Characterization of Ni-Mo based electrocatalysts for hydrogen evolution from water
One of the greatest challenges of our society is decreasing our dependency of fossil-derived energy by replacing it – at least partially - with renewable energy. There are various sources of alternative energy, such as wind and solar energy. A downside of most of these alternative energy sources is that the energy is mostly harvested is the form of electricity, which is hard to store cheaply on longer terms. Storage of the energy is necessary because most alternative sources do not yield energy continuously, for example due to the day-night cycle of the sun.
A proposed solution to the electricity storage problem is to store the energy chemically. The hydrogen-hydrogen bond is known as one of the most energy-rich bonds and can be obtained using water splitting. Water splitting can be done directly for example using sunlight through photocatalysis, or indirectly through electrocatalysis using any electricity generating alternative source.
In this research, Ni-Mo based electrocatalysts will be studied for the hydrogen evolution reaction from the overall water splitting reaction. Metallic Ni-Mo alloys have been reported to generate hydrogen almost as efficiently as Pt in alkaline solutions. The current density is in the order of 10 mA/cm2. This order of magnitude of current density is normally yielded by solar panels. However, in many cases the Ni-Mo changes when running for a long time.
In this project, the Ni-Mo catalyst materials will be studied in terms of morphology, phase, composition and performance to investigate the possible changes Ni-Mo undergoes during hydrogen evolution. The main synthesis method of Ni-Mo will be electrodeposition. Electrodeposition is often the method of choice for electrocatalysts, because the obtained films are guaranteed to have a good electrical contact with the substrate when obtained.
The focus of the research will be on the effect of changing the synthesis parameters, and the operating potential and time of the hydrogen evolution reaction. Information on the morphology and local composition will be obtained using SEM-EDX, while the overall composition will be determined using AAS. XPS and other X-ray based techniques, such as XANES and EXAFS, will be used to study the phase of the alloy. Lastly electrochemistry itself will be used to check the performance, GC could potentially be used to check the Faradaic efficiency of the hydrogen evolution.
Finally it will be attempted to improve the catalyst based on the results obtained from the earlier parts of this research. Electrodeposition is a versatile method since stirring speed, deposition current and bath composition can all be varied to change the composition and morphology of the deposition. This property will be used to find a way of obtaining more stable Ni-Mo electrocatalysts. On the other hand, it is also possible to introduce other metals such as Fe or Co, or functionalise the catalyst with for example C, P, N or S, as some claims have already been made that this might stabilise the Ni-Mo catalyst material.