Highly efficient catalysts of Ruthenium clusters on Fe3O4/MWCNTs for hydrogen evolution reaction

“Highly Efficient Catalysts of Ruthenium Clusters on Fe3O4/MWCNTs for Hydrogen Evolution Reaction” is the latest paper published by Prof Ranjit Thapa, Professor of Physics at SRM university-AP and his PhD scholar, Mr Samadhan Kapse, in ‘New Journal of Chemistry’ having an Impact Factor of 3.591.

In this work, the chemical co-precipitation technique is adopted to produce Fe3O4 nanoparticles under an inert atmosphere and was utilized for HER studies. The Ru nanoparticles were profitably deposited over Fe3O4/MWCNTs GC electrode using electrochemical deposition technique. The superior HER activity was achieved on Ru/Fe3O4/MWCNTs in 0.1 M H2SO4 aqueous media. We have demonstrated that the synthesized electrocatalyst offers a low overpotential of 101 mV to achieve a current density of 10 mA cm-2 towards the hydrogen evolution reaction. It displays long-term durability, exceptional cyclic stability even after 1000 cycles. DFT calculations imply that the availability of both octahedral and tetrahedral sites in Ru/Fe3O4/MWCNTs with low overpotential is more efficient towards HER. It is emphasized that a low percentage of ruthenium in the prepared catalyst can be substituted as a promising HER catalyst for sustainable energy technologies.

Abstract of the paper

Producing molecular hydrogen (H2) using water provides a sustainable approach for developing clean energy technologies. Herein, we report highly active ruthenium clusters (Ru) supported on iron oxide (Ru/Fe3O4) and Fe3O4/multi-walled carbon nanotubes (Ru/Fe3O4/MWCNTs) by simple electrochemical deposition in a neutral aqueous medium. The supported catalyst exhibits good hydrogen evolution reaction activity (HER) in an acidic environment. Cyclic voltammograms (CV) in potassium ferrocyanide (K4[Fe(CN)6]) confirm MWCNTs enhance the electron transfer process by decreasing the redox formal potential. The overpotential of Ru/Fe3O4/MWCNTs and Ru/Fe3O4 electrocatalysts versus reversible hydrogen electrode (RHE) was found to be 101 mV and 306 mV to reach a current density of 10 mA cm-2 . As prepared, the catalyst displays good stability and retain its HER activity even after 1000 cycles. Further, the stability of Ru/Fe3O4/MWCNTs was studied using chronopotentiometric (CP) technique for 12 hrs and found negligible loss in the catalytic activity towards HER. To explore the role of Ru and underneath MWCNTs to improve the catalytic performance of Fe3O4, density functional theory (DFT) calculations were carried out. DFT calculations indicate the octahedral site of Ru/Fe3O4 favours HER with low overpotential. However, Ru/Fe3O4/MWCNTs is more efficient towards HER could be due to the availability of both octahedral and tetrahedral catalytic sites.

Social implications of the research

Renewable energy generation is of greater importance in the present circumstances. This is caused by the depletion of non-renewable energy sources like fossil fuels and other hydrocarbon deposits and the release of greenhouse gases into the atmosphere. Hydrogen has gained considerable interest as an energy storage and energy carrier because of its high energy density (146kJ/g). Furthermore, its lightweight, profusion nature and the release of water during its combustion eliminate environmental pollution and thus contribute to defeating the global energy crisis. Also, hydrogen is an important and ideal energy source to develop fuel cells. A number of methods have been explored to generate molecular hydrogen. Among them, water electrolysis is a promising technology for generating high-purity hydrogen from water. An excellent electrocatalyst is obligatory to liberate hydrogen gas effectively from water. A higher HER activity is known to be obtained from platinum (Pt) and Pt-based catalysts. Given its high cost and low surplus, it limits expansion to the industrial scale. Over the few past decades, lots of efforts have been made by many research teams to find out alternative catalysts to substitute Pt electrodes.

The paper is published in collaboration with Shwetha Kolathur Ramachandra, Doddahalli Hanumantharayudu Nagaraju, and Shivanna Marappa; School of Applied Sciences, REVA University, Bangalore-560064, Karnataka, India. According to the research group, the density functional theory can boost the searching process of highly promising electrocatalysts for hydrogen evolution reactions in renewable energy generation.

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