This research presents a new series of tetrabenzoporphyrins (TBPs) bearing p-diphenylaminophenylethynyl and p-carboxylphenylethynyl groups or two p-carboxylphenylethynyl groups in a trans-fashion on a TBP core for photoelectrochemical O 2 reduction. Impact of electron-donating diphenylamino and electron-withdrawing surface-anchoring carboxyl groups on photophysical and electrochemical properties of the target TBPs was experimentally and theoretically investigated in comparison with those of their benchmark analog. The results show that while the p-carboxylphenylethynyl group give an electronic contribution to the molecules by lowering energy gap, the role of the p-diphenylaminophenylethynyl group is found to be trivial. Preliminary inves-tigation on electrochemical O 2 reduction indicates significant catalytic activities of TBP-modified TiO 2 /fluorene-doped tin oxide electrodes at potentials of À 0.2 V and À 0.3 V vs. normal hydrogen electrode (NHE) in a pH-neutral and ambient aqueous condition, leading to H 2 O 2 formation. Upon photoirradiation, catalytic performance of such TBPbased electrodes is further enhanced with the optimum yield obtained when the dicarboxyl derivatives and the potential of À 0.3 V vs. NHE are applied. Proposed photoinjection mechanism of the dye/TiO 2 simulated by time-dependent density functional theory calculations supported the experimental results indicating the favorable role of the target TBPs as photoelectrocatalysts in the O 2 reduction.