Zeta potential is a parameter that can indicate the stability of a disperse system to aggregation of catalyst nanoparticles or sedimentation. It depends on the composition of the dispersed system, pH, electrolytes... If the dispersed system is stable, it will work well as a photocatalytic catalyst. For your disperse system, it is necessary to experimentally determine the zeta potential.
In the field of catalysis, zeta potential is a parameter that decribe the surface charge. The negative zeta potential indicates more electrons in the surface of your catalyst, which maybe favorable for the CO2 adsorption and activation.