Using X-ray diffraction to characterize nanocatalysts.

Author: Jonathan Batey | Major: Chemistry | Semester: Spring 2025

During the spring semester of my junior year, I have been working with Dr. Jingyi Chen to synthesize nickel-iron hollow nanoshells to be used in the oxygen evolution reaction. The oxygen evolution reaction (OER) is one of the half reactions in water electrolysis, the other being the hydrogen evolution reaction (HER). Water electrolysis, also known as water splitting, is an electrochemical process that divides water into hydrogen and oxygen gas. Because water electrolysis can be accomplished using renewable energy sources and it emits only water, it is an attractive alternative for the generation of hydrogen in place of fossil fuels. However, a four-electron transfer in OER causes water electrolysis to be slow, limiting its use on an industrial scale. Catalysts are used to speed up the reaction, but many catalysts rely on rare-earth metals which are expensive. This makes water electrolysis too expensive to compete with the generation of hydrogen using fossil fuels. My project has focused on lowering the cost and improving the efficiency of water electrolysis using earth-abundant metal catalysts, specifically nickel and iron, so that water electrolysis can become a more viable solution for large-scale hydrogen production.

My project started like most do, reading literature to learn about my topic. During this phase of my project, I learned that a lot of research has already been conducted on earth-abundant metals as catalysts in OER like copper, iron, nickel, and cobalt. Of these abundant metals, nickel-iron nanoparticles’ electroactivity was similar to more expensive catalysts already employed in the reaction. Since I was new to reading scientific literature, Dr. Chen helped me extensively during this phase of the project. She recommended journals to look at, papers to read, and gave explanations when I read something I did not understand. So, after learning about water electrolysis and nickel-iron nanoparticles, we set out to improve the catalytic efficiency of these particles.

One method to improve the efficiency of most catalysts is to increase their surface area. When the surface area is increased, so is the amount of contact the catalyst has with the reagents, leading to an increase in efficiency. To do this, we aimed to make hollow nickel-iron nanoshells. First, I needed some sort of core that could act like a template for the formation of the nickel-iron nanoshell and could easily be dissolved to leave the nanoshells hollow. We decided that a copper core could work well since it could be easily dissolved with ammonium hydroxide. So, I first learned to synthesize copper nanoparticles (CuNP). Luckily, the Chen lab has already established a method for this synthesis, so David, Mei, and Deborah (all graduate students in the Chen lab) were able to teach me the synthesis. Next, I needed to coat my CuNP with nickel-iron. To begin with, I first focused on coating the CuNP with just iron to find the correct copper to iron ratio and establish a synthesis method. I synthesized CuNP using the Chen lab method and prepared them for the deposition of iron on their surface. I put them through a heating program to control how the solution was brought to and held at specific temperatures, then introduced an iron precursor to initiate deposition. My first few attempts were unsuccessful. The iron did not deposit on the CuNP and instead made iron nanoparticles. So, I had to slowly change one variable at a time to find success. I tried changing the amount of iron I added, the heating time, and the time the solution sat at a certain temperature. I was eventually able to find success and made copper nanoparticles with an iron shell. David also helped me during this phase of the project as he has done something similar with nickel phosphide particles. Next, I needed to etch the copper core to make hollow nanoshells which I accomplished by dissolving the copper in ammonium hydroxide.

In the next phase, I will apply the hollow iron nanoshells to OER to find their electroactivity and learn how to operate the electrochemical cell. Then, I will start to incorporate nickel in the coating procedure to make CuNP with a nickel-iron shell and eventually hollow nickel-iron nanoshells. Throughout my project I have discovered the joys of research. It fascinates me that small, minute changes I apply can affect the shape and size of materials so tiny you need an electron microscope to see. I now strive to one day have a research lab of my own focused on sustainable nanomaterials.