Straddled Band Aligned CuO/BaTiO3 Heterostructures: Role of Energetics at Nanointerface in Improving Photocatalytic and CO2 Sensing Performance

This work details novel insights on the role of energetics, that is, energy band bending and built-in potential at the nanointerface of CuO/BaTiO3 forming type I p/n heterostructures, evaluated by correlating X-ray photoelectron spectroscopy and ultraviolet diffuse reflectance spectroscopy studies. Cetyltrimethylammonium bromide (CTAB) assisted hydrothermal route was used to synthesize BaTiO3 cuboids with six active {100} facets, and its CuO based heterostructures were tested for bifunctional applications in environmental nanoremediation. Straddled CuO/BaTiO3 heterostructures reported herein showcased exceptional flexibility as a ultraviolet (UV) active photocatalyst for methyl orange (MO) degradation and chemo-resistive CO2 gas sensor. CuO/BaTiO3 heterostructures in equimole ratio could degrade 99% MO in 50 min with rate constant (kappa) of a first-order reaction observed to be 10 samples, respectively. Subsequently, in a parallel application, trials and 100-fold greater in comparison with BaTiO3 and CuO were carried out on CuO/BaTiO3 heterostructures for their sensitivity and stability toward CO2 gas below 5000 ppm. Upon Ag decoration, the sensor response improved compared to CuO/BaTiO3 heterostructures at 160 degrees C, with enhanced response/recovery times (t(90)) of 300 and 320 s, respectively towards 100 ppm CO2 gas. Improved photoactivity was rationalized in terms of effective charge severance of photogenerated e-h pairs owing to favorable band alignment, while the optimum CO2 sensor response was attributed to efficient nanointerfaces configured in large numbers and Ag-0/Ag+ acting as redox couple.