Engineering of Electrocatalysts for HER and Oer Using Carbon Cloth Combined with Nonprecious Metals
Authors: Dalla Benetta Marilia Barreto , Breslin Carmel B , Dempsey Eithne 
Published: December 2024

The energy production sector has faced many challenges, especially regarding the environmental impacts caused by the use of fossil fuels. Renewable hydrogen, generated via electrolysis of water, has emerged as a possible solution to reducing global reliance on fossil fuels as a source of energy. Unfortunately, the electrocatalysts used currently for water splitting are expensive and limited, therefore, development of commercially viable, new cost-effective electrocatalysts is required. Many emerging catalysts are made using hydrothermal synthesis, demonstrating good water-splitting performance. However, the methods used to make such materials can be time and energy consuming, while generating a significant quantity of chemical waste (solvent and nanoparticles), which remain in the environment for long periods. This study focuses on the development of an environmentally benign solvent-free, room temperature synthesis design taking advantage of abundant, low-cost materials.

In the first phase of this study, a novel one-pot room temperature reaction was identified for the facile modification of Ni-containing substrates. This involved a simple hydrolysis method realizing NiMoO4/NiS/Ni(OH)2 complexes formed on the surface of Nickel Foam. This newly developed catalyst demonstrated impressive OER activity under alkaline conditions, showing great potential as an alternative catalyst for water splitting. The electrochemically active surface area of the modified Nickel Foam was also investigated resulting in an impressive fold increase in surface area.

Nickel Foam in its own right is an effective catalyst for water splitting, making it challenging to discriminate the effectiveness of immobilised electrocatalysts. It is also a porous substrate which makes it challenging to accurately estimate its performance, and formation of oxides can result in false results and corrosion over time with nickel dissolution being of environmental concern. In order to address these issues, the second phase of the work employed carbon cloth as a substrate due to its attractive features of low cost, availability, porosity and lack of catalytic performance in the absence of modification.

A number of metals including copper, were electrodeposited on the carbon cloth and further modified by this novel one-pot room-temperature hydrolysis reaction, resulting in copper molybdate coated carbon cloth which presented a significant improvement relative to the bare substrate. Performance data realized good current density, impressive onset potentials, good Tafel slopes, low impedance, and good stability. The substrate’s performance regarding the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) were evaluated in alkaline electrolytes with the view to develop a novel bifunctional material prepared using a novel, efficient electroless deposition method. A comparison was made with respect to commercially available electrocatalysts, and hydrothermally prepared materials used currently for OER and HER with encouraging bifunctional data realized. The new room temperature electroless deposition method represents a solvent free, low temperature, facile approach which provides excellent coverage on the Ni Foam/carbon cloth surface. The method has resulted in a suite of viable candidates that can act as bifunctional materials for water splitting based on a green synthesis approach.

Fig 1: Schematic showing the proposed formation of NiMoO4/NiS/Ni(OH)2 at NF surface.

Figure 1