Influence of Cr3+ doping on oxygen evolution reaction kinetics and photoluminescence properties of ZnSnO3 nanoparticles

Cr3+ doped ZnSnO3 nanoparticles (NPs) are synthesized by using Aloe vera mediated solution combustion method and their luminescence and oxygen evolution reaction has been investigated. The Bragg reflections of ZnSnO3:Cr (1-9 mol%) NPs exhibits cubic structure. The addition of the dopant induces the lattice strain and peak shifting towards higher angle is observed. Apart from that no other impurity related peaks were observed. The surface morphology consists irregular sized and shaped agglomerated NPs. The EDAX spectra confirms the purity of the sample. The estimated crystallite size decreases from 33 to 26 nm whereas optical band gap increases from 2.98 to 3.18 eV with increase in dopant concentration. The photoluminescence emission spectra was recorded at excitation wavelength 250 nm shows intense blue emission. Blue emission can be attributed to defect-level emission such as oxygen vacancies and 2E -> 4A(2) transition of Cr3+ ions. The CIE coordinates lies well within the blue region. The average color correlated temperature was found to be 70238 K showing cooler appearance. This might finds an application in residential and commercial lighting, street lighting, stage lighting, fitness trackers and smartwatches etc. Further, Oxygen Evolution Reaction (OER) kinetics were carried out for ZnSnO3:Cr (0, 1, 5 and 9 mol%) NPs. the OER activity which shows the over potential of 269, 263, 256, and 365 mV for the 0, 1, 5, 9 mol% Cr3+ doped ZnSnO3 NPs. The Tafel slope observed for the ZnSnO3:Cr (0, 1, 5, and 9 mol%) samples was found to be 76, 65, 90 and 249 mV/dec, indicating a Volmer-Heyrovsky mechanism. Additionally, chronoamperometry and Electrochemical impedance spectroscopy analysis were carried out. From these findings, ZnSnO3:Cr (1,5 mol%) NPs is an highly efficient electrocatalysts for the oxygen evolution reaction (OER). Thus, the synthesized ZnSnO3:Cr finds an application in the field of display technology and in energy storage devices.