One-step chemical reduction of graphene oxide with oligothiophene for improved electrocatalytic oxygen reduction reactions

Oligothiophene (nTP, n = 1, 2, 3) has been used as the reductant for the first time in the preparation of graphene by the reduction of graphene oxide (GO). A simple single-step chemical approach has been developed to reduce and/or functionalize GO with nTP. The reaction takes place at room temperature under stirring of a suspension of GO and nTP in MeCN. The nTP has been grafted onto the surface of GO by reacting epoxy groups together with the reduced graphene oxide (rGO). It was observed that increasing the thiophene ring (hereafter, thiophene is referred to as TP; 2,2′ bithiophene as 2TP; and 2,2′:5′,2″ terthiophene as 3TP) can enhance the reduction reaction. All instrumental experiments have confirmed that nTP not only covalently bonded to the GO but also partly restored the conjugate structure of GO, as a reducing agent. The resultant rGO with 3TP (rGO3TP) has been demonstrated to show remarkable electrocatalytic activity toward oxygen reduction reaction (ORR) compared to typical rGO. The observed ORR electrocatalytic activity induced by the intermolecular charge-transfer provides a general approach to various carbon-based metal-free ORR catalysts.