A Heterostructure Photoelectrode Based on Two-Dimensional Covalent Organic Framework Film Decorated TiO(2) Nanotube Arrays for Enhanced Photoelectrochemical Hydrogen Generation

The well-defined heterostructure of the photocathode is desirable for photoelectrochemically producing hydrogen from aqueous solutions. Herein, enhanced heterostructures were fabricated based on typical stable covalent organic framework (TpPa-1) films and TiO(2) nanotube arrays (NTAs) as a proof-of-concept model to tune the photoelectrochemical (PEC) hydrogen generation by tailoring the photoelectrode microstructure and interfacial charge transport. Ultrathin TpPa-1 films were uniformly grown on the surface of TiO(2) NTAs via a solvothermal condensation of building blocks by tuning the monomer concentration. The Pt(1)@TpPa-1/TiO(2)-NTAs photoelectrode with single-atom Pt(1) as a co-catalyst demonstrated improved visible-light response, enhanced photoconductance, lower onset potential, and decreased Tafel slope value for hydrogen evolution. The hydrogen evolution rate of the Pt(1)@TpPa-1/TiO(2)-NTAs photoelectrode was five times that of Pt(1)@TpPa-1 under AM 1.5 simulated sunlight irradiation and the bias voltage of 0 V. A lower overpotential was recorded as 77 mV@10 mA cm(−2) and a higher photocurrent density as 1.63 mA cm(−2). The hydrogen evolution performance of Pt(1)@TpPa-1/TiO(2)-NTAs photoelectrodes may benefit from the well-matched band structures, effective charge separation, lower interfacial resistance, abundant interfacial microstructural sites, and surficial hydrophilicity. This work may raise a promising way to design an efficient PEC system for hydrogen evolution by tuning well-defined heterojunctions and interfacial microstructures.