The intensities of the light sources for 385 nm, 515 nm and simulated solar light excitation were 5 mW.cm -2 , 25 mW.cm -2 and 100 mW.cm -2 , respectively. Using 385 nm light, TiO2 performs much better than its plasmonic counterpart. Surprisingly, the Au-TiO2 SPs demonstrate much lower H2O2 generation rates upon excitation by light of individual wavelengths of 385 nm and 515 nm, compared to excitation by light of both wavelengths simultaneously, or when using simulated solar light. Moreover, the H2O2 generation using 385 nm and 515 nm wavelength simultaneously is equivalent to the H2O2 generation using simulated solar light. This underlines that simultaneous excitation by UV and visible light at the plasmon resonance frequency is necessary to trigger the synergistic effect of both exciting the plasmonic Au and creating electron-hole pair formation and separation in TiO2. The lower total irradiance when combining the 385 nm and 515 nm light sources, compared to that of simulated solar light, indicates an expected dominant contribution of excitation at the maximum plasmon resonance wavelength, compared to broadband light intensity from simulated solar light.