The initial step of TC photo-degradation is unlikely to proceed via direct electron transfer. I doubt that the redox potential of TC is known. It would be very hard to measure it.
So, you mean it would be very hard to anticipate the presence of excess holes or positive charges on the valence band of a component of a catalytic composite ( about 1.6 V/NHE) that could potentially oxidize the tetracycline ( unknown ? V/NHE), right?