Influence of phosphorus-doped bilayer graphene configuration on the oxygen reduction reaction in acidic solution

Abstract

The challenges posed by global warming and climate change can be solved by utilizing alternative and renewable energy sources to provide efficient and ecofriendly energy for sustainable energy conversion. Fuel cells, especially polymer electrolyte membrane fuel cells (PEMFCs), can convert air pollution via chemical reactions to generate electricity and water and are considered next-generation technologies for the green economy. The oxygen reduction reaction (ORR) at the catalyst layer plays an important role in determining a fuel cell's price and electrochemical performance. Recently, non-platinum-group metals (non-PGMs) have emerged as promising low-cost and high-performance catalysts for PEMFCs. This study investigates the electronic properties and the electrocatalytic activity of a single P-doped monovacancy (PC3-BLG) and divacancy (PC4-BLG) of an AB-bilayer graphene in a sulfuric acid solution. The results show that the PC3-BLG exhibits greater stability and better electrocatalytic activity than the PC4-BLG. For the PC3-BLGs, an indirect energy gap of ∼0.46 eV is predicted, suggesting a transformation from a half-metallic to a small-bandgap semiconductor, whereas the PC4-BLG is predicted to be a p-type semiconductor. An activation energy of 0.54 eV was found for the PC3-BLG, where the rate-limiting step in the ORR is the formation of a second H2O molecule, indicating that phosphorus-doped monovacancy at the hollow site of bilayer graphene (PC3-BLG) is a promising non-PGM alternative to Pt/C catalysts under acidic conditions. These points suggest potential strategies for including carbon-allotrope-based materials in the design of efficient non-PGM catalysts for the ORR.