Remarkable stability of a molecular ruthenium complex in PEM water electrolysis

The dinuclear Ru diazadiene olefin complex, [Ru (OTf)(μ-H)(Me dad)(dbcot) ], is an active catalyst for hydrogen evolution in a Polymer Exchange Membrane (PEM) water electrolyser. When supported on high surface area carbon black and at 80 °C, [Ru (OTf)(μ-H)(Me dad)(dbcot) ]@C evolves hydrogen at the cathode of a PEM electrolysis cell (400 mA cm , 1.9 V). A remarkable turn over frequency (TOF) of 7800 mol mol h is maintained over 7 days of operation. A series of model reactions in homogeneous media and in electrochemical half cells, combined with DFT calculations, are used to rationalize the hydrogen evolution mechanism promoted by [Ru (OTf)(μ-H)(Me dad)(dbcot) ].