Photocatalytic hydrogen peroxide (H2O2) generation represents a promising approach for artificial photosynthesis. However, the sluggish half-reaction of water oxidation significantly limits the efficiency of H2O2 generation. Here, a benzylamine oxidation with more favorable thermodynamics is employed as the half-reaction to couple with H2O2 generation in water by using defective zirconium trisulfide (ZrS3) nanobelts as a photocatalyst. The ZrS3 nanobelts with disulfide (S22−) and sulfide anion (S2−) vacancies exhibit an excellent photocatalytic performance for H2O2 generation and simultaneous oxidation of benzylamine to benzonitrile with a high selectivity of 99%. More importantly, the S22− and S2− vacancies can be separately introduced into ZrS3 nanobelts in a controlled manner. The S22− vacancies are further revealed to facilitate the separation of photogenerated charge carriers. The S2− vacancies can significantly improve the electron conduction, hole extraction, and kinetics of benzylamine oxidation. As a result, the use of defective ZrS3 nanobelts yields a high production rate of 78.1 ± 1.5 and 32.0 ± 1.2 μmol h−1 for H2O2 and benzonitrile, respectively, under a simulated sunlight irradiation.

Here, ZrS3 NBs with both S22− and S2− vacancies are employed to enhance the photocatalytic production of H2O2 coupled with the selective oxidation of benzylamine to benzonitrile in water. The impacts of S22− and S2− vacancies on modulating the charge carrier dynamics and photocatalytic performance are systematically investigated. The S22− vacancies can significantly facilitate the separation of photogenerated charge carriers; while the S2− vacancies are demonstrated to not only promote the electron conduction and hole extraction in the photocatalytic process but also improve the kinetics of benzylamine oxidation. As a result, the use of defective ZrS3 NBs as photocatalyst produces H2O2 and benzonitrile at a high rate of 78.1 ± 1.5 and 32.0 ± 1.2 μmol h−1 respectively, under the illumination of a simulated sunlight.

Previous studies have shown that the oxidation potential of benzylamine lies higher than that of water, and the benzylamine oxidation was thus used to replace oxygen evolution reaction to couple with photocatalytic and electrocatalytic hydrogen evolution reaction14,17,55,56. This suggests the VBM of defective ZrS3 NBs lying far below the oxidation potential of benzylamine, indicating that these photocatalysts are applicable to the photocatalytic O2 reduction and benzylamine oxidation.Based on the high activity of ZrS1-yS2-x(15/100) for H2O2 generation, we further utilized benzylamine to substitute the hole scavenger. The H2O2 evolution rate of ZrS1-yS2-x(15/100) was decreased to 78.1 ± 1.5 μmol h−1 with the same molar amount of benzylamine as benzyl alcohol, due to the slower oxidation kinetics of benzylamine than that of benzyl alcohol. Simultaneously, the benzylamine was oxidized and converted to benzonitrile at a rate of 32.0 ± 1.2 μmol h−1 with a high selectivity of 99%, and no other by-products were detected by the Gas Chromatography-Mass Spectrometry measurements, consistent with the previous report14,29. Besides, the ZrS1-yS2-x(15/100) photocatalyst shows the rates for decomposition of H2O2 of 0.14 and 0.16 h−1 with the presence of benzyl alcohol and benzylamine, respectively, and the rates for formation of H2O2 of 125 and 113 μmol h−1 with the presence of benzyl alcohol and benzylamine, respectively.