Layered-structure (NH4)2Mo4O13@N-doped porous carbon composite as a superior anode for lithium-ion batteries

Influence of ZIF-9 and ZIF-12 structure on the formation of a series of new Co/N-doped porous carbon composites as anode electrodes for high-performance lithium-ion batteries

A series of new Co/N-doped porous carbon composites, denoted as Co/CZIF-9 and Co/CZIF-12, containing Co nanoparticles encapsulated in nitrogen-doped carbon matrices were prepared by annealing Co-based zeolite imidazolate framework materials, ZIF-9 and ZIF-12, as the efficient precursors at different temperatures. The structural features of the as-synthesized composites at 900 °C were determined by analytical methods with high reliability. Consequently, Co/CZIF-12_900 exhibits a high first specific discharge capacity of 971.0 mA h g^-1 at a current density of 0.1 A g^-1. Notably, the specific discharge/charge capacity of Co/CZIF-12_900 reaches about 508.8 mA h g^-1 at 0.1 A g^-1 after 100 cycles. The outstanding behaviors can be accounted for by the efficient incorporation of hetero-nitrogen doping and the Co nanoparticles within the layered structure of porous carbon, enhancing electrical conductivity and structural stability and limiting volume change during the intercalation/deintercalation of Li⁺ ions. These findings suggest that the Co/CZIF-12_900 material could be employed as a promising anode electrode for energy storage products.

An Isopolymolybdate-Incorporated Metal-Organic Framework with Sulfite Oxidase-Mimicking Activity for Photocatalytic Oxidation of Sulfides Utilizing In Situ-Generated Singlet Oxygen

Developing new photocatalysts for sulfide oxidation utilizing in situ-generated 1O2 is very significant. Inspired by natural enzymatic processes, we synthesized a mimic sulfite oxidase (SO), {[Co(Mo4O13)(TPT)2]} (CoMo-TPT), by incorporating an isopolymolybdate anion [Mo4O13]2- into a 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT)-based metal-organic framework under mild hydrothermal conditions. In this structure, {Mo4O13} units with intrinsic SO-like catalytic sites are beneficial for the selective oxidation of sulfite and thioether. The ultraviolet-visible spectra of CoMo-TPT exhibited strong absorption from 250 to 650 nm and potential application in the utilization of solar energy. Mott-Schottky measurements indicated that CoMo-TPT is an n-type semiconductor with a LUMO value of -0.70 V (vs NHE) and a HOMO value of 1.39 V. The transient photocurrent responses with strong current density cycles with visible light indicated CoMo-TPT has a high photochemical activity. The lower resistance indicated that CoMo-TPT has a higher efficiency of photoinduced electron and hole separation. CoMo-TPT displayed a high efficiency of 99% and a selectivity of 97.3% in photocatalytic oxidation of sulfides by utilizing in situ-generated 1O2 through a tandem process of formation of H2O2 from O2 followed by catalyzed disproportionation of H2O2.

Facile Synthesis of MoP-RuP2 with Abundant Interfaces to Boost Hydrogen Evolution Reactions in Alkaline Media

Exploiting efficient electrocatalysts for hydrogen evolution reactions (HERs) is important for boosting the large-scale applications of hydrogen energy. Herein, MoP-RuP₂ encapsulated in N,P-codoped carbon (MoP-RuP₂@NPC) with abundant interfaces were prepared via a facile avenue with the low-toxic melamine phosphate as the phosphorous resource. Moreover, the obtained electrocatalyst possessed a porous nanostructure, had abundant exposed active sites and improved the mass transport during the electrocatalytic process. Due to the above merits, the prepared MoP-RuP₂@NPC delivered a greater electrocatalytic performance for HERs (50 mV@10 mA cm⁻²) relative to RuP₂@NPC (120 mV) and MoP@NPC (195 mV) in 1 M KOH. Moreover, an ultralow potential of 1.6 V was required to deliver a current density of 10 mA cm⁻² in the two-electrode configuration for overall water splitting. For practical applications, intermittent solar energy, wind energy and thermal energy were utilized to drive the electrolyzer to generate hydrogen gas. This work provides a novel and facile strategy for designing highly efficient and stable nanomaterials toward hydrogen production.