Fabrication of metal sulfide porous foams via electrodeposition and galvanic replacement reaction
Graphical abstract
Introduction
Photocatalysts are known as a type of semiconductor materials which have been attracted a great deal of attention due to their potential in environmental purification [1], [2], [3], [4] and hydrogen energy production [5], [6], [7]. As a result of fast development of nanotechnology a great deal of efforts has been devoted to the synthesis and characterization of nano and micro sized semiconductor structures [8], [9], [10]. Nanoporous foam materials represent a very promising type of structured materials having a number of interesting and unique properties [11], [12], [13] especially in heterogeneous catalysis [14], [15], [16]. Metal foams can be deposited electrochemically from a metal ion solution [17]. Direct electrochemical fabrication of 3-D foam of Cu metal, using hydrogen bubbles as a dynamic and effective template; with highly porous ramified (dendritic) walls have been reported [18].
Following on our previous work on the fabrication of Ag and Pd (noble metal) foam coated electrodes, [19], [20] we present the indirect fabrication of metal sulfide foams based on electrochemical deposition of a scarified Cu foam and galvanic replacement reaction. The groups of Adzic and Kokkinidis was first utilized the galvanic replacement reaction for preparation of metallic and bimetallic electrocatalysts [21], [22], [23], [24], [25], [26], [27]. In this study; the main goal is the fabrication of metal sulfide foams. Since foam materials have porous and ramified walls with high surface area, we decided to introduce a new, simple and fast method for fabrication of semiconductor foams.
Section snippets
Chemicals and apparatus
All reagents were of analytical grade and used without any further purification. Solutions were made with twice distilled water. All electrochemical experiments were performed using a Potentiostat & Galvanostat (Autolab, PGSTA, Eco Chemie, Netherlands). An Ag|AgCl|KCl (3 M) electrode and a platinum wire served as the reference and counter electrodes, respectively. The working electrodes used throughout this work were constructed with small pieces of high-purity Cu sheets (Merck). Scanning
Cu2S foam
The Cu foam is fabricated based on method reported in the literature [20], [28]. Then the as-fabricated Cu foam is simply immersed in a solution of 0.5 M Na2S for 1800 s. The possible reactions which resulted in the conversion of Cu foam to Cu2S foam could be summarized as [30], [31]:Cu2O+H2O+Na2S→Cu2S+2 NaOH
The morphology of the fabricated electrodes was observed by means of SEM. Fig. 1 depicts the 3D structures of Cu2S foam at different magnifications.
Conclusions
Porous metal sulfide foams were fabricated via electrodeposition and galvanic replacement reaction. Fabrication of metal sulfide foam electrodes in this article show several benefits. First, the procedure is very simple and fast. Second, the process is environmentally friendly, and it can be performed using commercially available reagents in water as a green solvent with no need to any additive. Finally, it does not require rigid condition such as high temperature and high pressure apparatus so
Acknowledgments
We are grateful for the financial support of the Vice chancellorships for research and technology of the University of Isfahan.
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