Sulfur-doped carbon nanofibers as support for tantalum oxides bifunctional catalysts for the oxygen reduction and evolution reactions

Highly efficient, low-cost and stable bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly desirable for the development of green electrochemical energy storage and conversion devices. Here, we report the synthesis of sulfur-doped carbon nanofibers (CNF) as support for tantalum oxide nanoparticles. Carbon nanofibers and tantalum oxides represent a durable choice for oxygen electrocatalysis, but an improvement of catalytic activity is required. Upon doping, sulfur is found to be mainly bonded to carbon as C-S-C species (more than 80%). The results show that the effective incorporation of sulfur in the support has a clear positive effect on the electroactivity of the tantalum oxide catalysts. It causes a decrease of OER/ORR overpotential of 80 mV with respect to the undoped counterpart, with special improvement in the ORR. The new catalysts have shown an interesting bifunctional behavior for the OER and ORR, as well as a good stability through time.

Automated summary

In this study, highly efficient, low-cost, and stable bifunctional catalysts for oxygen reduction and oxygen evolution reactions were synthesized. By incorporating sulfur into carbon nanofiber support, the catalytic activity of tantalum oxide nanoparticles was significantly improved, resulting in a decrease of overpotential for oxygen reduction and evolution reactions by 80mV, and demonstrating good stability.