Phosphorus-doped nickel-gallium alloy and Ti4O7 nanofibers: A novel self-supporting bifunctional catalyst for oxygen electrocatalysis and Zn-air batteries

Abstract

Precious metal catalysts are widely recognized for their excellent efficiency in OER and ORR, but high cost and stability limit further commercial expansion. Carbon-based catalysts with large specific surface area, although a potential alternative to noble metal catalysts in terms of price and performance, are notoriously weak in terms of corrosion resistance in extreme environments. Metal catalysts are able to solve the above problems and are gradually coming into the limelight, but the control of morphology is not as good as that of carbon-based catalysts. Therefore, in order to solve the above problems together, the development of bifunctional catalysts with high efficiency, stability, low cost and excellent morphology has become a bright research direction. In this study, a new catalyst consisting of phosphorus-doped self-supported nanostructured Ti4O7 and nickel-gallium alloy particles was investigated using an electrostatic spinning process. Most of the previous studies have simply prepared Ti4O7 nanofibers without in-depth investigation on how to better control their morphology. In contrast, this study presents a universal set of experimental parameters for the development of very fine Ti4O7 nanospinning. With the help of this set of parameters, we develop a novel Ti4O7/C composite substrate nanofiber catalyst with an average diameter less than 297 nm. Its excellent morphology and corrosion resistance make it an inexpensive bifunctional catalyst with great potential. Relevant OER performed in 1 M KOH electrolyte shows that the catalyst has a low Tafel slope (80.77 mV dec−1), a small overpotential (282 mV at 10 mA cm−2), and excellent stability (up to 5000 cycles). In a strongly alkaline environment, the catalyst outperforms commercially available RuO2 (299 mV and 105.79 mV dec−1). In addition, the catalyst demonstrates a half-wave potential of 0.86 V in 0.1 M KOH electrolyte, exhibiting excellent ORR performance. The maximum power density (161 mW cm−2) and energy density (813 mA h gZn−1) of the zinc-air battery assembled with this catalyst exceeds the performance of the air battery using the Pt/C catalyst with better stability. In summary, this study achieves significant methodological advances and develops a novel bifunctional catalyst, which is of interest to a wide range of researchers.