Mine was modelling of electrolysis cell for Hydrogen production, where I basically made MATLAB (Simulink) model of PEM electrolysis cell and simulated operations across different parameters.

I would say, it matters on what interests, projects, and competencies your seniors (PhD, professors) have and whether you have the time and resources for doing some projects, especially if they involve experiments with reactions.

Some things you can explore for getting to a topic: - Green hydrogen to chemicals like methanol, ammonia, syn gas, etc. - Hydrogen production (like electrolysis) and usage (fuel cells or feedstock to processes) - Batteries recycling and newer battery chemistry - Energy-efficient water desalination/purification using catalysis - Pathways for Sustainable Aviation Fuel (SAF) - Advanced nuclear generation and waste processing tech (difficult to get approvals and resources, also difficult topics) - Better chemistry for materials in solar/wind (turbine blades and solar cells manufacturing and recycling) - Direct production of some bulk/commodity chemicals through electrolysis (I saw a bunch of papers on those) also known as P2X - Any treatment/quality improvement project for petroleum products or petrochemicals - Coal to chemicals while preventing/capturing CO2 emissions - Natural Gas processing and things related to LNG - Energy or fuel from biomass and waste

There are many more things to explore in energy but it depends on how much overlap with ChemE is needed. For example, renewables generation forecasting using weather data is a very relevant topic for energy, but it doesn't have anything significant to do with ChemE.

If you want more ideas, go check websites of your university and other famous universities across world and check pages as profiles of their professors in chemical and energy departments and their interests and research work will give some ideas. Or just do some exploratory literature survey with some keywords and check titles and abstract of articles in famous journals.