Graphene featuring imidazolium rings and electrostatically immobilized polyacrylate chains as metal-free electrocatalyst for selective oxygen reduction to hydrogen peroxide

While graphene-based materials hold a strong potential as electrocatalysts, owing to their astonishing properties and functionalization capability, their intrinsic catalytic activity is more often masked under the umbrella of the precious and industrial metals that are used as counterparts for boosting the electrocatalytic performance. In the present work, we envisioned and realized a simple, stepwise surface engineering path for the modification of graphene oxide, aiming at elevating its intrinsic electrocatalytic activity, excluding any metals, towards the oxygen reduction reaction (ORR). More specifically, oxidized graphene was initially covalently decorated with amphoteric imidazole rings, which were then converted to the corresponding imidazolium counterparts. At the last step, anion exchange of the grafted imidazolium species was performed to immobilize via electrostatic interactions polyacrylate chains. The electrocatalytic performance of the so-formed graphene-based ensembles towards the ORR in alkaline media was evaluated, unveiling the 2e- reduction of oxygen, selectively producing hydrogen peroxide. The results indicate that both covalent and non-covalent surface engineering of graphene with organic chains matters towards electrocatalysis and should not be considered negligible. Our findings and insights provided are a stepping stone on the quest of graphene-based ensembles as metal-free electrocatalysts.

Automated summary

This study presents a surface engineering approach to modify graphene oxide and enhance its intrinsic electrocatalytic activity towards the oxygen reduction reaction (ORR) without using any metals. The results showed that both covalent and non-covalent surface engineering of graphene with organic chains play an important role in electrocatalysis and should not be ignored.