A bimetallic Nickel Iron layered double hydroxide system is sufficient for efficient O₂ production through water splitting, according to a new study that obviates the necessity of current trends of research to find trimetallic solutions for increasing productivity in this system.

In an era where renewable energy sources are gaining paramount importance, water splitting emerges as a beacon of hope in the quest for sustainable energy solutions. Water splitting can be reckoned as a sustainable and eco-friendly way to generate green and pure H₂ and O₂ on a larger scale without harming the flora and fauna.

To explore ways of increasing the efficiency of water splitting, scientists from the Institute of Advanced Study in Science and Technology (IASST) under the Department of Science and Technology (DST), Government of India, in Guwahati, have assessed one of the two important reactions that come into play -- hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER).

The work led by Dr. Biswajit Choudhury and the main author Mr. Suvankar Deka focused on the understanding of the oxygen evolution ability of Nickel-Iron Layered double hydroxides. This is because improving the efficiency of the OER contributes to the overall efficiency of water-splitting processes.

In addition to NiFe Layered Double Hydroxide (LDH), they synthesized two other trimetallic systems ZnNiFe layered double hydroxide and CoNiFe LDH, and investigated its electrocatalytic activity in 1M KOH. Strikingly, the OER activity of the trimetallic systems was found to be slower than the bimetallic system. The research provided mechanistic Insights into electrocatalytically reduced OER performance in marigold-like trimetallic NiFe-based LDH.

Their investigation accepted for publication in the Journal of Materials Chemistry A, revealed that the reduced activity in the trimetallic system can be attributed to breakage in the charge transfer chain of Ni-O-Fe-O-Zn and Ni-O-Fe-O-Co moieties (part of a molecule) as well as confinement of phonons (quantum of vibrational energy). This leads to the trapping of charge carriers affecting the reaction pathway and kinetics resulting in reduced water oxidation activity.

The study suggests that doping of the bimetallic NiFe system does not improve its water splitting efficiency and can help in focussed research on finding ways of improving the bimetallic system for oxygen generation through overall splitting.  

Publication link: https://doi.org/10.1039/D3TA07489G

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