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Highly Efficient and Sustained Electrochemical Hydrogen Evolution by Embedded Pd-Nanoparticles on a Coordination PolymerReduced Graphene Oxide Composite

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journal contribution
posted on 22.10.2019, 18:45 by Chandraraj Alex, Sachin A. Bhat, Neena S. John, C. V. Yelamaggad
The eventual specific use of an electrocatalyst for the hydrogen evolution reaction (HER) largely depends on its durability (robustness), ability to maximally lower the over potential of an electrochemical reaction, and cost of synthesis (production). Presently, there have been some strategic and promising demonstrations where coordination polymers (COPs)/metal organic frameworks have been explored as alternative candidates for the development of stable electrocatalysts capable of attending to two important parameters: the over potential and Tafel slope. Working in this direction, herein we report on the facile preparation, characterization, and excellent HER activity of a robust and cost-effective electrocatalyst. This catalyst, obtained by partially reducing a composite of COP and reduced graphene oxide (rGO) resulting from the reaction of 1,2,4,5-benzenetetramine (BTA) ligand with palladium­(II) chloride (PdCl2) in the presence of rGO, labeled as [Pd­(BTA)-rGO]red, exhibits a remarkable overpotential of −127 mV at −10 mA/cm2 current density featuring a Tafel slope of 55 mV/dec with high durability of 70 h at −300 mA/cm2. The analogous materials such as Pd­(BTA), Pd­(BTA)-rGO, Pd-rGO, and [Pd­(BTA)]red, when probed in comparison, utterly defer in rending the aforementioned activity. The extensive experimental investigations show that the Pd nanoparticles of size ∼3–5 nm embedded in the composite 2D sheets/layers are the root cause for the remarkable electrocatalytic activity of [Pd­(BTA)-rGO]red. A combination of high activity due to Pd nanoparticles, less charge transfer resistance due to rGO, and above all, stability due to encapsulation of Pd nanoparticles by 2D sheets of Pd­(BTA) and rGO works in favor of the high efficiency and durability of the material.