Synthesis of novel cubic Ni2Mo3N and its electronic structure regulation by vanadium doping towards high-efficient HER electrocatalyst

Ni,S co-doped Cu dendrites decorated with core-shell architecture assisted by MOF and Fe0.92Co0.08S nanoflakes on nanocellulose/graphene fibers for fabrication of flexible wire-type micro-supercapacitor

One-dimensional micro-supercapacitors (1D micro-SCs) have been regarded as an efficient energy storage system to fulfill the ever-growing need for miniaturized electronics. Designing multi-dimensional nanoarchitectures on fibrous microelectrodes is an effective strategy to build a high-performance 1D micro-SC. In this work, Ni,S-doped Cu was firstly prepared on Cu wire as a micro-sized 1D current collector through Cu electrodeposition using a H2 bubble template and then co-doped with nickel and sulfur. Benefiting from the high electrical/thermal conductivity of Cu, and the highly electroactive sites of Ni and S as well as the 3D porous architecture, the deposited Ni,S-doped Cu provided a platform for growing active substances. Thereafter, cobalt carbonate hydroxide (CoCH) pine-like nanoneedle integrated ZIF-67 polyhedrons were synthesized on a foam-like skeleton and converted into NiMoCo-layered triple hydroxide (LTH)/Ni,S-doped Cu shish-kebab type nanoarrays by applying a hydrothermal method. Finally, Ni2Mo3N-CoN/Ni,S-doped Cu was prepared via nitridation. The potent interactions and synergy between components realized a well-organized hybrid nanoarchitecture consisting of dodecahedrons decorated on needle-like arrays within a 3D framework with rich redox properties, rapid ion/electron transfer dynamics and high electroactivity. In comparison to the LTH obtained from the electrodeposition method (without the ZIF-67 precursor) and that derived from leaf-like ZIF-Co, this modified microfiber exhibited a high charge storage capacity of 1.5 mA h cm-2 (149.9 mA h cm-3 and 0.187 mA h cm-1) at 4 mA cm-2 and possesses an excellent durability of 98.4% after 5000 cycles. Additionally, FeCoS nanoflakes were electrodeposited using carbon fiber coated with an rGO-nanocellulose hydrogel (GNCH) and employed as a negative 1D microelectrode, which delivered a high specific capacitance of 1223 mF cm-2 (83 F cm-3, 232.4 mF cm-1) at 4 mA cm-2 with a superior cyclic lifespan. Ultimately, the assembled 1D flexible micro-device (Ni2Mo3N-CoN/Ni,S-doped Cu@CW//FeCoS/GNCH@CF) yielded an energy density of 7.2 mW h cm-3 at a power density of 294 mW cm-3 and outstanding cycling stability in PVA/KOH electrolyte and preserved the capacitive performance under various bending states. This research highlights that assembled 1D micro-SCs have a high potency for next-generation portable/wearable energy-supply microelectronics.

Direct One-Step Growth of Bimetallic Ni2Mo3N on Ni Foam as an Efficient Oxygen Evolution Electrocatalyst

A simple and economical synthetic route for direct one-step growth of bimetallic Ni2Mo3N nanoparticles on Ni foam substrate (Ni2Mo3N/NF) and its catalytic performance during an oxygen evolution reaction (OER) are reported. The Ni2Mo3N/NF catalyst was obtained by annealing a mixture of a Mo precursor, Ni foam, and urea at 600 °C under N2 flow using one-pot synthesis. Moreover, the Ni2Mo3N/NF exhibited high OER activity with low overpotential values (336.38 mV at 50 mA cm-2 and 392.49 mV at 100 mA cm-2) and good stability for 5 h in Fe-purified alkaline electrolyte. The Ni2Mo3N nanoparticle surfaces converted into amorphous surface oxide species during the OER, which might be attributed to the OER activity.