Electrocatalytic Performance and Stability of Nanostructured Fe–Ni Pyrite-Type Diphosphide Catalyst Supported on Carbon Paper

详细信息    查看全文

• 作者：José Diogo Costa ; José Luis Lado ; Enrique Carbó-Argibay ; Elvira Paz ; Juan Gallo ; M. Fátima Cerqueira ; Carlos Rodríguez-Abreu ; Kirill Kovnir ; Yury V. Kolen’ko
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：August 4, 2016
• 年：2016
• 卷：120
• 期：30
• 页码：16537-16544
• 全文大小：550K
• 年卷期：0
• ISSN：1932-7455

文摘

A simple and effective method to prepare an active and stable nanostructured working electrode for electrochemical water splitting is described. Specifically, mixed Fe–Ni diphosphide was prepared by sputtering a 200-nm-thick layer of Permalloy onto carbon paper gas diffusion layer followed by gas transport phosphorization reaction. The mass density of the resultant diphosphide phase was established to be ≈1.1 mg/cm². Energy-dispersive X-ray microanalysis shows that the actual elemental composition of the resultant ternary electrocatalyst is approximately Fe_0.2Ni_0.8P₂, while the powder X-ray diffraction analysis confirms that the electrocatalyst crystallizes in NiP₂ cubic pyrite-like structure. As a cathode for hydrogen evolution reaction (HER) in acidic and alkaline electrolytes, this earth-abundant electrode has exchange current densities of 6.84 × 10^–3 and 3.16 × 10^–3 mA/cm² and Tafel slopes of 55.3 and 72.2 mV/dec, respectively. As an anode for oxygen evolution reaction (OER) in alkaline electrolyte, the electrode shows an exchange current density of 2.88 × 10^–4 mA/cm² and Tafel slope of 49.3 mV/dec. The observed high activity of the electrode correlates well with its electronic structure, which was assessed by density functional theory (DFT) calculations. The stability of Fe_0.2Ni_0.8P₂ electrocatalyst in HER and OER was evaluated by means of accelerated degradation test and chronopotentiometry. The results of these experiments elucidate partial dissolution and entire chemical transformation of Fe_0.2Ni_0.8P₂ as the main mechanisms of the electrode degradation during HER and OER, respectively. Overall, our findings could facilitate the composition-based design of active, stable, and durable phosphide electrodes for electrochemical water splitting.