Electrodeposition of Sn-Ni Alloy Coatings for Water-Splitting Application from Alkaline Medium
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HYDROGEN is considered a secondary source of energy and is commonly referred as an energy carrier since it does not exist on Earth as a gas and must be separated from other compounds. Two of the most common methods used for the production of hydrogen are water splitting and steam reforming.[1] Although steam reforming is a less expensive method, it is not suggested for wide use due to the usage of methane (fossil fuel), leading to greenhouse gas emissions, which is linked to global warming. Another method is water electrolysis or water splitting, which passes an electric current to separate water into its basic elements, hydrogen and oxygen. Although water electrolysis is not the cheapest method for hydrogen production, it is preferred due to its high degree of purity.[2] Hence, searching for new and effective electrode materials for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of water splitting is very important in advanced industrial applications. Various materials have been used as efficient and durable cathodic electrocatalysts for the HER.[3] Noble metals (Pt, Ru, etc.) seem to be the most active and stable materials, but their extremely high cost and limited natural abundance impede their wide industrial applications. Thus, nonplatinum-active metals such as Fe, Ni, or Co as well as SANDHYA SHETTY, Ph.D. Research Scholar, and A. CHITHARANJAN HEGDE, Professor, are with the Electrochemistry Research Lab, Department of Chemistry, National Institute of Technology Karnataka, Surathkal, Srinivasnagar 575025, India. Contact e-mail: [email protected] Manuscript submitted February 5, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
their alloys and composites have received great attention as electrocatalysts for the HER because of their relatively low prices and accessibility.[4–14] In this direction, Arul Raj[15–17] accompanied by Vasu[15,18] examined several Ni-based alloys (binary and ternary) as cathodes for HER in alkaline water electrolysis, chlor-alkali cells, chlorate cells, etc. For this objective, they alloyed Ni with transition metals such as molybdenum, zinc, cobalt, tungsten, iron, and chromium via electrodeposition. This investigation revealed that the electrocatalytic activity of these alloys for HER on steel substrate is in the following order: Ni-Mo > Ni-Zn > Ni-Co > Ni-W > Ni-Fe > Ni-Cr > Ni. On the other hand, the literature review reveals that electrodeposited Sn-Ni alloys are good electrocatalytic materials for HER in alkaline solutions,[19–22] and they are found to be better than Raney-Ni electrode.[23] Yamashita et al.[19] investigated the relationship between the catalytic activity for HER and characteristics of the Ni-Sn alloy prepared by electroplating. Santos[20] also reported that the electroplated Sn-Ni alloys exhibit low overpotential for the HER in alkaline solution. The recent report[24] demonstrated that the chemical composition, phase composition, and morphology of the Sn-Ni alloy coatings depend on the deposition current density (c.d.). Furthermore, the o
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