Heterojunction engineering of n-ZnS_xO_1-x:Ni,Mn and p-MnS₂ electrospun microfiber for efficient solar-driven hydrogen evolution

An n-type Ni–Mn-codoped ZnS_xO_1-x/p-type MnS₂ (ZNM-x) nanocomposite microfiber catalyst has been successfully synthesized with an electrospinning method with different Mn contents for photocatalytic hydrogen evolution reaction. The as-prepared catalysts have been identified with different characterization and analysis of XRD, SEM, TEM, XPS, DRS, PL, and electrochemical measurements, including EIS, CV, and Mott Schottky. Increasing Mn contents in ZNM-x catalyst induces different optical and electrochemical properties, leading to different photocatalytic HER performances. The identified ZNM-5 with a solid-solution formation improves the HER rate up to 8947 μmol/g and ZNM-25 with simultaneous solid-solution and p-n heterojunction formations further enhances the HER rate to 10692 μmol/g. The great photocatalytic HER performances are owed to the effective photocarrier separation due to the formation of substitutional defects and p-n heterojunction. Besides the oxygen vacancy, the substitutional defects from Ni and Mn incorporation create positively charged species on catalyst surfaces and improve the catalytic activity. In addition, the ZNM-25 microfiber exhibits the photocatalytic HER capability for a long-term application with 25-h reusability without significant degradation. Based on the achieved performances, the electrospun ZNM-25 microfiber catalyst without nanoparticle leaching can be a prominent solution for energy and environmental issues.