471173 Semiconducting Perovskite Oxides (ABO3: A = La; B = Cr, Mn, Fe) for Photocatalytic Reduction of CO2
Perovskite oxides of the form (ABO3) is a unique material having a broad range of band gaps. They are mostly prevalent in cubic forms and suited for a vast range of applications from photocatalysis, electrocatalysis, photovoltaics, sensors etc. They are stable in varied conditions and exhibit high oxygen mobility. Usually they have a Group II element like calcium, strontium, barium or lanthanides as the “A” site component while they have transition elements as the “B” site component. These materials can accommodate different elements in their “A” and “B” sites and can form mixed metal oxide phases like A1(1-x)A2xBO3, AB1(1-y)B2yO3 and A1(1‑x)A2xB1(1‑y)B2yO3. Thus, it presents a huge opportunity to control the material properties by simply compositional tuning.
We hereby, investigated the effect of varying the “B” site elements on the band gap and band edge positions. The different “B1” and “B2” elements in AB1(1-y)B2yO3 were chromium, manganese and iron in different compositions while the “A” site had been fixed for lanthanum. We synthesized the materials via Pechini process and characterized through x-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS). These materials were henceforth, tested for photocatalytic CO2 conversion using our lab-built reactor set-up. LEDs of different wavelengths were used to test the photo-reduction effect under visible and UV light. For better understanding of the reaction mechanism, we performed Diffuse Reflectance Infra-red Fourier Transform Spectroscopy (DRIFTS) experiments of CO2 photo-reduction under different light sources. Theoretical calculations based on density functional theory (DFT) have been performed as well to probe the band-structure of these perovskite oxides. Results have been compared for various functionals like LDA, PBE-GGA, B3LYP, HSE06. The effect of composition on band gap tuning of LaB1(1‑y)B2yO3 perovskite oxides and its implications towards photocatalytic reduction of CO2 are thus being explored.
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