The ability to efficiently and cost-effectively convert solar energy to molecular hydrogen through water splitting is necessary for meeting rising energy demands and to mitigate the adverse effects of carbon-based fuels on the environment. Practical electrochemical and photoelectrochemical energy devices require the immobilization of stable and active hydrogen evolving catalysts onto electrodes and photocathode materials, which remains a significant challenge. Heterogenization of molecular catalysts has emerged as a viable immobilization strategy which combines the advantageous properties of homogeneous and heterogeneous catalysis. We have demonstrated that cobalt (II) reacts with benzene-1,2,4,5-tetrathiol, a dinucleating ligand, in the presence of base to form a cobalt dithiolene coordination polymer, which can readily be immobilized onto glassy carbon electrodes (GCE) and planar p-type Si(100). The polymer modified GCE required an overpotential of 560 mV to reach 10 mA/cm2 of activity in aqueous pH 1.3 solutions. Furthermore, polymer modified Si photocathodes achieved photocurrents up to 3.8 mA/cm2 at 0 V vs RHE under simulated 1 Sun illumination demonstrating the successful utilization of solar energy to facilitate the reduction of protons from acidic water. We have expanded this methodology to the formation of a variety of metal chalcogenide coordination polymers and explored their electrochemical H2 evolving activity in acidic aqueous media. Through simple modifications of the ligand scaffold and/or metal center, we have systematically investigated the ability to tune important catalytic parameters of the coordination polymers such as overpotential and stability under exposure to prolonged reductive and acidic conditions.

Metal chalcogenide coordination polymers as catalysts for the hydrogen evolution reaction

253rd National Meeting (2017)

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