Hybrid Dot–Disk Au-CuInS₂ Nanostructures as Active Photocathode for Efficient Evolution of Hydrogen from Water

Abstract

The synthesis of hybrid 0D-2D dot−disk Au-CIS heterostructures is enabled through nucleating wurtzite ternary I−III−VI CuInS 2 (CIS) semiconductor nanostructures on cubic Au particles via thiol-activated interface reactions. Chemistry of formation of these unique hybrid metal− semiconductor nanostructures is established by correlating successive X-ray diffraction patterns and microscopic images. Furthermore, these nanostructures are explored as an efficient photocathode material for photoelectrochemical (PEC) production of hydrogen from water. Although CIS nanostructures are extensively used as PEC active materials for solar-tohydrogen conversion, the coupled structures with Au for their exciton−plasmon coupling is observed in producing a higher photocurrent with efficient evolution of hydrogen. In the comparison of materials properties, it is observed that the cathodic photocurrent, onset potential, and the half-cell solar-to-hydrogen efficiency (HC-STH) are recorded to be superior to all CISbased photocathodes reported up to the current time. These results suggest that designing proper heterostructured functional materials can enhance the hydrogen production in the PEC cell and would be helpful for the ongoing technological needs for a greener way of generating and storing hydrogen energy. ■ INTRODUCTIONHydrogen evolution from solar water splitting, a possible alternative way of generating green energy, is on the forefront of current research. 1−6 In this aspect, photoelectrochemical (PEC) solar-to-hydrogen conversion remains as a promising approach and has been studied extensively. 1,7−14 The performance of the PEC cell and the efficiency of hydrogen evolution typically depend on the effectiveness of the involved photoactive electrode material. Among these, semiconducting nanomaterials having absorption in the solar spectrum, high excitonic coefficient, and high charge carrier mobility are more focused. 15−17 Moreover, electrodes are also designed following proper band engineering with other materials for feasible transfer of the photoexcited electron to water. 15,17−20 In recent developments, even success has been obtained to a large extent for improving the PEC cell performance using different nanomaterials, but finding more efficient and stable materials for boosting the cathodic current and enhancing the efficiency of hydrogen evolution in a single building block are still in demand.Among the different developed functional photoactive materials, noble metal−semiconductor heterostructures have recently emerged as ideal photocatalytic materials where the semiconductor generates the charge carriers and metal acts as a sink for trapping the electron. 21−32 For the case of metal Au, the electron transfer is even more facilitated as the surface plasmon of Au couples with semiconductor exciton and enhances the excited state lifetime of the photoelectron. 33−38 Among the semiconductor counter parts, for high carrier mobility and high extinction coefficient, multinary materials are recently more focused. 22,23,35,3...

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