ZnO/NiO Nanocomposite with Enhanced Photocatalytic H2 Production

Abstract

Inorganic photocatalytic materials exhibiting a highly efficient response to ultraviolet-visible light spectrum have become a subject of widespread global interest. They offer a substantial prospect for generating green energy and mitigating water pollution. Zinc oxide (ZnO), among various semiconductors, proves advantageous for water-splitting applications due to its elevated reactivity, chemical stability, and nontoxic nature. However, its efficacy as a photocatalyst is hindered by limited light absorption capacity and swift charge carrier recombination. To improve charge separation and enhance responsiveness to ultraviolet-visible light photocatalysis, the formation of a heterojunction with another suitable semiconductor is beneficial. Thus, we employed hydrothermal route for the synthesis of the samples, which is a high-pressure method. The formations of ZnO/NiO heterostructures were revealed by scanning electron microscopy, X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The nanocomposites were discovered to have a substantially higher photocatalytic activity for the generation of H2. The H2 production rates show that ZnO (i.e., 168.91 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"><a:mi>μ</a:mi></a:math> molg-1 h-1) exhibits good H2 production rates as compared to NiO (i.e., 135.74 <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"><c:mi>μ</c:mi></c:math> molg-1 h-1). The best production rates were observed for ZN-30 (i.e., 247.56 <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"><e:mi>μ</e:mi></e:math> molg-1 h-1) which is 1.46 times greater than ZnO and 1.82 times greater than NiO. This enhanced photocatalytic activity for ZN-30 is because of the good electron-hole pair separation due to the formation of depletion layer, suppression of fast charge recombination, and overcoming resistance corrosion.

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