Magnetic and Optoelectronic Properties of Cobalt and Iodine Doping in ZnSe Nanowires for Spintronic and Water-Splitting Applications: A First-Principles Investigation

This study employs first-principles calculations to comprehensively investigate the optoelectronic, magnetic, and photocatalytic properties of ZnSe nanowires, with a focus on cobalt (Co) doping and iodine(I) codoping. Our results show that the bandgap of ZnSe nanowires was calculated to be 3.04 eV, which is diameter-dependent, exhibiting a decreasing trend as the nanowire diameter increases. The introduction of Co(II) induces spin polarization, resulting in a magnetic moment of 3 μ_B. The iodine(I) codoping can change the ground state of the Co-doped ZnSe nanowire from AFM to FM due to the exchange coupling between electrons provided by Iodine and Co-d states. Optical analysis shows that Co doping introduces d–d transition bands in the range of 1.6–1.91 eV, while iodine codoping further produces mid-infrared and near-infrared absorption bands, attributed to strong FM coupling. The correlation of the spin–spin coupling and optical behavior revealed that in FM-coupled systems both the d–d transition peaks and the optical bandgap occur at lower energies compared to those in AFM-coupled systems. Additionally, photocatalytic studies reveal that both pure and Co-doped ZnSe nanowires exhibit suitable band alignments for water splitting. Co-Iodine codoped ZnSe nanowires show enhanced water adsorption and superior catalytic performance, achieving a low oxygen evolution reaction (OER) overpotential of 0.55 V. These results highlight the dual functionality of Co-Iodine codoped ZnSe nanowires in spin-based electronic devices and photocatalytic applications, underscoring their versatility for advanced technological applications.