Sandwich-like composite with two-dimensional van der waals heterojunction as high-performance electrocatalyst for zinc-air battery

With increasing concerns about the energy crisis and environmental pollution, growing emphasis has been placed on the development of sustainable energy technology such as zinc-air batteries (ZABs) [1-2]. The electrochemical oxygen reduction reaction (ORR) is the key electrochemical process for ZABs. However, the inherently slow reaction kinetics severely limit the energy conversion efficiency and electrocatalysts are necessary to accelerate the reaction kinetics and decrease the overpotential. Although noble metal catalysts (e.g., Pt/C) exhibit excellent catalytic performance, its high cost, susceptibility to poisoning, and poor long-term stability restrict the large-scale implementation. Consequently, the development of high-performance, cost-effective, and stable non-noble metal catalysts has become a key research priority. Titanium nitride (TiN), as one of the non-noble metal nitride, have gained significant attention in recent years due to their excellent corrosion resistance, high conductivity and catalytic potential, especially for ORR. However, the easy aggregation of TiN nanoparticles (NPs) results in insufficient exposure of active sites. To overcome this issue, one effective strategy is to construct TiN/NC composites by using 2D nitrogen-doped carbon (NC) as a substrate to anchor TiN NPs. Despite this, TiN/NC still faces limitations due to its inherent low catalytic activity. As reported [3], constructing hetero structured electro catalysts by assembling the building blocks depending on various physical/chemical interactions is a general approach to improve catalytic properties. In this work, a sandwich-like structured electrocatalyst (Co-MOF/TiN/NC) with two-dimensional van der Waals heterojunctions was synthesized using high-temperature solid-state and room-temperature ultrasound methods, in which the 2D Co-MOF nanosheets uniformly loaded onto the TiN/NC substrate. X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS) analyses reveal that the work function difference between Co-MOF and TiN/NC drives electron transfer, thereby regulating the oxidation states of Ti and Co and increasing the numbers of catalytic active sites. Ultimately, the Co-MOF/TiN/NC electrocatalyst outperforms the commercial Pt/C catalyst in ORR performance. Moreover, the zinc-air battery assembled with Co-MOF/TiN/NC demonstrate excellent performance. This work provides a new perspective for the design of heterojunction catalysts to apply in the energy field.

Dr. Yige Zhao is a materials scientist specializing in electrocatalytic materials and their preparation technologies. She holds a PhD in Materials Science and Engineering from Beijing University of Chemical Technology. Dr. Zhao has led several scientific research projects and has published extensively in the field of sustainable energy. Currently, she serves as an associate professor at Zhengzhou University in China.