Electrocatalysts can be powerful weapons in our battle against climate change: these chemical reaction accelerants are critical components in clean energy generators and energy storage devices. The unique chemical properties of electrocatalysts can bridge the divide between renewable energy sources (such as solar and wind power) and existing energy frameworks, thus easing our reliance on fossil fuels.
A kaleidoscope of metal and non-metal-based electrocatalysts, each with its own advantages and limitations, is available to chemical engineers. This has prompted efforts to characterise and optimise these chemicals to maximise their potency, specificity and stability for cost-efficient clean energy applications.
To this end, researchers in the field have held on to a long-standing belief that the smaller, the better—nanosized particles have larger surface areas, which equate to greater catalytic efficiencies. However, Ming-Yong Han, a Senior Scientist previously with A*STAR’s Institute of Materials Research and Engineering (IMRE) hypothesised that other factors are also at play in influencing the performance of electrocatalysts.
“It is not that easy to study,” noted Han, adding that smaller catalyst particles can have different surface structures which can fundamentally change the dynamics of chemical reactions at the electrocatalytic interface. Moreover, these nanosized structures can also have different stabilities, which also factor into their overall efficiency.
Together with researchers from Nanyang Technological University, Singapore, Han performed an in-depth review of the research landscape and explored reports on the size-function relationship of common electrocatalysts. They confirmed that in most cases, nanosizing electrocatalysts increases the surface area of the electrodes, thereby improving device performance. Beyond these engineering considerations, however, they also found that this miniaturising step had an impact on the fundamental science behind electrocatalytic reactions.
For instance, the size of platinum electrocatalysts significantly affects their performance in proton exchange membrane fuel cells; smaller particles actually exhibit lower intrinsic activity, with peak performance achieved in particles of about five nanometres in size. Therefore, deeply understanding these size-related effects is essential for optimising catalysts for specific electrochemical applications.
With their findings, the team proposed a framework for the systematic study of these largely elusive intrinsic effects as a means of minimising costs while maximising performance. The framework suggests various experimental techniques to quantify different catalysts and highlights the importance of more theoretical studies to drive progress in the field.
Looking to the future, Han hopes that this investigation will spur downstream research on scalable and cost-effective catalysts for a greener energy industry.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE).
