Computational chemistry for clean energy applications
Professor Debra Bernhardt uses a range of theoretical and computational chemistry techniques to study and develop new materials for clean energy applications. From better catalysts for hydrogen fuel cells to more effective electrode and electrolyte materials for rechargeable batteries and supercapacitors, she is helping reduce the limitations of existing clean energy technologies.
Debra began her career in wave function quantum computation methods, and quickly developed an interest in using computational chemistry approaches to develop a fundamental understanding of the behaviour of matter. Through further study at the University of Basel in Switzerland and then at the Australian National University (ANU) she extended her computational expertise to molecular dynamics simulations and non-equilibrium statistical mechanics to study systems involving fluid flow.
Now with a joint appointment with the Australian Institute for Bioengineering and Nanotechnology and the School of Chemistry and Molecular Biosciences at the University of Queensland, she is combining her expertise in both quantum chemistry and molecular dynamics simulation in clean energy materials research, investigating the energy storage and transfer behaviour of materials at the atomic level.
What drew her to science?
“I always really enjoyed chemistry in high school,” admits Debra. “Particularly the laboratory experiments – I thought it was amazing to make different chemicals with different colours or smells, or that even gave off light. I was always curious to know why different chemicals behave the way they do.”
While she studied a broader range of physical sciences at university, it was the hands-on chemistry laboratories that ‘kept her coming back’. Debra remembers: “It’s ironic that I ended up being a theoretical chemist – I got busy with the theory and computation while I was waiting a long time for some experimental equipment to arrive for my PhD project, and never looked back.”
Research with supercomputers
“One of the advantages of doing chemistry on a computer is the control you can have on the molecular structure,” she explains. “In real physical experiments, your graphite electrode may not have a completely ordered structure, or the distribution and concentration of dopant metals may not be uniform. Using computation, we can make our samples very pure and structurally uniform, we can control the doping and crystalline defects. That allows us to get a much better understanding of exactly which factors affect the behaviour we observe in these materials experimentally.”
Computation and simulation is also one of the only ways to study systems while they’re operating without disturbing them. “You can’t watch a capacitor discharge directly, or see the ions diffuse between electrodes under an applied voltage, for example. So working on energy storage systems, you need input from both experiment and computation. You just get different information, and some of that operational information, from the calculations.”
“Supercomputing lets us do our calculations at even higher levels of theory, and on bigger systems – for example you can only look at electrode doping concentrations as low as one in a million if you’re simulating over a million atoms to start with. Faster computations also let us follow systems for longer periods of time, so we can see double layers form and discharge on capacitors, or the slow diffusion of charge carriers though very viscous ionic liquid electrolytes.”
Real world solutions
The challenge is to create better energy storage and transfer options for renewable energy sources.
“Looking at the binding energy of atoms to electrodes can tell us about a battery’s capacity, whereas measuring the diffusion coefficient or conductivity can tell us how fast we can charge and discharge it. If we see the material structure start to distort over several charge/discharge cycles, it corresponds to batteries that lose capacity and stop working over time, as their components irreversibly break down at the atomic level.”
Debra continues to be driven to solve problems and do things better, from developing new theories to predict outcomes of processes, to optimising computer code so her simulations at Pawsey run faster and using them to develop cheaper, more stable and more efficient materials for batteries and supercapacitors.