First principles investigation of the titanium/chalcogen doping and codoping in SrZrO3 perovskite structures for enhanced H2 production and CO2 reduction

Abstract

This research investigation utilized DFT computations using the WIEN2k code with the mBJ potential to explore the optoelectronic and photocatalytic properties of lead-free strontium zirconate (SrZrO 3 ). SrZrO 3 has photocatalytic (PC) potential, but its wide band gap limits absorption in the visible light region. To address this limitation, Ti and chalcogen (S, Se, Te) mono- and co-doping were used to modify the electronic structure and improve light-harvesting capabilities. The structural stability of the materials analyzed was confirmed by their negative formation energies, which ranged from −3.77 to −2.77 eV/atom, indicating thermodynamic stability. Pure SrZrO 3 has an indirect band gap of 4.456 eV. Chalcogen (S, Se, and Te) mono-doping and chalcogen/Ti co-doping cause the band gap to shift from indirect to direct, resulting in a significant reduction. The calculated band gaps decrease to 3.634, 2.872, and 2.086 eV for S-, Se-, and Te-doped SrZrO 3 , respectively, and are further reduced to 2.721, 2.285, and 1.177 eV for the corresponding S/Ti, Se/Ti, and Te/Ti codoped systems. These electronic tuning boosts light absorption across the visible-UV spectrum and improves charge transport, making doped and co-doped materials promising for optoelectronic and renewable energy technologies. In the photocatalytic analysis at pH 0, the band-edge positions of SrZrO 3 are notably altered by chalcogen mono-doping and chalcogen/Ti co-doping. The pure SrZrO 3 has a CBM of −1.73 eV and a VBM of 2.73 eV. Doping with S, Se, and Te shifts the CBM to −1.34, −0.97, and −0.58 eV, with VBM at 2.29, 1.90, and 1.5 eV, respectively. In the case of S/Ti, Se/Ti, and Te/Ti co-doping, the CBM/VBM values are −0.89/1.83, −0.68/1.6, and −0.13/1.04 eV, respectively. All investigated compounds thermodynamically support water splitting across various pH levels due to favorable band-edge alignment. They also exhibit suitable band-edge positions for CO 2 reduction pathways, highlighting their multifunctional nature. However, the Te/Ti co-doped system has less favorable band-edge alignment compared to other modified materials. These results demonstrate that the doped and co-doped SrZrO 3 perovskite oxides are thermodynamically feasible multifunctional materials with promising potential for photocatalytic applications.