(2ey) Builiding Nanomaterials for Energy Conversion and Energy Storage

At a very small-scale regime (< 10 nm), the properties of materials strongly depend on the size, shape, and surface of the crystals. The broad tunability of the properties at the nanoscale combined with an enhanced surface-to-volume ratio makes nanocrystals highly relevant to various applications ranging from optoelectronics to catalysis to medicinal chemistry.¹ However, nanocrystals often exhibit poor stability compared to bulk materials, thus, limiting their capabilities in all the applications mentioned above. Moreover, synthetic protocols have often been developed over the years through trial-and-error approaches. Thus, systematic strategies to control the size, shape, and composition of nanocrystals remain desired.

Overcoming the challenges described above requires a fundamental understanding of nanocrystal growth. In my future group, we seek to develop such knowledge and rationally design nanocrystal syntheses to obtain desired size, shape, stability, and composition. The primary focus will be on materials for energy storage, and energy conversion applications. My research interests include experimental investigation of reaction chemistry, nucleation and growth kinetics, growth mechanisms, and degradation pathways for nanocrystals to develop atomistic models. Furthermore, I am interested to explore the influence of different electrochemical environments on nanocrystal growth and develop new strategies to manipulate the nanocrystal structure. Finally, complementing the conventional approaches, our group will also use statistical and data-centric approaches for experimental design to develop data-driven models.

My doctoral work on growth of semiconductor nanocrystals and and postdoctoral work on developing physical and data-driven models for the durability of nanocrystal-based electrocatalysts are the perfect building block for my future group because they have provided me with a broad and deep scientific background to lead research in areas mentioned above.

Doctoral Research

My doctoral research focused on developing syntheses for colloidal semiconductor nanocrystals for optoelectronics and investigating their growth mechanisms. The primary focus of my doctoral dissertation was magic-sized semiconductor nanocrystals (MSNCs). MSNCs are very small (< 2 nm) nanocrystals with exceptional stability that grow in discrete steps jumping from one size to the next directly without forming intermediate crystallites.^2,5 Although MSNCs have been known for decades, the reason for their enhanced stability and growth mechanism remained a long-standing mystery. This was in part due to inability to synthesize large sizes and difficulty associated with their purification. We overcame this by developing a synthesis MSNCs of larger sizes (> 2nm). We then performed various growth experiments on isolated MSNCs and combined our insights with series of structural and optoelectronic characterizations. These experimental observations were further combined with an atomistic model based on classical nucleation theory and kinetic simulations based on the population-balance model to explain the growth of MSNCs. Finally, we exploited the findings from the model to modify the MSNCs growth trajectories leading to larger sizes and the development of protocols for novel materials and heterostructures. Besides obtaining fundamental insights on growth, newly developed MSNCs provided an excellent study system for evaluating the optical properties of semiconductors at the nanoscale, thus leading to a dedicated experimental investigation to determine their optoelectronic band structure.

Post-doctoral Research

My postdoctoral work focuses on combining in-situ characterization and data-driven analysis to enhance the performance of nanocrystal-based catalysts for fuel cells. The standard operation of electrochemical devices, like fuel cell, is preceded by an electrochemical pre-treatment or break-in or activation protocol. Such protocol activates the catalyst surface for the electrochemical operation of the cell. However, the influence of such a protocol on catalyst properties and performance remains poorly understood. In my work, we apply a design-of-experiments-based approach in combination with in-situ mass spectrometry to examine the activation of Pt nanocrystals supported on carbon (Pt/C) for electrocatalytic oxygen reduction reaction. Our setup provides valuable information about various degradation mechanisms that modulate the structure of the catalysts and, therefore, their final electrochemical performance. We combine our work with various ex-situ characterization techniques to identify different mechanisms. Finally, we explore strategies to integrate our experimental findings with data informatics model (e.g., causal inference graphs) to develop a holistic model for the stability of nanocrystal catalysts.

Teaching Interests

Good teachers or mentors have been central to my career development. Over the years, such teachers have made subjects more accessible, helped me gain a deeper understanding of the courses, and played a vital role in deciding my research direction. Consequently, I believe that teaching can shape students' careers and, thus, will be an important part of my job.

As a teacher, I plan to explore a student-centric approach comprising various active learning strategies that complement the passive content of the lectures. While the passive component would provide basic understanding for a subject, active components would enable the students to apply the knowledge and create knowledge in some cases. As a teaching assistant, I have included active components like think-pair-share exercises or project-based learning (e.g., comparing published data by performing experiments). Including such components will not only deepen the understanding of the subject but also develop the necessary soft skills required for their future jobs.

Given my educational background in chemical engineering, I am flexible to teach any course in chemical engineering. However, thermodynamics, electrochemistry, and mass transfer are most pertinent to my research. In addition, given the interdisciplinary nature of modern-day research and STEM careers, I would be particularly excited to develop or redesign courses to help chemical engineers transcend their field. Specifically, designing a course that includes the following concepts: i) quantum mechanics, ii) engineering nanocrystal growth and properties, and iii) electrocatalysis would be relevant for the students who plan to pursue careers in the energy and sustainability space. My educational training in chemical engineering, research in semiconductors, spectroscopy, and catalysis, and teaching experience in interdisciplinary courses like "Introduction of quantum mechanics for mechanical engineers" would be beneficial to develop such courses.

As a first-generation family member to travel abroad for higher studies, I strongly advocate for an inclusive environment for science. My background of working in international teams in various countries (India, Singapore, Switzerland, US) has provided me a first-hand experience of how diversity in cultures can generate and thrive some of the most vibrant research ideas. My previous experience has led me to be a part of the DEI committee in my current group where we regularly (every quarter) organize seminars to create awareness about the DEI issues in research and STEM careers. More importantly, we consistently seek feedback on our group culture and adapt our group policies to work towards an inclusive environment for all our group members.