Constructing an Electron Highway: Steering Charge Flow in Organic/Inorganic S‐Scheme Heterojunctions for Efficient Solar‐Driven Photocatalytic Hydrogen Production

ABSTRACT Developing low‐cost and highly efficient S‐scheme heterojunction photocatalysts is still a significant challenge towards enhancing the activity of photocatalytic hydrogen evolution (PHE). This study created an S‐scheme heterojunction by in situ growing inorganic Al‐doped SrTiO 3 (ASTO), which possesses superior oxidation capability, on a substrate of the covalent organic framework (TpPa‐1‐COF), which has great reduction capacity, using a solvothermal method. With the advantages of stronger redox capacity, quicker electron transport, and more potent carrier separation, the optimal 5% ASTO/TpPa‐1 S‐scheme heterojunction achieved remarkable photocatalytic performance in ascorbic acid (AsA) solution when exposed to simulated solar light, with a hydrogen production rate of 4.12 mmol g −1 h −1 , which is 14.2 and 11.4 times higher than that of pure TpPa‐1 and ASTO, respectively. This performance outperforms most recently reported SrTiO 3 ‐based and TpPa‐1‐COF‐based heterojunctions under similar conditions. Notably, an intense interfacial internal electric field (IEF) in ASTO/TpPa‐1 heterojunction was formed resulting from the free electron consumption in TpPa‐1 and accumulation in ASTO, which could speed up the transfer dynamics of photoinduced electrons from the conduction band (CB) of ASTO to the valence band (VB) of TpPa‐1 via an interfacial electron‐transfer channel that follows the directed S‐scheme migration process. Moreover, the direction of the IEF is from TpPa‐1 to ASTO, which could accelerate charge separation and migration, thereby prolonging the lifetimes of charge carriers. The dynamic behavior of photoinduced carriers was confirmed by femtosecond transient absorption spectroscopy (fs‐TAS). Overall, this study provides valuable guidance for the rational design of an innovative organic/inorganic hybrid S‐scheme heterojunction.