In contrast, the Co (II) complex displays both positive and negative band energy differences, with values of 0.407 eV, 0.379 eV, and -0.409 eV. The presence of positive values suggests that the complex may have higher energy barriers for electron excitation, potentially reducing its overall efficiency in HER. Although the negative band energy difference (-0.409 eV) indicates some favorable electronic interactions, the mixed nature of the band energy differences suggests less consistent catalytic performance compared to the Nickel(II) complex.