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.