Samarium as a Catalytic Electron-Transfer Mediator in Electrocatalytic Nitrogen Reduction to Ammonia
Emily A. Boyd, Hoimin Jung, Jonas C. Peters
Abstract
High Resolution Image Download MS PowerPoint Slide Samarium diiodide (SmI 2 ) exhibits high selectivity for N 2 R catalyzed by molybdenum complexes; however, it has so far been employed only as a stoichiometric reagent (0.3 equiv of NH 3 per Sm) combined with coordinating proton sources (e.g., H 2 O, ROH). The latter inhibit catalytic turnover of Sm III owing to buildup of stable hydroxide/alkoxide sinks. Here, we report a tandem Sm/Mo-catalyzed e N 2 R system that achieves the lowest overpotential and highest Faradaic efficiency (82%) reported to date for nonaqueous e N 2 R at ambient pressure. Up to 8.4 equiv of NH 3 is produced per Sm, representing a 25-fold increase over N 2 R with stoichiometric SmI 2 . A noncoordinating proton source enables electrochemical SmI 3 /SmI 2 cycling at the applied potential of −1.45 V vs Fc +/0 .