Scientists at Rice University in the United States are exploring ways to improve the cost-effectiveness of fuel cells by optimizing cathode nanomaterials and explain the atomic-level mechanism of the catalytic oxygen reduction reaction (ORR) of doped nanomaterials. Carbon nanotubes (CNTs) or modified graphene nanoribbons can be a viable alternative to platinum for rapid oxygen reduction, converting chemical energy into electrical energy, a process that is the main reaction of fuel cells.
In order to obtain the best performance of the oxygen reduction reaction, the different carbon materials obtained by different doping methods are shown in the figure: gray is carbon, pink is boron, blue is nitrogen and white is hydrogen.
Due to their good conductivity and mechanical properties, high-performance, well-engineered carbon materials are the key to oxygen reduction reactions, as researcher Xiaolong Zou said in 'Today Materials':' Developing Cathodic Redox The efficient catalyst in the reaction is crucial for large-scale applications of proton exchange membrane fuel cells. "According to the Nanoscale magazine 'Zou et. Al. Nanoscale (2017) DOI: 10.1039 / C7NR08061A', by using computer simulation, the research team The reason why the graphene nanoribbons and the nitrogen / boron-doped carbon nanotubes react too slowly and how to improve the problem has been studied.
Conductive nanotubes or doped nanoribbons change their chemical bond properties, which helps them to be used as cathodes in proton exchange membrane fuel cells In a standard fuel cell, the anode is charged with a hydrogen fuel and then separated into protons and Electrons. As negative electrons flow out as available current, protons are pulled into the cathode and recombine with electrons and oxygen to form water.
It has been found that nitrogen-doped ultra-thin carbon nanotubes can work most efficiently because of the interaction between dopants and the deformation of chemical bonds Nanotubes are better than nanoribbons in this regard because their curvature distorts The edges of the chemical bonds make it easier to bond, and they found that ultra-thin nanotubes with radii between 7 and 10 angstroms are ideal.
The development of efficient catalysts for cathodic oxygen reduction reactions is crucial for the large-scale application of proton exchange membrane fuel cells. - Xiaolong Zou
It has also been demonstrated that graphene nanoribbons with rich edges, nitrogen and boron doped, show comparable performance to oxygen-absorbing nanotubes. Here oxygen provides the opportunity to form double bonds because they can be directly connected to positively charged The boron doping sites. As Boris Yakobson said: 'Although doped nanotubes show good prospects, the substitution of nitrogen at the serrated edge of the nanoribbon can expose the so-called pyridine nitrogen (which has a known catalytic activity), therefore It is possible to achieve the best performance.
Now, the team hopes to develop new ways to study nano-scale electrochemical processes in real time and better perform interactions between dopants and defective carbon materials to improve performance.
