Metal Organic Framework-Templated Synthesis of Bimetallic Selenides with Rich Phase Boundaries for Sodium-Ion Storage and Oxygen Evolution Reaction

Two-phase or multiphase compounds have been evidenced to exhibit good electrochemical performance for energy applications; however, the mechanism insights into these materials, especially the performance improvement by engineering the high-active phase boundaries in bimetallic compounds, remain to be seen. Here, we report a bimetallic selenide heterostructure (CoSe 2 /ZnSe) and the fundamental mechanism behind their superior electrochemical performance. The charge redistribution at the phase boundaries of CoSe 2 /ZnSe was experimentally and theoretically proven. Benefiting from the abundant phase boundaries, CoSe 2 /ZnSe exerts low Na + adsorption energy and fast diffusion kinetics for sodium-ion batteries and high activity for oxygen evolution reaction. As expected, excellent sodium storage capability, specifically a superb cyclic stability of up to 800 cycles for the Na 3 V 2 (PO 4 ) 3 ∥CoZn-Se full cell, and efficient water oxidation with a small overpotential of 320 mV to reach 10 mA cm –2 were obtained. This work demonstrates the importance of phase boundaries in bimetallic compounds to boost the performance in various fields.