Attempts to improve performance of the semiconductor photo-electrodes used either for oxidation or reduction of species present in the electrolyte very often require presence of a catalysts However, identification of new molecular catalysts, active in often highly corrosive media or under unfavourable band energetics is a challenge.  N-type mesoporous tungsten trioxide, WO₃, is one of few stable semiconductor materials able to photo-electrochemically split water under solar light irradiation but it’s operational acidic environment restricts use of any catalyst to the precious metal based oxygen-evolution electrocatalysts.  In an attempt to overcome this limitation, an addition to the acidic electrolyte of Keggin-type polyoxometalates (POMs) species was investigated in function of their electrocatalytic capabilities to drive oxygen evolution. The presence of this catalyst in the electrolyte makes it particularly efficient for use with nanoporous structure allowing deep penetration of the catalyst dissolved in the electrolyte. Moreover, moderate doping with metal cations of WO₃ has been found to enhance visible blue light absorption of tungsten trioxide and, consequently, its photocurrent conversion efficiency. Combination of those two effects allowed achieving of record high water photooxidation currents attained under simulated solar AM 1.5G irradiation. The enhancement of anodic photocurrents will be discussed in the frame of functionalization of different mixed metal oxides with the POMs and correlated with the measurements of the amounts of oxygen evolved at the modified electrodes.