CO2/H2 Separation by Synergistic Enhanced Hydrate Method with SDS and R134a.

The synergistic effect of thermodynamic promoter tetrafluoroethane (R134a) and kinetic promoter sodium dodecyl sulfate (SDS) can significantly improve the phase equilibrium conditions required for CO2 hydrate formation and promote rapid generation of CO2 hydrate. Based on this, this study investigates the influence of SDS and R134a synergy on the separation of CO2/H2 mixed gas using the hydrate method. The research reveals that without SDS addition, R134a hydrate forms first at the gas-liquid interface before CO2 hydrate induction, hindering gas-liquid exchange. The addition of SDS can inhibit the formation of the hydrate film, enhance the initiator effect of R134a in the CO2 hydrate formation process, accelerate the nucleation of CO2 hydrate, and thus synergistically strengthen the separation of CO2/H2 mixed gases. Hydrate formation can be achieved at a concentration of 100 ppm of SDS solution, and the synergistic growth effect of R134a and CO2 hydrate becomes more significant with increasing SDS concentration. Optimal separation efficiency and maximum H2 concentration are achieved at 500 ppm of SDS, with 42.29 and 54.88% separation efficiency and H2 concentration, respectively. Decreasing the initial charge temperature has little impact on separation efficiency but significantly reduces the induction time, reducing it to 3 min at 12 °C. This study improved the separation efficiency of CO2 and H2 mixed gas, providing a better reference for hydrogen purification by the hydrate method.

Self-Assembly of Metal-Organic Frameworks on Graphene Oxide Nanosheets and In Situ Conversion into a Nickel Hydroxide/Graphene Oxide Battery-Type Electrode.

Graphene oxide (GO) has been widely reported as a supercapacitor electrode. Especially, GO is usually utilized to composite with electrochemical active materials, such as transition-metal oxide/hydroxide/sulfide, due to its considerable conductivity and mechanical strength. However, the ideal design and treatment for compositing GO with active materials are still challenging. Herein, an Ni-metal-organic framework (MOF) was self-assembled on GO nanosheets via the solvothermal method and was subsequently etched into the Ni(OH)2-GO composite electrode material through a gentle hydrolysis strategy. The GO support enables fast electron transport within the composite material, and the nickel hydroxide growth on GO nanosheets can prevent their aggregation, guaranteeing rapid ion migration. The improved Ni(OH)2-GO battery-type electrode features outstanding stability (capacity retention of 108% at 8000 cycles) and a considerable specific capacity (SC) of 1007.5 C g-1 at a current density of 0.5 A g-1. Compared with MOF-derived Ni(OH)2 obtained through hydrolysis, Ni(OH)2-GO only contains 7.41% wt GO, while its SC is almost 50% higher. An asymmetric supercapacitor has an energy density of 65.22 W h kg-1 and a power density of 395.27 W kg-1 utilizing p-phenylenediamine-functional reduced GO as the negative electrode, and it can maintain 73.08% capacity during 8000 cycles at a current density of 5 A g-1.