Nitrogen Incorporated Photoactive Brownmillerite Ca2Fe2O5 for Energy and Environmental Applications

Durga Sankar Vavilapalli; Soma Banik; Raja Gopal Peri; Muthuraaman B; Muralidhar Miryala; Masato Murakami; Klimkowicz Alicja; Asokan K; Ramachandra Rao M S; Shubra Singh

doi:10.1038/s41598-020-59454-w

Nitrogen Incorporated Photoactive Brownmillerite Ca₂Fe₂O₅ for Energy and Environmental Applications

Sci Rep. 2020 Feb 17;10(1):2713. doi: 10.1038/s41598-020-59454-w.

Authors

Affiliations

¹ Crystal Growth Centre, Anna University, Chennai, 600025, India.
² Synchrotron Utilization Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013, India.
³ Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400094, India.
⁴ Department of Energy, University of Madras, Chennai, 600025, India.
⁵ Graduate School of Science and Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo, 135-8548, Japan.
⁶ Materials Science Division, Inter University Accelerator Centre, New Delhi, 110067, India.
⁷ Nano Functional Materials Technology Centre, Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India.
⁸ Crystal Growth Centre, Anna University, Chennai, 600025, India. shubra6@gmail.com.

Abstract

Ca₂Fe₂O₅ (CFO) is a potentially viable material for alternate energy applications. Incorporation of nitrogen in Ca₂Fe₂O₅ (CFO-N) lattice modifies the optical and electronic properties to its advantage. Here, the electronic band structures of CFO and CFO-N were probed using Ultraviolet photoelectron spectroscopy (UPS) and UV-Visible spectroscopy. The optical bandgap of CFO reduces from 2.21 eV to 2.07 eV on post N incorporation along with a clear shift in the valence band of CFO indicating the occupation of N 2p levels over O 2p in the valence band. Similar effect is also observed in the bandgap of CFO, which is tailored upto 1.43 eV by N⁺ ion implantation. The theoretical bandgaps of CFO and CFO-N were also determined by using the Density functional theory (DFT) calculations. The photoactivity of these CFO and CFO-N was explored by organic effluent degradation under sunlight. The feasibility of utilizing CFO and CFO-N samples for energy storage applications were also investigated through specific capacitance measurements. The specific capacitance of CFO is found to increase to 224.67 Fg^-1 upon N incorporation. CFO-N is thus found to exhibit superior optical, catalytic as well as supercapacitor properties over CFO expanding the scope of brownmillerites in energy and environmental applications.