Mechanistic study of HER and OER catalyzing performance of Ca incorporated KMgO3 perovskite: A computational approach

This study investigates the potential for improving the efficiency of hydrogen production via photocatalytic water-splitting by examining the effects of Ca substitution in ultra-wide bandgap KMgO3 perovskite. We used density functional theory to conduct a comprehensive comparative theoretical study of structural, electronic, optical, mechanical, and photocatalytic properties of KMg1−xCaxO3(x=0,0.25,0.50,0.75,1). With increasing Ca concentration, the bandgap gradually decreased from 6.56 eV to 5.31 eV, indicating an ultra-wide bandgap. The reason for this trend was revealed through analysis of the total density of states and elemental partial density of states. Ca inclusion increases thermodynamic stability, as evidenced by the negative formation energy values (x=0(-1.528 eV), x=0.25(-259.601 eV), x=0.5(-243.063 eV), x=0.75(-235.106 eV) and x=1(-222.864 eV)). To explore optical transitions, real and imaginary components of dielectric function are analyzed. These materials' high static values (dielectric constant) make them suitable for optoelectronic applications. All compositions have a dual absorption range (both visible and ultraviolet) while KMg0.75Ca0.25O3 reveal the highest absorption coefficient (α). Remarkable α approaching 105cm−1 in the visible range with the maximum value in the UV region for mixed perovskites (x = 0.25, 0.5, 0.75). Make them an appropriate candidate for harvesting light energy. These compounds exhibit favorable mechanical properties and are elastically anisotropic, which makes them highly desirable for photocatalysis. Further, results showed suitable band edge positions for redox reactions. The photocatalytic activity of the doped materials significantly improved in the visible and ultraviolet irradiation range, which is an essential requirement for photocatalytic energy harvesting. The results support the potential implementation of Ca-incorporated KMgO3 perovskites as they offer the possibility of higher output as energy harvesting materials for HER and OER applications.