Nanocrystalline CoSe2/(Cu,Co)Se2: an archetypal bimetallic selenide anode material for high-efficiency electrocatalytic oxygen evolution reaction†

Abstract

The advancement of high-efficiency electrocatalysts for oxygen electrochemistry in energy conversion and storage systems is crucial for contemporary technological development. Herein, a novel synthetic strategy (kinetic crystal growth along with in situ material capping, followed by aqueous-phase anion exchange) has been devised to prepare nanocrystalline CoSe₂/(Cu,Co)Se₂, a new two-phase selenide material with a surface conducive to wetting, high specific BET surface area, monomodal pore size distribution and inter-crystallite mesoporosity. The material was explored as a potential electrocatalyst for the oxygen evolution reaction (OER) in an alkaline medium, and the resultant electrochemical analyses demonstrated low-overpotential electrocatalytic OER, very low Tafel slope, and high turnover frequency for the OER process. The amperometric i vs. t and chronopotentiometry studies during electrocatalytic OER revealed excellent current retention, persistent potential requirement, and continuously low charge transfer resistance during the continuous OER for long duration. The nanocrystalline CoSe₂/(Cu,Co)Se₂ offers interphase chemical synergetics for enhanced conductivity and electronic affinity for O⁻ adsorption, improved charge transferability, more electroactive surface area, and enhanced accessibility to catalytic sites and facilitates effective diffusion of electroactive ions, which improve the overall kinetics for the electrocatalytic OER. In addition, the hierarchical inter-crystallite porosity of CoSe₂/(Cu,Co)Se₂ ensures microstructural robustness during ion intercalation/de-intercalation and facilitates the release of gaseous oxygen generated during continuous OER for long duration. This study demonstrates the strategic chemical and microstructural engineering of non-noble multi-metal selenides of multiphase synergetics, which may pave the way for the future development of high-efficiency energy conversion and storage systems reliant on oxygen electrochemistry.