Approximately half of the people on the planet are alive due to synthetically produced ammonia. However, due to the fossil fuels used in the current process, ammonia production contributes a significant amount to the world’s greenhouse gas emissions. By taking an electrochemically-based approach to this process, those emissions can be eliminated. However, current catalysts are not selective for the desired reaction. We hypothesize that 3D surface modifications can be utilized to overcome these limitations and create catalysts which mimic the selectivity of the nitrogenase enzyme, an enzyme that catalyzes the reduction of nitrogen to ammonia at mild temperatures and pressures. Therefore, in this study, peptide sequences have been designed to mimic the general function of the naturally-occurring nitrogenase enzyme. Recent results in an alkaline, solid-state electrochemical cell show promise using a synthetic peptide bound to iron(iii) oxide nanoparticles, which yield an electrochemical ammonia production rate that is 10x higher than the catalyst without bound peptide. Preliminary, repeated experiments in a liquid electrolyte cell at room temperature and atmospheric pressure illustrate similar promising results. Furthermore, gas adsorption isotherms suggest that this peptide does not significantly block nitrogen adsorption, and that the catalysts maintain the same surface area after binding to the peptides.

In addition, a simple and tunable peptide system has been designed to better understand how peptides influence electrochemical reactions. Emphasis is placed on understanding the hydrogen evolution reaction (HER) on Au, Fe₂O₃, and Pt metal surfaces, as HER is the main competing reaction for ammonia production. One of our main tools used to understand these peptide effects is a quartz crystal microbalance with dissipation (QCM-D), which is utilized in combination with an electrochemistry module (QEM) and humidity module to give real-time electrochemical and surface information. Importantly, the QCM-D is sensitive enough to measure the mass loading of the peptide on metal surfaces. Furthermore, the humidity module allows us to study the peptides’ effects on water uptake, which will also be useful for understanding HER in a basic environment, as water is the proton source. For instance, preliminary results show that at least one tripeptide species has a significant hydrophilic effect on water uptake when used on an Au sensor. Overall, these data are anticipated to influence general guidelines when designing selective catalysts for electrochemical reactions.