WO2–N co-doped 2D Carbon nanosheets as multifunctional additives for enhancing the electrochemical hydrogen storage performance of Co2B

Abstract

Co₂B, with its high theoretical hydrogen storage capacity, is a potential solid-state hydrogen storage material. However, its poor cycling life limits its practical application. In this work, in order to improve the cycling stability and reversibility of hydrogen absorption and desorption of Co₂B, we propose to use WO₂–N–C nanosheets as dopants to mix with Co₂B, thereby enhancing its practical performance. Two-dimensional tungsten oxide-nitrogen-carbon (WO₂–N–C) nanosheets was syntheized via a liquid-phase approach, using a tungstenate-polydopamine precursor followed by thermal treatment. Subsequently, these WO₂–N–C nanosheets were compounded with cobalt boride (Co₂B) particles through ball milling at various ratios of 1%, 3%, and 5%, which were confirmed by XRD (X-ray diffraction) and SEM (Scanning Electron Microscope) methods. Employing a comprehensive suite of electrochemical analyses, including corrosion potential measurements, polarization curves, step voltammetry, and electrochemical impedance spectroscopy (EIS), we found that the incorporation of WO₂–N–C significantly enhances the corrosion resistance and electrochemical activity of Co₂B. Furthermore, cyclic life tests revealed that the WO₂–N–C-doped Co₂B composites exhibit superior discharge capacities and capacity retention rates compared to pristine Co₂B. Notably, the 3% WO₂–N–C-doped Co₂B composite demonstrated the optimal electrochemical performance, achieving a maximum discharge specific capacity of 555 mAh g⁻¹ and maintaining 82% of its initial capacity after 50 cycles. Our findings underscore the dual role of WO₂–N–C in not only augmenting the surface electrochemical activity of Co₂B but also providing a protective surface layer, thereby enhancing its overall electrochemical performance.