Small Molecule π–π Stacking Promotes Efficient Photoelectrocatalytic Splitting of Aqueous Hydrogen Production from Polyaniline

Abstract Photoelectrocatalysis efficiency depends on light absorption and the effective use of photogenerated carriers but is often limited by inefficient charge transfer and catalytic surface reactivity. In this study, π–π stacking of polar small molecules on aromatic ring‐rich polyaniline (PANI) was carried out to improve its photoelectrocatalytic splitting of water for hydrogen production. Detailed photoelectrochemical experiments and density‐functional theory (DFT) calculations show that small molecules of p‐aminobenzoic acid (PABA) and PANI have the best π–π stacking (compared to p‐toluenesulfonic acid (PTA)), which promotes the separation of carriers on the PANI surface. In addition, the polar effect of the small molecules also improves the reactivity of the PANI surface and also reduces the potential barrier for H2 evolution. The current density of PANI‐PABA reached −0.12 mA/cm2 (1.23 V vs. RHE) 2.53 times higher than that of pure PANI in linear voltammetric scanning tests under light. This strategy of introducing polar small molecules into organocatalysts via π–π stacking will provide new ideas for the preparation of efficient organic photoelectrocatalysis.