Polar Aromatic Two‐dimensional Dion‐Jacobson Halide Perovskites for Efficient Photocatalytic H2 Evolution

Abstract Polar materials with spontaneous polarization ( P s ) have emerged as highly promising photocatalysts for efficient photocatalytic H 2 evolution owing to the P s ‐enhanced photogenerated carrier separation. However, traditional inorganic polar materials often suffer from limitations such as wide band gaps and poor carrier transport, which hinders their photocatalytic H 2 evolution efficiency. Here, we rationally synthesized a series of isostructural two‐dimensional (2D) aromatic Dion–Jacobson (DJ) perovskites, namely (2‐(2‐Aminoethyl)pyridinium)PbI 4 (2‐APDPI), (3‐(2‐Aminoethyl)pyridinium)PbI 4 (3‐APDPI), and (4‐(2‐Aminoethyl)pyridinium)PbI 4 (4‐APDPI), where 2‐APDPI and 4‐APDPI crystalize in polar space groups with piezoelectric constants ( d 33 ) of approximately 40 pm V −1 and 3‐APDPI adopts a centrosymmetric structure. Strikingly, owing to the P s ‐facilitated separation of photogenerated carriers, polar 2‐APDPI and 4‐APDPI exhibit a 3.9‐ and 2.8‐fold increase, respectively, in photocatalytic H 2 evolution compared to the centrosymmetric 3‐APDPI. As a pioneering study, this work provides an efficient approach for exploring new polar photocatalysts and highlights their potential in promoting photocatalytic H 2 evolution.