Ultrafine MoP Nanoparticle Splotched Nitrogen-Doped Carbon Nanosheets Enabling High-Performance 3D-Printed Potassium-Ion Hybrid Capacitors

Size engineering is deemed to be an adoptable method to boost the electrochemical properties of potassium-ion storage; however, it remains a critical challenge to significantly reduce the nanoparticle size without compromising the uniformity. In this work, a series of MoP nanoparticle splotched nitrogen-doped carbon nanosheets (MoP@NC) is synthesized. Due to the coordinate and hydrogen bonds in the water-soluble polyacrylamide hydrogel, MoP is uniformly confined in a 3D porous NC to form ultrafine nanoparticles which facilitate the extreme exposure of abundant three-phase boundaries (MoP, NC, and electrolyte) for ionic binding and storage. Consequently, MoP@NC-1 delivers an excellent capacity performance (256.1 mAh g(-1) at 0.1 A g(-1)) and long-term cycling durability (89.9% capacitance retention after 800 cycles). It is further confirmed via density functional theory calculations that the smaller the MoP nanoparticle, the larger the three-phase boundary achieved for favoring competitive binding energy toward potassium ions. Finally, MoP@NC-1 is applied as highly electroactive additive for 3D printing ink to fabricate 3D-printed potassium-ion hybrid capacitors, which delivers high gravimetric energy/power density of 69.7 Wh kg(-1)/2041.6 W kg(-1), as well as favorable areal energy/power density of 0.34 mWh cm(-2)/9.97 mW cm(-2).

Automated summary

In this study, a series of MoP nanoparticle splotched nitrogen-doped carbon nanosheets (MoP@NC) were successfully synthesized, where MoP was uniformly confined in a 3D porous NC to form ultrafine nanoparticles facilitating ionic binding and storage. MoP@NC-1 demonstrated excellent performance and cycling stability, and was used as a highly electroactive additive in 3D printing ink to fabricate high-performance 3D-printed potassium-ion hybrid capacitors.