Oxygen-vacancy and phosphorus-doping enriched NiMoO4 nanoarrays for high-energy supercapacitors

Abstract

Exploring electrode materials with high effective surface and abundant active sites takes on a critical significance in achieving high-energy supercapacitors. Herein, the oxygen vacancies (Ov) and P-doping enriched NiMoO4 nanosheet arrays were synthesized through the combination of phosphorization and N2 plasma treatment. The combination strategy makes it possible to sharply increase and modulate the Ov content. The optimized P-NiMoO4-N2 is found with the highest Ov content, and the capacitive activity is well consistent with the increase in the Ov content among all samples. As revealed by experimental results, rich Ov increases the electrochemically accessible active-sites while enhancing the intrinsic conductivity. Thus, the optimized P-NiMoO4-N2 is enabled to reach a high capacity of 2180 F g−1 at a current density of 1 A g−1 and remains 83.9 % at 10 A g−1 with high cycling stability. After being assembled with activated carbon as the negative electrode, the asymmetric supercapacitor exhibits a high energy density of 56.8 Wh kg−1 at 0.75 kW kg−1 and maintains 41.6 Wh kg−1 at 15 kW kg−1. This work may create a novel path to enrich and adjust Ov in metal oxides for high-capacity and high-power supercapacitors.