We have studied [Ni(P2N2)2]2+ electrocatalysts for production of H2 for several years, and have gained an understanding of the mechanism that leads to an improvement of the turnover frequencies of catalysis and lowering of the overpotential. The overpotential is decreased by incorporating an electron-withdrawing CF3 group on the aryl group on the phosphine. Long alkyl chain hydrocarbons substituted on the phenyl ring of the pendant amine lead to slower boat-chair isomerization of the ligand, disfavoring non-productive pathways. The turnover frequencies for catalysis inversely correlate with the boat-chair conformational change. Compared to acetonitrile, succinonitrile and adiponitrile are more viscous, and the more viscous solvents lead to slower structural dynamics of the ligand, providing further increases in rate. Controlling all of these system components leads to a turnover frequency of 70,000 s-1 at an overpotential of 230 mV.

Increasing rates and lowering overpotentials in [Ni(P2N2)2]2+ electrocatalysts for production of H2

255th National Meeting (2018)

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