Promotion of borophene/NiO-based electrocatalyst for oxygen evolution reaction

Abstract

Electrochemical water splitting has great potential for converting electricity into clean energy through electrode reactions. However, the anodic oxygen evolution reaction (OER) exhibits serious drawbacks such as: (i) high overpotential, slow reaction dynamics, limited robustness at high current density, and (ii) high cost of standard catalysts in OER (IrO2 or RuO2). Therefore, in our study, we address those issues and present a new composite based on 2D borophene functionalized with nickel oxide nanoparticles with highly active electrocatalytic properties in OER, with a low overpotential of 191 mV reaching j = 10 mA/cm2 and Tafel slope of 44 mV/dec. Additionally, the structure showed electrochemical and physical stability during long-term measurements, with excellent potential retention of 99.9 % at 50 mA/cm2. The electrochemical surface area (ECSA) revealed an increase in the number of active sites available for the reaction to occur, with respect to individual components of composites. Detailed spectroscopic and microscopic analyses of the electrocatalyst conducted before and after OER allowed us to propose insight into the reaction mechanism indicating the synergy between borophene and NiO nanoparticles (facilitated electron charge transfer and additional reaction intermediate such as NiB12O14(OH)10). The proposed fabrication process of borophene functionalized by NiO is facile, low-cost, and scalable. Moreover, this strategy offers an additional avenue to explore a 2D family of electrocatalysts in OER enriching the current state of the art in the field.