Nickel Complex Boosts Hydrogen Oxidation

An improved nickel diphosphine complex catalyzes hydrogen oxidation with greater activity than previously reported molecular catalysts tested for that reaction, according to researchers at Pacific Northwest National Laboratory (PNNL), who synthesized the compound (Chem. Commun., DOI: 10.1039/c0cc03246h). Nanoparticulate platinum is the top-performing catalyst for hydrogen oxidation in fuel cells. But platinum’s high cost limits its widespread use, for example in automotive applications. Researchers working to develop substitutes for precious-metal catalysts have developed a number of nickel, cobalt, and iron complexes that catalyze a variety of reactions. Yet few of those compounds mediate electrocatalytic hydrogen oxidation, which separates hydrogen into protons and electrons and forms water upon reaction with oxygen. Previously, the most active molecular catalyst for hydrogen oxidation was a nickel diphosphine complex prepared at PNNL a few years ago. Now, that PNNL team, which includes Jenny Y. Yang, Daniel L. DuBois, and coworkers, has prepared another nickel catalyst that is five times as active as the earlier version. They report that the cyclohexyl diphosphine nickel complex with pendant amines functionalized with tert-butyl groups facilitates 50 “turnovers” per second in the presence of base and 1 atm of hydrogen.