Enhancing electrocatalytic activity of bifunctional Ni 3 Se 2 for overall water splitting through etching-induced surfac
- PDF / 558,368 Bytes
- 9 Pages / 584.957 x 782.986 pts Page_size
- 101 Downloads / 232 Views
Electrocatalysts for oxygen evolution reaction (OER) has been at the center of attention for water splitting reactions. In this article we have presented a methodology to significantly improve the OER catalytic efficiency of electrodeposited Ni3Se2 films. Specifically, the pristine Ni3Se2 on surface nanostructuring induced through electrochemical etching shows a remarkable decrease of overpotential (@10 mA cm2) to 190 mV, making it as one of the best OER elecrocatalyst known till date. Through detailed structural and morphological characterization of the catalyst film, we have learnt that such enhancement is possibly caused by the increased surface roughness factor and electrochemically active surface area of the etched film. The morphology of the film also changed from smooth to rough on etching further supporting the enhanced catalytic activity. Detailed characterization also revealed that the composition of the film was unaltered on etching. Ni3Se2 film was also active for HER in alkaline medium making this a bifunctional catalyst capable of full water splitting in alkaline electrolyte with a cell voltage of 1.65 V.
I. INTRODUCTION
In this era of exploring alternative and sustainable energy resources, catalyst aided water splitting plays a substantial role. However, basic electrochemical water splitting is associated with substantial energy loss, fundamentally due to the high overpotentials required at the anode corresponding to the oxygen evolution reaction (OER). Although traditionally precious metal oxides such as RuOx and IrOx were viewed as efficient water oxidation catalysts,1–3 scarcity of the raw materials and their high cost has been prohibitive for wide scale practical applications of these catalysts. To circumvent this issue, over the past several years, researchers have delved deeper into transition metal oxides as OER electrocatalyst with performance comparable to the precious metal oxides.4–23 More recently, new families of OER electrocatalysts has been identified comprising of transition metal chalcogenides MxEy (M 5 Ni, Fe, Co; E 5 S, Se),24–28 some of which outperform even the transition metal oxides.26,27 Some of the major advantages of using chalcogenides over oxides is that the electronegativity of S, Se, and Te being smaller than O, metal-chalcogen bonds show a higher degree of covalency, which leads to decreasing band gap energy, as well as raising the valence band edge to be more closer to the water oxidation level. In fact theoretical band structure calculations have shown that the band gap and band edge Contributing Editor: Xiaobo Chen a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.301
energies does show a progressive change (decreasing band gap and increasing valence band edge energy) from oxides to tellurides.29,30 While most of the transition metal oxides are wide band gap semiconductors, the selenides and tellurides are mostly semimetal or metallic. Additionally, the transition metal chalcogenides are known to form a wide range of stoichiometries s
Data Loading...
