Investigation of Photoelectrocatalytic and Magnetic Properties of Sr 2 YbRu 1- x Ta x O 6 ( x = 0, 0.25, 0.5, 0.75, and 1).

We report the effect of substitution of Ru by Ta in Sr 2 YbRuO 6 on its magnetic and photoelectrocatalytic properties. The powder X-ray diffraction data, was satisfactorily refined in the monoclinic space group, P 2 1 / n . The DC magnetization studies indicated that Sr 2 YbRuO 6 shows antiferromagnetic interaction through Yb-O-Ru orbital ordering, with the highest Weiss temperature, among Sr 2 YbRu 1- x Ta x O 6 ( x = 0, 0.25, 0.5, and 0.75) which have values of -148, -125, -118, and -102 K, respectively. The difference in observed and theoretical magnetic moments was found to increase as x increases. It was also observed that with the increase of Ta concentration in Sr 2 YbRu 1- x Ta x O 6 , the band gap increased almost linearly, from 1.78(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 valence band, 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 density of 17 μA/cm 2 and photoresponse current of 5.5 μA/cm 2 at 0.8 V at an onset potential at 0.29 V vs Ag/AgCl for Sr 2 YbRuO 6 . The XPS analysis showed Ta and Ru to be in +5/+4 oxidation states, with the highest concentration of Ru 4+ ion observed for Sr 2 YbRuO 6 . The presence of oxygen vacancies was confirmed by XPS as well as EPR studies.