Rugae-like FeP nanocrystal assembly on a carbon cloth: an exceptionally efficient and stable cathode for hydrogen evolution

• Published in: Nanoscale Vol. 7; no. 25; pp. 10974 - 10981
• Main Authors: Yang, Xiulin, Lu, Ang-Yu, Zhu, Yihan, Min, Shixiong, Hedhili, Mohamed Nejib, Han, Yu, Huang, Kuo-Wei, Li, Lain-Jong
• Format: Journal Article
• Language: English
• Published: England 07.07.2015
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/C5NR02375K

There is a strong demand to replace expensive Pt catalysts with cheap metal sulfides or phosphides for hydrogen generation in water electrolysis. Earth-abundant Fe can be electroplated on carbon cloth (CC) to form high surface area rugae-like FeOOH assembly. Subsequent gas phase phosphidation converts the FeOOH to FeP or FeP 2 and the morphology of the crystal assembly is controlled by the phosphidation temperature. FeP prepared at 250 °C presents lower crystallinity and that prepared at higher temperatures of 400 °C and 500 °C possesses higher crystallinity, but lower surface area. The phosphidation at 300 °C produces nanocrystalline FeP and preserves the high-surface area morphology; thus, it exhibits the highest HER efficiency in 0.5 M H 2 SO 4 , i.e. , the required overpotential to reach 10 and 20 mA cm −2 is 34 and 43 mV, respectively. These values are lowest among the reported non-precious metal phosphides on CC. The Tafel slope for FeP prepared at 300 °C is around 29.2 mV dec −1 , which is comparable to that of Pt/CC; this indicates that the hydrogen evolution for our best FeP is limited by the Tafel reaction (same as Pt). Importantly, the FeP/CC catalyst exhibits much better stability in a wide-range working current density (up to 1 V cm −2 ), suggesting that it is a promising replacement of Pt for HER.