CoSe2 and NiSe2 Nanocrystals as Superior Bifunctional Catalysts for Electrochemical and Photoelectrochemical Water Splitting

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• 作者：In Hye Kwak ; Hyung Soon Im ; Dong Myung Jang ; Young Woon Kim ; Kidong Park ; Young Rok Lim ; Eun Hee Cha ; Jeunghee Park
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：March 2, 2016
• 年：2016
• 卷：8
• 期：8
• 页码：5327-5334
• 全文大小：574K
• ISSN：1944-8252

文摘

Catalysts for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) are central to key renewable energy technologies, including fuel cells and water splitting. Despite tremendous effort, the development of low-cost electrode catalysts with high activity remains a great challenge. In this study, we report the synthesis of CoSe₂ and NiSe₂ nanocrystals (NCs) as excellent bifunctional catalysts for simultaneous generation of H₂ and O₂ in water-splitting reactions. NiSe₂ NCs exhibit superior electrocatalytic efficiency in OER, with a Tafel slope (b) of 38 mV dec^–1 (in 1 M KOH), and HER, with b = 44 mV dec^–1 (in 0.5 M H₂SO₄). In comparison, CoSe₂ NCs are less efficient for OER (b = 50 mV dec^–1), but more efficient for HER (b = 40 mV dec^–1). It was found that CoSe₂ NCs contained more metallic metal ions than NiSe₂, which could be responsible for their improved performance in HER. Robust evidence for surface oxidation suggests that the surface oxide layers are the actual active sites for OER, and that CoSe₂ (or NiSe₂) under the surface act as good conductive layers. The higher catalytic activity of NiSe₂ is attributed to their oxide layers being more active than those of CoSe₂. Furthermore, we fabricated a Si-based photoanode by depositing NiSe₂ NCs onto an n-type Si nanowire array, which showed efficient photoelectrochemical water oxidation with a low onset potential (0.7 V versus reversible hydrogen electrode) and high durability. The remarkable catalytic activity, low cost, and scalability of NiSe₂ make it a promising candidate for practical water-splitting solar cells.