Researchers from the University of North Texas, Case Western Reserve University, and Ulsan National Institute of Science and Technology (UNIST) have developed a new and innovative method of devising low cost fuel cells. This has become possible by the utilization of edge-halogenated graphene nanoplatelets in the development of metal-free electrocatalysts.
Scientists have been working on the idea of using pure hydrogen for fuel requirements that will reduce the pollution (since the only by-product released as a result of fuel combustion will be water). However, the biggest limiting factor is cost of platinum (Pt) catalysts that are currently used in the fuel cell technologies. In addition, other cost limiting factors are sluggish oxygen reduction reaction (ORR) at cathode, poor long-term operation stability and carbon monoxide (CO) poisoning or methanol crossover effects seen with the use of platinum and its alloys in the fuel cell technology.
The latest work by researchers of University of North Texas and other institutes:
In lieu of high cost and decreased reproducibility of platinum, researchers have developed a cost-friendly, metal-free catalyst that can be easily produced according to industrial and commercial requirements. The researchers utilized ball-milling graphite flake in order to synthesize a series of edge-selective halogenated (Cl, Br and I – from chlorine (Cl2), bromine (Br2), or iodine (I2) respectively) in graphene nanoplatelets (XGnPs).
When researchers tested graphene nanoplatelets (XGnPs) as cathode electrodes of fuel cells, it was observed that the XGnPs can be used as a potential replacement of platinum (Pt). This is because XGnPs possess tremendous electrocatalytic activities for ORR. In addition the higher tolerance to methanol crossover/CO poisoning decreases the cost of production and increases the likelihood of commercialization. Lastly, XGnPs are more stable when compared to original graphite and commercial Pt/C electrocatalysts.
The leader of research team, Prof. Jong-Beom Baek of Ulsan National Institute of Science and Technology commented:
“Our result presents new insights and practical methods for designing edge-functionalized GnPs as high-performance metal-free ORR electrocatalysts through low-cost and scalable ball-milling techniques.”
Prof. Liming Dai of Case Western Reserve explained:
“We made metal-free catalysts using an affordable and scalable process. The catalysts are more stable than platinum catalysts and tolerate carbon monoxide poisoning and methanol crossover.”
About Edge-halogenated graphene nanoplatelets (XGnPs):
Edge-halogenated graphene nanoplatelets (XGnPs) are a preferred choice because of their high stability, high tolerance potential and electrocatalytic activity toward ORR. So far, all of the efforts that were made to build cost-effective, metal-based electrocatalysts proved insufficient due to a variety of factors including poor cycle stability, low electrocatalytic activity, and the risk of environmental pollution. Alternatively, metal-free and carbon-based catalysts that utilized varying proportions of phosphorus (P), sulfur (S), boron (B), halogen and nitrogen (N) are although popular but effectiveness is limited by the high cost of production at the industrial or commercial scale.
So far, Edge-halogenated graphene nanoplatelets (XGnPs) appear like a possible solution that can be prepared at affirfable rates and on a large scale on high speed rotation (500 rpm) of stainless steel ball mailing that produces tremendous kinetic energy to break C-C framework and allow halogens to fit in the sealed ball-mill capsule.