Investigation of Photoelectrocatalytic and Magnetic Properties of Sr₂YbRu_1-x Ta _x O₆ (x=0, 0.25, 0.5, 0.75, and 1)

We have synthesized Sr2YbRu1-x Ta x O6 (x = 0, 0.25, 0.5, 0.75, and 1) by solid-statereaction andinvestigated the structural, magnetic, and photoelectrocatalytic propertieson substitution of Ta in place of Ru in Sr2YbRuO6. Structural analysis was performed by Rietveld refinement on X-raydiffraction data. We have performed field-cooled direct current (dc)magnetic susceptibility studies at 1000 Oe and studied the isothermalmagnetization studies at 5 K. From the diffuse reflectance spectroscopyand Mott-Schottky plot, the positions of the valence band andconduction band were obtained. Photoelectrocatalytic studies for oxygenevolution reaction were investigated. The presence of oxygen vacancieswas confirmed by XPS and EPR studies. Wereport the effect of substitution of Ru by Ta in Sr2YbRuO6 on its magnetic and photoelectrocatalytic properties.The powder X-ray diffraction data, was satisfactorily refined in themonoclinic space group, P2(1)/n. The DC magnetization studies indicated that Sr2YbRuO6 shows antiferromagnetic interaction through Yb-O-Ruorbital ordering, with the highest Weiss temperature, among Sr2YbRu1-x Ta x O6 (x = 0, 0.25, 0.5, and 0.75)which have values of -148, -125, -118, and -102K, respectively. The difference in observed and theoretical magneticmoments was found to increase as x increases. Itwas also observed that with the increase of Ta concentration in Sr2YbRu1-x Ta x O6, the band gap increased almost linearly, from1.78(1) eV (x = 0) to 2.08(1) (x = 0.75), and thereafter a sharp increase 2.65(1) eV (x = 1) was observed, with the lowering of energy level of valenceband, along with disruption in orbital ordering as x increases. The photoelectrocatalytic oxygen evolution reaction (OER)studies carried out on the series yield a maximum photocurrent densityof 17 mu A/cm(2) and photoresponse current of 5.5 mu A/cm(2) at 0.8 V at an onset potential at 0.29 V vs Ag/AgCl for Sr2YbRuO6. The XPS analysis showed Ta and Ru to bein +5/+4 oxidation states, with the highest concentration of Ru4+ ion observed for Sr2YbRuO6. The presenceof oxygen vacancies was confirmed by XPS as well as EPR studies.