CoP as an Acid-Stable Active Electrocatalyst for the Hydrogen-Evolution Reaction: Electrochemical Synthesis, Interfacial Characterization and Performance Evaluation

详细信息    查看全文

• 作者：Fadl H. Saadi ; Azhar I. Carim ; Erik Verlage ; John C. Hemminger ; Nathan S. Lewis ; Manuel P. Soriaga
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：December 18, 2014
• 年：2014
• 卷：118
• 期：50
• 页码：29294-29300
• 全文大小：472K
• ISSN：1932-7455

文摘

Films of CoP have been electrochemically synthesized, characterized, and evaluated for performance as a catalyst for the hydrogen-evolution reaction (HER). The film was synthesized by cathodic deposition from a boric acid solution of Co²⁺ and H₂PO₂^{鈥?/sup> on copper substrates followed by operando remediation of exogenous contaminants. The films were characterized structurally and compositionally by scanning-electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman spectrophotometry. The catalytic activity was evaluated by cyclic voltammetry and chronopotentiometry. Surface characterization prior to electrocatalysis indicated that the film consisted of micrometer-sized spherical clusters located randomly and loosely on a slightly roughened surface. The composition of both the clusters and surface consisted of cobalt in the metallic, phosphide, and amorphous-oxide forms (CoO路Co₂O₃) and of phosphorus as phosphide and orthophosphate. The orthophosphate species, produced by air-oxidation, were eliminated upon HER electrocatalysis in sulfuric acid. The operando film purification yielded a functional electrocatalyst with a Co:P stoichiometric ratio of 1:1. After the HER, the surface was densely packed with micrometer-sized, mesa-like particles whose tops were flat and smooth. The CoP eletrodeposit exhibited an 85 mV overvoltage (畏) for the HER at a current density of 10 mA cm鈥? and was stable under operation in highly acidic solution, with an increase in 畏 of 18 mV after 24 h of continuous operation. The comparative HER catalytic performance of CoP, film or nanoparticles, is as follows: 畏_Pt < 畏_CoP聽film = 畏_CoP聽NP, 畏_Ni2P < 畏_CoSe2 < 畏_MoS2 < 畏_MoSe2.}