Title : S, N co-doped graphene quantum dots modified TiO2: an excellent electrocatalyst for oxygen reduction reaction
Energy security and environmental pollution are the two most discussed topics in recent times in the research community. Environmental degradation is a significant concern nowadays due to the extensive use of fossil fuels. Also, the depletion of fossil fuels is a matter of concern in energy demand in human society. Given these circumstances, there is an urgent need to develop clean and sustainable energy technology to solve the shortage of fossil fuel-based energy sources and environmental pollution. In this context, among the different energy conversation and storage technology, fuel cell and metal-air batteries have gained enormous interest in recent times. They are known for their high energy density, high efficiency, and clean operation. But the major bottleneck associated with these technologies is oxygen reduction reaction (ORR) which is known for its sluggish nature. Currently, Pt/C is the state of art catalyst for these technologies. But the high cost, catalyst stability, and durability are the primary concerns associated with Pt/C. So, there is extensive research that has been going to develop a durable, active, low-cost catalyst. This study reports S, N doped graphene quantum dot modified TiO2 supported with carbon (S, N-GQD/TiO2/C-800) as an excellent electrocatalyst for the oxygen reduction reaction. Even the prepared catalyst is purely nonprecious metal-based S, N-GQD/TiO2/C-800 is synthesized using a facile two-stage hydrothermal method. The catalyst shows an excellent electrocatalyst performance with an onset potential of 0.91 V vs. RHE and a half-wave potential of 0.82 V vs. RHE in an alkaline medium. The Tafel slope is 61 mV dec-1 indicates excellent kinetics of the catalyst. ORR happens on the catalyst surface close to the 4 e- transfer process with 20% H2O2 productions. The catalyst shows 80 % current retention for 15 h, which offers good stability of the catalyst. The catalyst S, N-GQD/TiO2/C-800 is also highly methanol tolerant. The enhanced ORR performance is attributed to the strong synergistic effect between S, N-GQD/TiO2, and carbon. Along with unique structure, formation helps to get high electrical conductivity, high surface area with desirable charge transfer across the interface of S, N-GQD, and TiO2.