1. Introduction
In recent decades, the excessive use of fossil fuels has led to a battery of energy shortages and environmental pollution questions [1, 2]. Compared with traditional fossil fuels, hydrogen is a clean and efficient energy carrier, since the H2 evolution from water splitting is one of the more promising methods with great promise to solve the problem [3, 4]. Noble metal Pt not only has excellent electron absorption ability, but also provides abundant active sites, thus Pt has superior performance in terms of hydrogen production [5]. While high cost and preciousness of Pt limit its large-scale application in industry [6]. Hence, it is a challenging task to develop novel photocatalyst with excellent activity and low-cost to replace noble metals.
The various semiconductor photocatalysts have been extensively studied, such as metallic sulfide (MoS2 [7], CdS [8], ZnS [9], CdxZn1-xS [10, 11]), metallic oxide (Co3O4 [12], Cu2O [13]), carbon-based materials (g-C3N4 [14]) and so on over the past decade. Among them, MnxCd1−xS solid was first reported in 2010 [15], it has attracted widespread attention due to their strong light absorption and adjustable energy band structures [16, 17]. Peculiarly, it overcomes the disadvantages of poor corrosion resistance and low activity of CdS, and it has highly efficient H2production activity. However, pure MnxCd1-xS still exhibits severe recombination of photo-induced carriers that limited its activity in photocatalytic reaction [18]. Thus, many effective strategies have been presented to solve this problem, such as elemental doping [19], constructing heterojunction [20], morphological tailoring [21] and so on. Thereinto, co-catalyst not only provide enough redox reaction sites, but also reduce activation potentials and accelerate the transfer of photo-generated electrons [22]. For example, Liu’s et al. [23] utilised the CoP nanoparticles to modify Mn0.2Cd0.8S nanowires and significantly improved hydrogen production activity.
The mainly Ni-based co-catalysts were widely developed in the field of photocatalytic hydrogen production [24, 25], including Ni2P, NiSx and Ni(OH)2etc. As one of the Ni-based materials, NiSe2 collects the advantages of high light absorption conversion ability, reduced band gap and remarkable conductivity in terms of photoelectricity [26, 27]. Secondly, it has low cost and yields more [28, 29]. Chen and co-workers [30] used CdS and NiSe2 to build a p-n heterojunction to improve hydrogen production activity. However, NiSe2 has been widely studied mostly in the field of eletrocatalysis, and there are few reports on photocatalytic hydrogen production. In addition to the strategy of adding co-catalysts, by adjusting and controlling the morphology, size and microstructure of nanomaterials, the composite material giving rising to distinct optical and mechanical properties, which is also a promising optimization method [31]. The hierarchical three dimensional (3D) structures could availably inhibit the stacking or aggregation of nanoparticles than two dimensional (2D) nanosheet materials [32]. On the other hand, the surface of the 3D structure can provide a large number of reaction sites and promote charge transfer efficiency [31], which enhanced to the photocatalytic activity.
Inspired by aforementioned discussion, in this work, we developed a facile method to incorporate 0D Mn0.05Cd0.95S into 3D NiSe2. Through a series of detailed characterizations of the composition, microstructure, BET surface areas and optical properties of Mn0.05Cd0.95S/NiSe2composites, the effect of NiSe2 was researched on the activity of material. In addition, we proposed a possible mechanism of Mn0.05Cd0.95S/NiSe2composite based on the conclusions of photoelectrochemical measurements and photoluminescence spectroscopy.