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, at Pacific Northwest National Laboratory (PNNL), has published details about another new catalyst (see previous post New PNNL Catalyst.) The work was conducted by Smith, S. E., Yang, J. Y., DuBois, D. L. and Bullock, R. M. (2012), "Reversible Electrocatalytic Production and Oxidation of Hydrogen at Low Overpotentials by a Functional Hydrogenase Mimic," Angewandte Chemie International Edition, doi: 10.1002/anie.201108461.
The new reversible hydrogen catalyst is based on a nickel-based complex, and has been developed for more than two years. Nickel was selected due to its low cost and abundance, relative to platinum (the conventional reversible hydrogen catalyst.) But unlike solid platinum, this new catalyst is a homogeneous catalyst. In other words, unlike platinum, this catalyst dissolves in a solution. This is a problem for a conventional fuel cell, in that a soluble catalyst will get "washed out" of the fuel cell, and not be available for chemical reactions. Future PNNL work will likely be aimed towards immobilzing the catalyst, so that it can be used in conventional electrochemical conversion devices.
The new bis(diphosphine) nickel(II) complex (see picture) is has a nickel core, with phosphine ligands extending from the nickel center. The catalyst has reversible electrocatalytic activity for hydrogen production and oxidation at low overpotentials, which are characteristic for hydrogenase enzymes. "This [catalyst] has a lower overpotential than we usually find," said Morris Bullock, PhD, Director of the Center for Molecular Electrocatalysis. "Sadly, it is also slow."
Hopefully Bullock and associates can continue improving the catalyst, including improving its speed (the kinetics), and make a catalyst that is useful for electrochemical energy conversion. Good luck!