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.