Researchers from the Centre for Nano and Soft Matter Sciences (CeNS), under the Department of Science and Technology (DST), Government of India, have developed a novel palladium-based electrocatalyst for hydrogen production that exhibits high catalytic efficiency with a low overpotential and high durability. The catalyst realized is basically a partially reduced composite of coordination polymer and reduced graphene oxide (COP-rGO composite).

The future of hydrogen as a fuel lies in the design of efficient electrocatalysts for electrochemical splitting of water to produce hydrogen. The commercially used Platinum (Pt)/Carbon (C) catalysts are efficient but expensive and suffer from metal ion leaching or electrocatalyst corrosion when used for long duration.

“The catalyst required an extremely low overpotential of -127 mV to achieve a current density of -10 mA/cm2 with a Tafel slope of 55 mV/dec. It also exhibited exceptionally high durability for 70 hours at a high current density of −300 mA/cm2,” the researchers said.

In their work, the researchers said the partially reduced COP-rGO composite can be readily synthesized by the reaction of 1,2,4,5-benzenetetramine (BTA) ligand with palladium (II) chloride (PdCl2) in the presence of rGO, and is therefore labelled as [Pd(BTA)-rGO]red.

The presence of organic ligand, BTA, with four primary amine groups, aids in forming 2D COP sheets with Pd2+ ions.

BTA is also capable of stabilizing the Pd nanoparticles formed during partial reduction without complete collapse of the 2D framework of COP. The rGO improved the conductivity of Pd(BTA) by facilitating the interaction between the 2D COP and rGO.

The researchers attribute the remarkable electrocatalytic activity of [Pd(BTA)-rGO]red to the Pd nanoparticles of size 3-5 nm embedded in the composite 2D sheets/layers.

“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,” they stated in their report.

“Developing efficient means of splitting water to produce hydrogen and obtaining the energy required for it from solar energy would be a significant part of the sustainable and green solutions for our energy needs,” said Prof Ashutosh Sharma, Secretary, DST.