An effective poly(p-phenylenevinylene) polymer adhesion route toward three-dimensional nitrogen-doped carbon nanotube/reduced graphene oxide composite for direct electrocatalytic oxygen reduction

Heteroatom-doped nanocarbons have excellent potential for use in the oxygen reduction reaction (ORR). However, construction of three-dimensional (3D) N-doped carbon materials with good electrocatalytic performance remains a challenge. Herein, a poly(p-phenylenevinylene) (PPV)-precursor adhesion route was developed for construction of 3D N-doped reduced graphene oxide-PPV calcined-carbon nanotubes (N-RGO-PPV(c)-CNTs). In the synthesis, the PPV-precursor plays the role of a "glue" for strong adhesion of the RGO and CNTs. At high temperature, PPV can undergo transformation from the glassy state to a viscous state. Thus, the N-RGO-PPV(c)-CNT composite with multi-porous structure and ridge-like folded graphene flakes could be formed during nitridation at high temperature, which was favorable for production of more active sites for the ORR. As an ORR catalyst, the N-RGO-PPV(c)-CNT composites exhibited superior catalytic activity in alkaline electrolyte. The obtained onset potential (E_onset) of 0.92 V and catalytic current density of 5.7 mA·cm^–2 at 0.6 V (vs. RHE) are comparable to those of the 20% Pt/C composite (0.98 V and 5.2 mA·cm^–2). The electron transfer number for the N-RGO-PPV(c)-CNT catalyst was about 3.99, which is close to that of the 20% Pt/C (4.01) catalyst. Notably, the optimal N-RGO-PPV(c)-CNT catalyst shows better durability and methanol tolerance than commercial 20% Pt/C. The good performance of the N-RGO-PPV(c)-CNT catalyst for the ORR may be attributed to the synergistic effects of the unique 3D structure for effective mass-transfer, the effective N-doping for production of more active sites, and the good contact between the RGO and CNTs for easy charge-transfer.