Low-Symmetry Phthalocyanine Cobalt Bis(dicarbollide) Conjugate for Hydrogen Reduction

The synthesis and characterization of two new A₃B type unsymmetrical zinc phthalocyanines, one bearing a hydroxyl group and the other bearing a cobalt bis(dicarbollide) unit, are reported here. The introduction of diethylaminophenoxy moieties to the phthalocyanine fragments yields outstanding solubilities in organic solvents, as well as providing electropolymerization on the surface of the electrode. These modified electrodes are found to be effective for the electrocatalytic reduction of hydrogen ions in acidic media. The enhanced hydrogen-evolution reaction (HER) performance for the bis(dicarballide)-functionalized phthalocyanine-modified electrode can be simultaneously observed. This is attributed to its redox-active metal center of cobalt bis(dicarbollide), creating a synergistic effect, to facilitate many more electrocatalytic active sites, resulting in improved HER performance. The catalyst shows an onset potential of 163 mV at a current density of 8.79 µA cm^–2, and a Tafel slope as low as 28 mV dec^–1.