Sodium-ion batteries (SIBs) offer a viable alternative to partially or fully replace lithium ion batteries (LIBs) due to their lower cost and increased safety. This paper outlines the compositional optimizations, crystallographic evaluations, and electrochemical behavior of a novel mixed NASICON polyanionic compound, NaFe2PO4(SO4)2 (NFPS). X-ray photoelectron spectrometry (XPS) results showed that cobalt doping produces a higher concentration of oxygen defects compared to undoped samples. Scanning electron microscopy (SEM) analysis results revealed that the modified sample has more uniform pores and pore distribution. Brunauer-Emmett-Teller (BET) measurements showed that doping of Co2+ reduces the specific surface area of NFPS-Co0.08 compared to NFPS. This shortens the sodium ion diffusion pathway and promotes ion dynamics. The addition of Co2+ to the sample significantly improved its performance during galvanostatic charge-discharge tests. The electrochemical activity also is significantly enhanced by Co2+ doping. Na0.84Co0.08Fe2PO4(SO4)2 exhibits superior rate and cycling performance compared to pristine NFPS. After 80 cycles at 25 mA g-1, NFPS-Co0.08 retained discharge specific capacity of 60.8 mA h g-1, which is 1.24 times greater than that of NFPS.

Among the products of the electrocatalytic reduction of carbon dioxide (CO2RR), CO is currently the most valuable product for industrial applications. However, poor stability is a significant obstacle to CO2RR. Therefore, we synthesized a series of bimetallic organic framework materials containing different ratios of tungsten to copper using a hydrothermal method and used them as precursors. The precursors were then subjected to pyrolysis at 800 °C under argon gas, and the M-N bimetallic sites were formed after 2 h. Loose porous structures favorable for electrocatalytic reactions were finally obtained. The material could operate at lower reduction potentials than existing catalysts and obtained higher Faraday efficiencies than comparable catalysts. Of these, the current density of WCu-C/N (W:Cu = 3:1) could be stabilized at 7.9 mA ‧ cm-2 and the FE of CO reached 94 % at a hydrogen electrode potential of -0.6 V (V vs. RHE). The novel materials made with a two-step process helped to improve the stability and selectivity of the electrocatalytic reduction of CO2 to CO, which will help to promote the commercial application of this technology.