABSTRACT FROM AUTHOR]