In one of the major breakthroughs, researchers have found out that adding caffeine to the electrodes can go on to enhance the ORR activity of platinum electrodes by 11 times. This kind of exploration can go on to enhance the efficiency of the fuel cell, decrease the need for excess platinum catalysts, and thereby lead to cheaper as well as more efficient fuel cells.
With worldwide goals set in terms of transitioning away from the path of fossil fuels, fuel cells indeed stand out as one of the very promising carbon-free energy sources.
Comprising an anode as well as a cathode, which happen to be separated by an electrolyte, fuel cells go on to convert the chemical energy of fuel directly into electricity. The anode gets the fuel, whereas an oxidant, majorly oxygen from the air, gets introduced at the cathode. In a hydrogen fuel cell, hydrogen goes through oxidation at the anode, thereby producing hydrogen ions as well as electrons. The ions go through the electrolyte to the cathode, and hence the electrons flow via an external circuit, thereby generating electricity. At the cathode, oxygen blends with the hydrogen ions as well as electrons, thereby resulting in water as the only byproduct.
But the presence of water goes on to affect the performance of fuel cells. It reacts with the platinum-Pt catalyst, thereby forming a layer of platinum hydroxide- PtOH on the electrode, which then obstructs the efficient catalysis of the oxygen reduction reaction- ORR, thereby leading to energy losses. So as to maintain efficient operations, fuel cells need a high Pt loading, which goes on to prominently raise the costs of fuel cells.
At present, in a study that’s published in the journal Communications Chemistry on February 3, 2024, Professor Nagahiro Hoshi as well as Masashi Nakamura, Rui Suzuki, and Ryuta Kubo, all from the Graduate School of Engineering, Chiba University, Japan, have gone ahead and found that adding caffeine to specific platinum electrodes can go on to increase the activity of the ORR. This exploration happens to have the potential to decrease the platinum requirements, thereby making the fuel cells more affordable as well as more efficient.
According to Professor Hoshi, caffeine, which is one of the chemicals contained in coffee, goes on to enhance the activity of a fuel cell reaction 11-times on a well-defined Pt electrode in which the atomic arrangement happens to have a hexagonal structure.
In order to evaluate caffeine’s effect on the ORR, researchers went ahead and measured the current flow by way of platinum electrodes, that were immersed in an electrolyte which contained caffeine. These platinum electrodes happened to have surface atoms that were arranged in specific directions, called (111), (110), and (100). There did happen to be some notable improvement in the electrode’s ORR activity with a rise in caffeine concentration in the electrolyte. It is well to be noted that caffeine, when present, goes ahead and adsorbs onto the electrode’s surface, thereby efficiently safeguarding the hydrogen adsorption as well as the formation of Pt oxide on the electrode.
But the effect of caffeine depended on the orientation of platinum atoms on the surface of the electrode.
Interestingly, at a caffeine molar concentration of 1 × 10−6, ORR activity on Pt(111) as well as Pt(110) surged by 11 and 2.5 times, respectively, having no noticeable effect on Pt(100). So as to understand this difference, researchers went deep into the molecular orientation of caffeine on the electrode surface by way of using Infrared Reflection Absorption Spectroscopy. They ascertained that caffeine gets absorbed on Pt(111) as well as Pt(110) surfaces due to its molecular plane, which is perpendicular to the surface. But, on Pt(100), steric hindrances compel it to get attached to its molecular plane, which is tilted relative to the surface of the electrode.
Professor Hoshi adds that the increased ORR activity of Pt(111) as well as Pt(110) was attributed to reduced PtOH coverage along with lower steric hindrance of the adsorbed caffeine. Conversely, when it came to Pt(100), the impact of reducing PtOH was counteracted by way of steric hindrance pertaining to the adsorbed caffeine, and hence caffeine did not go on to affect the ORR activity.
It is worth noting that unlike batteries, having limited lifespans, fuel cells can go ahead and generate power as long as the fuel is supplied, thereby making them suitable for numerous applications such as vehicles, buildings, as well as space missions. This proposed method happens to have the potential to enhance the designs of fuel cells as well as lead to their broadened usage.
