Transition-metal phosphides have received recent attention as non-oxide catalytic materials for the electrochemical water splitting hydrogen evolution reaction (HER). Most metal phosphide phase diagrams reveal a broad range of crystalline M-P structures with widely varying compositions. Some have recognized lithium intercalation battery potential, while others catalytically facilitate the thermal desulfurization or denitrogenation of transportation fuels. Most metal phosphides examined for HER activity are produced by precursor routes that yield metal-rich or monophosphide products such as MoP, CoP, Ni2P, or Cu3P. Our research efforts have identified an air and solvent-free method to produce a range of 3d and 4d phosphorus-rich metal phosphides including: FeP3, CoP3, NiP2, CuP2, AgP2, and PdP2. This synthetic method relies on a thermochemical driving force of both product formation and volatile PCl3 elimination by 500 °C. Reactions occur between metal halides and phosphorus vapor (from red P volatilization to P4 by ~450 °C) to produce MPx and PCl3 in an etching-like process. In contrast to the metal-rich phosphide structures that have extensive metal-metal bonding, phosphorus-rich metal phosphides typically consist of structures with polyphosphide anions that surround single metal centers. This presentation will relay results of our attempts to make intimate mixtures of two elements in a MP2 material using this method [e.g., (Ni,Pd)P2 and (Cu,Ag)P2] and also initial work on growth of metal phosphides onto other supports (carbon and oxide powders). Electrochemical HER and oxygen evolution reaction [OER] results for binary phosphides and mixed metal systems will be described. Stability testing on several of the single metal MP2 and MP3 systems will also be presented along with comparisons to analogous metal-rich phosphides. Comparisons of local structures (atomic and electronic) for metal-rich and phosphorus-rich phosphides will be described.

Synthesis and catalytic reactions with 3d and 4d phosphorus-rich metal phosphides

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.