A facile synthesis of ZnxCd1−xS/CNTs nanocomposite photocatalyst for H2 production

Abstract

The sulfide solid solution has become a promising and important visible-light-responsive photocatalyst for hydrogen production nowadays. Zn(x)Cd(1-x)S/CNT nanocomposites were synthesized to improve the dispersion, adjust the energy band gap, and enhance the separation of the photogenerated electrons and holes. The as-prepared photocatalysts were characterized by scanning electron-microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectra (UV-visible), respectively. And the effects of CNTs on structure, composition and optical absorption property of the sulfide solid solutions were investigated along with their inherent relationships. For Zn0.83Cd0.17S/CNTs, sulfide solid solution is assembled along the CNTs orderly, with a diameter of 100 nm or so. XPS analysis shows that there is bonding effect between the solid solutions and the CNTs due to the strong adsorption of Zn(2+) and Cd(2+) on the surface of CNTs. There are two obvious absorption edges for Zn0.83Cd0.17S/CNTs, corresponding to two kinds of sulfide solid solutions with different molar ratios of Zn/Cd. The hybridization of solid solutions with CNTs makes the absorption spectrum red shift. The photocatalytic property was evaluated by splitting Na2S + Na2SO3 solution into H2, and the highest rate of H2 evolution of 6.03 mmol h(-1) g(-1) was achieved over Zn0.83Cd0.17S/CNTs. The high activity of photocatalytic H2 production is attributed to the following factors: (1) the optimum band gap and a moderate position of the conduction band (which needs to match the irradiation spectrum of the Xe lamp best), (2) the efficient separation of photogenerated electrons and holes by hybridization, and (3) the improvement of the dispersion of nanocomposites by assembling along the CNTs as well.

An Efficient, Visible‐Light‐Driven, Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

“…According to X‐ray photoelectron spectra (XPS, Figure S16) of NiS/Zn 0.5 Cd 0.5 S, the peaks of Zn 2p 3/2 (1023.9 eV), Zn 2p 1/2 (1046.9 eV), Cd 3d 5/2 (404.8 eV) and Cd 3d 3/2 (411.6 eV) are all sharp and symmetrical, demonstrating that the valences of Zn and Cd are both +2 . A weak peak is present at 857.2 eV due to the small amount of Ni in NiS/Zn 0.5 Cd 0.5 S. Two peaks at 161.2 eV and 162.4 eV divided from S 2p peak can be attributed to the S 2p 3/2 and S 2p 1/2 levels, respectively .…”

Real roles of perylenetetracarboxylic diimide for enhancing photocatalytic H2-production

“…For bare Zn x Cd 1 À x S solid solutions, under solar irradiation, electrons are excited from the valence band (VB) populated by S 3p to the formed CB by hybridizing Zn 4s4p with Cd 5s5p [15], and creates holes in VB. Generally, these charge carriers recombine rapidly before reaching the surface to reduce the H þ .…”

“…However, further improvement of the photocatalytic efficiency was retarded by factors such as a high recombination rate of photogenerated electronÀ hole pairs. Many attempts have been tried to suppress this recombination, including loading cocatalyst such as metal sulfides [11], metal oxides [12,13], and carbon nanotubes [14,15], to alternatively trap the photogenerated electrons or holes, or by doping with other metals to promote the charge separation and/or function as separated redox reaction sites [16,17].…”

GSH-assisted hydrothermal synthesis of MnxCd1−xS solid solution hollow spheres and their application in photocatalytic degradation

“…Considering that the solid solutions can be obtained by combining a narrowband-gap material with a wide-band-gap material, or even two wide-band-gap materials, thus the solid solutions with a proper band structure may be formed by choosing and adjusting the right components. To present, a huge number of multi-component solid solutions formed by CdS were reported successively, such as Zn x Cd 1 À x S [14,24], Mn 1 À x Cd x S [25], (CuIn)xCd 2(1 À x) S 2 [26], Zn 1 À x Cd x In 2 S 4 [27,28], Cd x Cu y Zn 1 À x-y S [29], (Zn x Cd 1 À x )(Se x S 1 À x ) [30], Cd 0.1 Sn x Zn 0.9-2x S [31], Cu-doped Cd 0.1 Zn 0.9 S [32] and Zn x Cd 1 À x S/CNTs [33], et al Among them, the ternary Mn-Cd-S alloyed system formed by combining MnS (E g ¼3.7 eV) with CdS (E g ¼2.4 eV) has attracted considerable attention [34][35][36]. MCS solid solution, due to the tunability of its band gap by regulating the contents of Cd and Mn, is a promising candidate for visible light catalysis.…”