Nickel nanoparticles modified CdS - A potential photocatalyst for hydrogen production through water splitting under visible light irradiation

Ni nanoparticles were prepared via chemical reduction of aqueous NiCl2·6H2O by N2H4·H2O, and loaded on the surface of CdS by photo-induced electrons as water splitting reaction was occurring. Resultant CdS modified with Ni nanoparticles (denoted as Ni/CdS) was characterized by transmission electron microscopy, X-ray diffraction, UV-vis diffuse reflectance spectrometry, and photoluminescence spectrometry, and its photocatalytic performance for water splitting under visible light irradiation producing hydrogen was evaluated with a 300 W Xe lamp as the light source (λ ≥ 420 nm). It was found that as-obtained Ni nanoparticles with an average size of about 10 nm have face centered cubic structure, and they are preferentially deposited on the (100), (002), and (101) crystal planes of CdS nanorods to afford Ni/CdS photocatalyst. Besides, as-prepared Ni/CdS photocatalyst has a surface area of 28.8 m2/g (determined by BET method), higher than that of CdS nanorods, which indicates that Ni nanoparticles is beneficial to increasing the surface area of CdS nanorods. Moreover, as-prepared Ni/CdS photocatalyst shows absorption traits in the visible light region, and its photoluminescence peak intensity is lower than that of CdS, which means that Ni nanoparticles function as the trappers of photo-generated electrons to quench the photoluminescence of CdS. More importantly, although pristine CdS exhibits no activity for hydrogen production from water splitting under visible light irradiation, Ni/CdS photocatalyst with a Ni content of 4% (mass fraction) provides a hydrogen production rate of 25.848 mmol/(h g) (QE = 26.8%, λ = 420 nm) from water splitting of (NH4)2SO3 aqueous solution under the same testing condition and it retains a high stability and activity even after 20 h of water splitting. This demonstrates that Ni/CdS could be a promising candidate photocatalyst for visible light water splitting yielding hydrogen.