High-configurational Entropy Materials for Zn-Based Battery System

The advantages of aqueous zinc batteries are high energy density, stability, and low cost. The zinc-nitrate system converts nitrate waste into high-value ammonia and electricity. Highly active and stable catalysts are important to enhance the nitrate reduction reaction (NO_³RR) and the performance of aqueous zinc-nitrate batteries. Here, we demonstrate the enhancement of NO3RR by exploiting the synergy among multi-metals within Zeolitic Imidazolate Frameworks (ZIFs) enabled by high configurational entropy.
 High-configurational-entropy materials exhibit high catalytic activity and stability due to configurational entropy (>1.6R), while ZIFs, porous zeolite-like MOFs (Metal-Organic Frameworks), have large surface areas for catalysis and adsorption. The metals were selected based on the following considerations: Co, Zn, and Mn were chosen for their compatibility with the ZIF topology; Ni for its active sites; and Cu for its effectiveness in stabilizing intermediates. We prepared CoZnMn-ZIF at room temperature, followed by Cu and Ni ion exchange and subsequent carbonization. Using Powder X-Ray Diffraction (PXRD), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS), we demonstrated that the resulting multi-metal ZIF was single-phase, exhibited a homogeneous distribution of metals, and had a configurational entropy of 1.2–1.3R. Electrochemical characteristics such as overpotential and Charge Transfer Resistance (R_^ct) were measured by LSV, EIS, and CA. The lowest overpotential and the highest current density were observed for carbonized Cu- and Ni-exchanged CoZnMn-ZIF among the examined catalysts. These findings suggest that a multi-metal ZIF with high configurational entropy is a promising catalyst for NO3RR in an aqueous zinc–nitrate battery.