Electrochemical characterization and photocatalytic activity of MBiO3 (M = K and Na) for hydrogen production

This work reports the hydrogen production of KBiO3 and NaBiO3. The potassium compound was synthesized by chemical substitution while commercial NaBiO3 was used. Both samples were characterized by X-ray diffraction (XRD), scanning electronic microscopic (SEM), UV–vis spectroscopy, voltammetry and chronoamperometry. The XRD patterns suggest that KBiO3 has a cubic crystalline structure while rhombohedral NaBiO3·xH2O was found for the sodium compound. SEM images reveal micron sized particles with octahedral shape for KBiO3 and flower shape for NaBiO3. The band gap was calculated from the diffuse reflectance spectrum resulting in 1.9 eV and 2.6 eV for KBiO3 and NaBiO3, respectively. Moreover, with electrochemical techniques it was possible to estimate the electroactive surface area as well as the recombination constant of the samples. Hydrogen production was performed and monitored on a Shimadzu gas chromatographer under UV and visible light radiation without sacrificial agents. KBiO3 shows a superior photocatalytic efficiency with a hydrogen evolution rate of more than double that obtained by NaBiO3.