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

ABSTRACT: Films of CoP have been electrochemically synthesized, charac-terized, 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 − 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 chronopotentiom-etry. 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· Co2O3) and of phosphorus as phosphide and orthophosphate. The orthophos-phate species, produced by air-oxidation, were eliminated upon HER electrocatalysis in sulfuric acid. The operando fil