Metal\nOrganic Framework-Templated Synthesis of Bimetallic\nSelenides with Rich Phase Boundaries for Sodium-Ion Storage and Oxygen\nEvolution Reaction

Abstract

Two-phase\nor multiphase compounds have been evidenced to exhibit\ngood electrochemical performance for energy applications; however,\nthe mechanism insights into these materials, especially the performance\nimprovement by engineering the high-active phase boundaries in bimetallic\ncompounds, remain to be seen. Here, we report a bimetallic selenide\nheterostructure (CoSe₂/ZnSe) and the fundamental mechanism\nbehind their superior electrochemical performance. The charge redistribution\nat the phase boundaries of CoSe₂/ZnSe was experimentally\nand theoretically proven. Benefiting from the abundant phase boundaries,\nCoSe₂/ZnSe exerts low Na⁺ adsorption energy\nand fast diffusion kinetics for sodium-ion batteries and high activity\nfor oxygen evolution reaction. As expected, excellent sodium storage\ncapability, specifically a superb cyclic stability of up to 800 cycles\nfor the Na₃V₂(PO₄)₃∥CoZn-Se\nfull cell, and efficient water oxidation with a small overpotential\nof 320 mV to reach 10 mA cm^–2 were obtained. This\nwork demonstrates the importance of phase boundaries in bimetallic\ncompounds to boost the performance in various fields.