Synthesis of Zr-Doped BaTaO2N Platelets from a TaC Precursor for Efficient Photocatalytic H2 Production

Two-dimensional (2D) perovskite-type oxynitrides are highly attractive for photocatalytic solar-to-chemical conversion, yet conventional molten-salt synthesis is severely challenged by sensitive binary flux controls and dense structural defects. Herein, we developed a streamlined, single-component potassium chloride (KCl) molten-salt-assisted thermal nitridation strategy utilizing an innovative tantalum carbide (TaC) and barium hydroxide (Ba(OH)2) precursor combination to direct the growth of well-defined, single-crystalline 2D barium tantalum oxynitride (BaTaO2N) platelets. Concurrently, atomistic Zr4+ substitution efficiently alleviates detrimental Ta3+ defects and elevates the conduction band potential to amplify the thermodynamic driving force for proton reduction. When decorated with platinum@chromium oxide (Pt@Cr2O3) core–shell structured cocatalysts, the optimized Zr-doped BaTaO2N platelets register a maximum initial average H2 evolution rate of 305 μmol h–1 and an apparent quantum yield (AQY) of about 3.24% at 450 nm under mild sacrificial conditions. Furthermore, femtosecond transient absorption spectroscopy verifies that this continuous core–shell architecture delivers the highest sub-nanosecond electron extraction efficiency among all configurations. Overall, this work provides a robust synthesis strategy for preparing highly crystalline 2D Ta-based oxynitride platelets and optimizes their interfacial carrier management for efficient solar hydrogen production.