PNNL

Abstract

A long-standing challenge in molecular electrocatalysis is to design catalysts that break away from the tradeoff between rate and overpotential arising from electronic scaling relationships. Here we report an inversion of the rate-overpotential correlation through system-level design of new [Ni(PR2NR'2)2]2+ electrocatalysts for the production of H2. The overpotential is lowered by an electron-withdrawing ligand, while the turnover frequency is increased by controlling the catalyst structural dynamics, using both ligand design and solvent viscosity. The cumulative effect of controlling each of these system components is an electrocatalyst with a turnover frequency of 70,000 s–1 and an overpotential of 230 mV, corresponding to a 100-fold rate enhancement and a 170 mV reduction in overpotential compared to the parent nickel catalyst. The success of this system-level approach originates from the detailed mechanistic understanding of these catalysts, which enabled modifications of the catalyst and solvent to disfavor non-productive pathways. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for DOE.