Capturing reality through theoretical electrochemistry

21 April 2020

Yan Choi Lam (Croucher Fellowship 2016) is building a theoretical model to explain why certain chemical reactions happen the way they do. Specifically, he is examining how hydrogen is produced.

“I’m working on a theory that tries to explain how hydrogen is produced electrochemically,” said Lam, who is carrying out such work as a member of the Hammes-Schiffer research group in the Department of Chemistry at Yale University.

“If you pass electricity through a solution of water containing salt and acid, you get hydrogen at the cathode (the reduction electrode), and I want to know how that reaction takes place.”

Known as a hydrogen evolution reaction, it is a process whereby a water molecule – made up of two hydrogen atoms and one oxygen atom – is split into these components by an electric current. “This is a reaction that people would really love to be able to do more quickly,” Lam explained.

Hydrogen has a multitude of industrial uses. It is needed to hydrogenate fat and to produce ammonia for fertilisers, while its liquid form combines with liquid oxygen to create rocket fuel.

But Lam’s work is purely theoretical, so the scientist will not be getting singed by rocket exhaust anytime soon.

This is just how he likes it. “As a theoretical chemist, I use computers and theories to try to understand chemical reactions,” Lam said. “We want to know why certain reactions behave the way they do, in terms of how fast they are or how slow they are.”

Born in Hong Kong, Lam completed his secondary education in Singapore before earning his Bachelor of Science degree at Massachusetts Institute of Technology (MIT). He undertook his doctoral studies and initial postdoctoral research at California Institute of Technology (CalTech) and after eight years returned to the east coast to work at Yale.

Lam’s theories must correctly describe the relationship between different parameters of the reaction, such as electrode potential and reaction rate. “If you change the electrode potential, the rate of reaction changes,” Lam said. “The reaction becomes faster as you make the electrode more negatively charged.

“The relationship between electric potential and rate of reaction can be explained even by fairly crude theories that might be wrong in other respects,” he cautioned.

To judge the accuracy of possible theories, the scientist and his colleagues rely on the kinetic isotope effect as well. “This effect is a good indication of whether our theory is actually a good one because it is quite sensitive to the theoretical models we use to calculate it,” Lam explained.

The effect occurs when an atom is replaced by one of its isotopes during a reaction. The atoms of each element – the building blocks of all matter on earth – have unique numbers of protons – positively charged sub-atomic particles – in their core. For instance, every atom of oxygen has eight protons while each atom of hydrogen has one.

While the number of protons remains constant, the number of neutrons can differ, creating isotopes of an element. When an atom is replaced by an isotope during a reaction, the subsequent change in the rate of reaction is known as the kinetic isotope effect.

If a theory’s predicted kinetic isotope effect is correct, this suggests the scientist is on the right track. “Ideally, the model that we’ve developed is able to explain both the relationship between the electrode potential and the rate constant and also the kinetic isotope effects,” Lam said.

The complexities of theoretical electrochemistry that Lam deals with on a daily basis are a far cry from what drew him to the field. “What got me into chemistry initially was the process of colour change,” Lam explained.

Watching colour change occur during a chemical reaction is one thing; understanding how it happens is something else.

“Some reactions have been known experimentally for 100 years and people are still debating how to understand certain observed phenomena,” Lam noted. “So despite the fact that we know how to do an experiment, we often still don't have a very solid grasp of how it works.”

Lam hopes to get a firmer grip on the reactions he studies. “All models are wrong, but some are useful,” he said. “This is because every model misses a part of reality, but some capture enough of reality to make them useful to us.”

The scientist plans on capturing as much of reality as possible.

Dr Yan Choi Lam earned his Bachelor of Science in Chemistry at Massachusetts Institute of Technology and a PhD at California Institute of Technology, with his thesis covering inorganic synthesis and catalysis, spectroscopy and photophysics, as well as computational studies of catalytic mechanisms. He is currently a postdoctoral associate in the Hammes-Schiffer research group in the Department of Chemistry at Yale University, where he is exploring and modeling Proton-Coupled Electron Transfers (PCET) at electrode-electrolyte interfaces. Dr Lam received his Croucher Fellowship in 2016.

To view Lam’s Croucher profile, please click here.