Interface Enables Faster Surface Reconstruction in a Heterostructured CuSe y /NiSe x Electrocatalyst for Realizing Urea Oxidation.

Creating affordable electrocatalysts and understanding the real-time catalytic process of the urea oxidation reaction (UOR) are crucial for advancing urea-based technologies. Herein, a Cu-Ni based selenide electrocatalyst (CuSe y /NiSe x /NF) was created using a hydrothermal technique and selenization treatment, featuring a heterogeneous interface rich in Cu2- x Se, Cu3 Se2 , Ni3 Se4 , and NiSe2 . This catalyst demonstrated outstanding urea electrooxidation performance, achieving 10 mA cm-2 with just 1.31 V and sustaining stability for 96 h. Through in-situ Raman spectroscopy and ex-situ characterizations, it is discovered that NiOOH is formed through surface reconstruction in the UOR process, with high-valence Ni serving as the key site for effective urea oxidation. Moreover, the electrochemical analysis revealed that CuSe y had dual effects. An analysis of XPS and electrochemical tests revealed that electron transfer from CuSe y to NiSe x within the CuSe y /NiSe x /NF heterostructure enhanced the UOR kinetics of the catalyst. Additionally, according to the in-situ Raman spectroscopy findings, the existence of CuSe y facilitates a easier and faster surface reconstruction of NiSe x , leading to the creation of additional active sites for urea oxidation. More significantly, this work provides an excellent "precatalyst" for highly efficient UOR, along with an in-depth understanding of the mechanism behind the structural changes in electrocatalysts and the discovery of their true active sites.