Conjugated Polyelectrolytes/Sucrose‐Doped Hydroxyl‐Rich Carbon Nitride Heterojunctions for Photocatalytic Hydrogen Evolution: Morphology Control, Interfacial Modulation, and Energy Band Engineering

Abstract Herein, a novel, ecofriendly and facile strategy have been introduced to fabricate conjugated polyelectrolytes (CPEs)‐assisted hydroxylated CN (CNOH) heterojunctions for enhancing photocatalytic hydrogen evolution (PHE). This work synthesizes CNOH nanosheets utilizing a urea‐sucrose aqueous solution as the precursor. Subsequently, this work incorporates CPEs, including a donor–donor (D–D) cationic conjugated polyelectrolyte (PFNBr) and an anionic donor–acceptor (D–A) CPEs (PCP‐2F‐Li), to respectively exfoliate CNOHx into a folded, porous lamellar nanostructure with dispersed nanofragments on the CNOH nanosheets, where the PFNBr or PCP‐2F‐Li can be uniformly dispersed to form type‐II y%PFN/CNOHx and y%PCP/CNOHx heterojunctions. Optimally, 3%PFN/CNOH0.5 and 1%PCP/CNOH1 heterojunctions (1.5 wt% Pt) respectively demonstrate PHE rates of 22.75 and 24.01 mmol g⁻¹ h⁻¹ under visible‐light irradiation (600 mW cm⁻ 2 ), respectively outperforming that of pristine bulk carbon nitride (BulkCN) by 13.87 and 14.64 times. The remarkable enhancement in PHE performance is attributed to the well‐matched energy levels between CPEs and CNOH, increased specific surface area facilitated by CPEs‐promoted exfoliation, the broadened visible light absorption due to sucrose and CPEs doping, strengthened interfacial interactions by hydrogen bonding and π–π stacking, and improved hydrophilicity conferred by sucrose doping on CNOH. This work presents a novel design strategy for CPEs/CNOH heterojunctions by CPEs‐promoted effect, thus advancing the development of efficient sunlight‐driven chemical reactions.