Activated Petroleum Vacuum Residue for Selective Oxygen Reduction Reaction with Kinetic Analysis

The development of heteroatom-doped and metal-free porous carbons (PCs) as alternatives to metal-based materials remains a significant challenge in modern electrocatalysis. Conversely, waste from petroleum, particularly petroleum vacuum residue, has much potential as a carbon-rich precursor for the development of porous carbons for electrocatalysis. The new catalysts were synthesized using petroleum vacuum residue obtained from the local petroleum industry. The porous carbons (PCs) were synthesized as catalysts using a simple single-step activation at 800 °C for 2 h in the presence of polyphosphoric acid. PCs exhibit a substantial surface area of approximately 3300 m2/g and displays a combination of micro- and meso-porosities, along with a significant degree of graphitization. Spectroscopic analysis indicated a phosphorus doping content of approximately 10%. PCs were evaluated for their performance in the oxygen reduction reaction (ORR), which is a significant challenge and benchmark in the field of electrochemistry. In order to evaluate the importance of the doped heteroatoms’ environment in ORR, the structural characteristics and the variations in the activating agents for the formation of PCs were compared. A rotating ring-disc electrode was used to determine the selectivity for H2O2, which reached 85%. The selectivity is explained by a kinetic analysis. The ORR efficiency of the electrocatalysts under alkaline conditions demonstrates the promise of petroleum vacuum residue-derived PCs for the sustainable use of petroleum waste.