Porous Carbon from Vacuum Residue as an Effective Electrocatalyst for a 2e⁻ Oxygen Reduction Reaction in Alkaline Media

The development of an efficient and selective catalyst for hydrogen peroxide (H₂O₂) electrosynthesis remains challenging, primarily, due to the competitive side reaction of 4 e⁻ oxygen reduction to H₂O. In this work, we report activated carbons prepared from vacuum residue (VR) as a carbon precursor. VR is activated with phosphoric acid to obtain activated VR (VR-PA) as an electrocatalyst for an effective 2 e⁻ oxygen reduction reaction (ORR) to form H₂O₂. The VR-PA has been characterized for surface functional groups and porous structure to obtain insights of the surface properties that are relevant in the electrode−electrolyte interface for potential applications in electrocatalysis. The electrocatalytic activity toward the ORR of the VR-PA has been explored by rotating disc and ring disc electrode measurements under hydrodynamic conditions to reveal the selectivity of 2 e⁻ ORR with ∼88% yield of H₂O₂. Activation of VR with phosphoric acid at 800 °C retained the original nitrogen and sulfur content of the VR which resulted in triply N-, S-, and P-doped activated VR. This work features the effect of the elemental composition of VR and the activation using phosphoric acid in the interfacial electrode−electrolyte processes in the ORR for selective H₂O₂ production.