Pressurized Formic Acid Dehydrogenation: An Entropic Spring Replaces Hydrogen Compression Cost

An Immobilized (Carbene)Nickel Catalyst for Water Oxidation

The oxygen evolution reaction (OER) of water splitting is essential to electrochemical energy storage applications. While nickel electrodes are widely available heterogeneous OER catalysts, homogeneous nickel catalysts for OER are underexplored. Here we report two carbene-ligated nickel(II) complexes that are exceptionally robust and efficient homogeneous water oxidation catalysts. Remarkably, these novel nickel complexes can assemble a stable thin film onto a metal electrode through poly-imidazole bridges, making them supported heterogeneous electrochemical catalysts that are resilient to leaching and stripping. Unlike molecular catalysts and nanoparticle catalysts, such electrode-supported metal-complex catalysts for OER are rare and have the potential to inspire new designs. The electrochemical OER with our nickel-carbene catalysts exhibits excellent current densities with high efficiency, low Tafel slope, and useful longevity for a base metal catalyst. Our data show that imidazole carbene ligands stay bonded to the nickel(II) centers throughout the catalysis, which allows the facile oxygen evolution.

Recycling Organoiridium Waste to [(1,5-Cyclooctadiene)IrCl]2

We report the first process for iridium element recovery from organoiridium waste that is quantitative, pyrolysis-free, and generates no iridium metal. The key step is oxidative degradation of the waste by bleach to crude iridium(IV) hydroxide. Its treatment with hydrazine and then hydrogen peroxide gives synthetically important hexachloroiridic acid, which is converted to [(1,5-cyclooctadiene)IrCl]2 in 87% yield.