In contrast, the Co (II) complex exhibits a mix of positive and negative band energy differences (0.407 eV, 0.379 eV, and -0.409 eV). Positive band energy differences indicate a higher energy gap for electron transfer, which can act as a bottleneck, reducing electron mobility. The mixed nature of the energy differences suggests localized electron traps or discontinuities in the electronic pathways, leading to lower overall electron mobility. This inconsistency can hinder the effective transport of electrons to the catalytic sites, thereby reducing the efficiency of HER.