Abstract <p>Photocatalysts are applied for the oxidative decomposition of pollutants as well as hazardous substances under aerobic conditions, which is a downhill reaction (i.e., ∆<i>G</i>° &lt; 0). In such reactions, we have reported that a p-type semiconductor surface within an organic p–n bilayer can catalyze the same oxidation reaction not only under light illumination but also in the dark (i.e., so-called dual-functional catalysis), where distinct oxidizing powers, which arise at the top of the valence band and bottom of the conduction band, respectively, are available for oxidation. In particular, the oxidation of hydrazine (N₂H₄) to nitrogen (N₂) is kinetically unfavorable because of the four-electron transfer reaction; thus, the addition of a co-catalyst is required to achieve a dual catalysis reaction for N₂H₄ oxidation, especially in the dark. In this study, an organo-bilayer comprising a perylene derivative (PTCBI, n-type) and iron phthalocyanine (FePc, p-type) exhibited dual catalytic activity for N₂H₄ oxidation without loading a co-catalyst. This is a novel and advanced example that cannot be achieved using previous systems. Based on dual catalysis, the organo-bilayer successfully induced a combustion reaction under bias-free conditions, where N₂H₄ oxidation occurred along with the reduction of O₂. Furthermore, this study also demonstrated that titanium oxide (TiO₂), one of the most conventional and efficient photocatalysts, cannot exhibit dual catalytic activity for N₂H₄ oxidation, indicating that combustion does not occur in the dark.</p> Graphical abstract <p></p>