Arumugam Sivanantham

Inexpensive electrochemical synthesis of nickel iron sulphides on nickel foam: super active and ultra-durable electrocatalysts for alkaline electrolyte membrane water electrolysis

Efficient and durable electrocatalysts for water splitting (both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER)) are required for the replacement of expensive noble metal-based catalysts used in water electrolysis devices. Herein, we describe the inexpensive synthesis of electrochemically deposited nickel iron sulphides on nickel foam (NiFeS/NF) and their use as highly efficient bi-functional water splitting catalysts that can meet the current energy demands. The NiFeS/NF electrocatalysts exhibited low overpotentials of approximately 231 mV for the OER and 180 mV for the HER in 1 M KOH. Moreover, the NiFeS/NF electrocatalysts exhibited a turnover frequency of one order of magnitude higher than those of state-of-the-art noble metal catalysts (RuO2 and Pt/C) for the OER and HER. In addition to this excellent activity, the bi-functional catalyst also exhibited an outstanding OER and HER electrode stability for over 200 h with minimal loss in activity. Further, it can be directly used in the practical application of alkaline electrolyte membrane water electrolysis. The high performance, prolonged electrode stability, and facile synthesis as an adherent coating on nickel foam suggest that NiFeS/NF electrocatalysts might be suitable for use as alternative commercially viable catalysts.

Nanostructured Nickel-Cobalt-Titanium Alloy Grown on Titanium Substrate as Efficient Electrocatalyst for Alkaline Water Electrolysis

One of the important challenges in alkaline water electrolysis is to utilize a bifunctional catalyst for both hydrogen evolution (HER) and oxygen evolution (OER) reactions to increase the efficiency of water splitting devices for the long durable operations. Herein, nickel-cobalt-titanium (NCT) alloy is directly grown on a high corrosion resistance titanium foil by a simple, single, and rapid electrochemical deposition at room temperature. The electrocatalytic activity of NCT alloy electrodes is evaluated for both HER and OER in aqueous electrolyte. Our NCT electrocatalyst exhibits low overpotentials around 125 and 331 mV for HER and OER, respectively, in 1 M KOH. In addition to this outstanding activity, the bifunctional catalyst also exhibits excellent OER and HER electrode stability up to 150 h of continuous operation with a minimal loss in activity. Further, the NCT alloy directly grown on titanium foil is used to directly construct membrane electrode assembly (MEA) for alkaline electrolyte membrane (AEM) water electrolyzer, which make the practical applicability. This single-step electrodeposition reveals NCT on titanium foil with high activity and excellent electrode stability suitable for replacing alternative commercial viable catalyst for the alkaline water splitting.

CoS2–TiO2 hybrid nanostructures: efficient and durable bifunctional electrocatalysts for alkaline electrolyte membrane water electrolyzers

The development of efficient catalysts to overcome the significant overpotential of the oxygen evolution reaction (OER) is the key bottleneck in the large-scale production of pure hydrogen. In the present work, we describe a simple approach for the fabrication of CoS2–TiO2 hybrid catalysts by the heat treatment of a cobalt thiourea complex in the presence of TiO2. We show the CoS2–TiO2 hybrid as a bi-functional electrocatalyst for overall water splitting in alkaline electrolyte membrane water electrolyzers. The optimal CoS2–TiO2 hybrid offered low overpotentials of 231 and 198 mV for the OER and HER, respectively. Fundamental studies pertaining to the role of TiO2 in enhancing the catalytic activity of the materials using optical and electrochemical band gap measurements of the CoS2–TiO2 hybrids were carried out. Additionally, the constructed MEA using the CoS2–TiO2 hybrid showed higher performance with an approximately 234 mA cm−2 current density at a cell voltage of 1.9 V and exhibited extended durable operation over 200 h, as compared to the MEA constructed with state-of-the-art all-noble-metal electrodes.

Nanocarbons and Their Composite Materials as Electrocatalyst for Metal–Air Battery and Water Splitting

We discuss multiple advantages of nanocarbon and their composite materials in metal–air batteries and alkaline water electrolyzer due to their unique properties and structural integrity. In energy devices, the nanocarbon-based electrocatalysts play a significant role to decide the cell efficiency and their stability. As compared with nanocarbon, the nanocarbon composites with the transition metal, metal oxide, and/or metal chalcogenides/pnictides provide additional electrocatalytic active sites to enhance the cell performance. Overall, we have discussed the recent progress on various nanocarbon composites design, tuning of their unique properties, and pros and cons in advanced metal–air batteries and water electrolyzer.