Oxygen Electrocatalysts of Ni/Fe-based MOF and Alloys via Combinatorial Material Approach

The Anion Exchange Membrane water electrolysis (AEMEL) has recently been regarded as a promising water electrolyser for producing hydrogen. It shares an identical characteristic of Alkaline Water Electrolyser (AEL) but with the additional advantage of higher operational current densities thanks to AEMEL's lower Ohmic resistance. On the other hand, compared with Proton Exchange Membrane Water Electrolyzer (PEMEL), the AEMEL does not require critical materials of Pt-based cathode, titanium electrode, rare-earth-based Ir and Ru-oxide anodes. In addition, PEMEL currently leans on fluorine-based polymer membrane, with a strong environmental impact because of the fluorocarbon gas emissions at the tetrafluoroethylene processing stage. In contrast to PEMEL, most of the development of membranes for AEMEL does not use fluorine.

Nonetheless, the technological maturity of AEMEL is still under development and commercially available AEMEL has not been launched in the market due to its lower performance compared with more established technologies of AEL and PEMEL. Most of the materials used for AEMEL today have been adopted from PEMEL and/or AEL, and not specifically designed for AEMEL. There is still no consensus on the state-of-the-art materials encompassing the AEMEL (e.g. catalysts, etc.), leaving a wide opportunity for further research and development.

At the heart of the AEMEL are the electrocatalysts where the water splitting into H₂ and O₂ gases takes place. The electrocatalysts do not consist of precious, rare or noble elements, which makes AEMEL attractive. The water electrolysis can be carried out using Ni-alloy electrocatalysts for both H₂ and O₂ gas evolution reactions, with some modifications to adapt to the favourable gas product. For instance, Ni-alloy electrocatalyst has already been used for H₂ evolution reaction, while Ni-Fe-Co alloy has been employed as a catalyst for O₂ evolution.

The major challenge in AEMEL operation is the sluggish O₂ evolution reaction on the surface of the anode, leading to the lower water electrolysis efficiency in comparison to AEL and PEMEL. The state-of-the-art Ni-Fe alloy anode may need to be enhanced further or substituted to boost the O₂ evolution reaction rate and thus improve the AEMEL performance.

Project Goals

The project goal is to investigate and to develop an O₂ electrocatalyst consisting of novel MOFs-based and MOFs-supported/mixed/functionalized NI alloy electrocatalysts towards AEMEL with low capital and operational costs, high performance, high durability, and low environmental impact. OxyCAT expects an AEMEL device with Ni-based and/or MOF-based electrocatalyst demonstrating the following characteristics:

1. Current density: more than 10 mA/cm² at 1.8 Volt
2. Overpotential: 200 – 400 mV.
3. KOH and/or K₂CO₃ concentration of 0.1 M at 60 °C temperature.
4. Ni alloy with a different alloying element and composition, determined by the combinatorial material method.

Innovations

Increasing the O₂ evolution reaction rate may relate to the materials issue, for instance, the non-optimized of Ni-alloy electrocatalyst composition to promote a high O₂ reaction rate. Another issue can also be the incorrect choice of the alloying elements or surface area of anode, which needs to be enhanced, either with nanostructuring or using new materials exhibiting high surface area and catalytic properties, such as Metaö-Organic Frameworks (MOFs). Therefore, a set of innovative investigations to overcome the abovementioned challenge is proposed:

1. Employing a new class of O₂ electrocatalyst based on Metal-Organic Frameworks (MOFs) and derivatives as anode in AEMEL.
2. Preparing a set of Ni alloys with various alloying elements, mostly transition metals, which will be done by combinatorial material electrochemical deposition of NI with alloying elements of Ce, Co, Cr, Fe, Zn, Mo and Sn.
3. Functionalizing or mixing the state-of-the-art NI alloy electrocatalyst with MOFs.
4. Direct MOFs growth on NI alloy.
5. Preparing a mixture of membrane and electrocatalyst (Ni-Fe alloy and/or MOFs) in the AEMEL device fabrication/ assembling.

Role of the AIT

Project partner and development of Ni-based layered double hydroxide (LDH) by high-throughput processing of combinatorial electrochemical deposition for anode/oxygen evolution reaction catalyst.

Project results

Funding