Enhanced Photocatalytic Hydrogen Evolution from Organic Ternary Heterojunction Nanoparticles Featuring a Compact Alloy‐Like Phase

Abstract Organic semiconductor nanoparticles (NPs) are attractive photocatalysts to produce hydrogen from water splitting. Herein, a ternary strategy of incorporating crystalline n‐type molecule IDMIC‐4F into the host system made of p‐type polymer PM6 and n‐type molecule ITCC‐M is demonstrated. ITCC‐M and IDMIC‐4F form compact alloy‐like composite with shorter lattice spacing in the ternary p/n heterojunction NPs, resulting in enhanced exciton dissociation and charge transfer characteristics. As the result, an unprecedented hydrogen evolution rate (HER) of 307 mmol h⁻¹ g⁻¹ and a maximum apparent quantum efficiency of 5.9% at 600 nm are achieved in the optimized ternary NPs (PM6:ITCC‐M:IDMIC‐4F = 1:1.3:0.2), which is among the highest HER from organic photocatalysts to the best of the authors’ knowledge. The alloy‐like composite also improves the operational stability of ternary NP photocatalysts. This study shows that synergizing two compatible n‐type small molecules to form alloy‐like composite is a promising approach to design novel organic photocatalysts for boosting the photocatalytic hydrogen evolution efficiency.