Water splitting by MnFe2O4/Na2CO3 reversible redox reactions

Sodium Manganese Ferrite Water Splitting Cycle: Unravelling the Effect of Solid-Liquid Interfaces in Molten Alkali Carbonates

In this work, the Na2CO3 of the sodium manganese ferrite thermochemical cycle was substituted by different eutectic or eutectoid alkali carbonate mixtures. Substituting Na2CO3 with the eutectoid (Li0.07Na0.93)2CO3 mixture resulted in faster hydrogen production after the first cycle, shifting the hydrogen production maximum toward shorter reaction times. Thermodynamic calculations and in situ optical microscopy attributed this fact to the partial melting of the eutectoid carbonate, which helps the diffusion of the ions. Unfortunately, all the mixtures exhibit a significant loss of reversibility in terms of hydrogen production upon cycling. Among them, the nonsubstituted Na mixture exhibits the highest reversibility in terms of hydrogen production followed by the 7%Li-Na mixture, while the 50%Li-Na and Li-K-Na mixtures do not produce any hydrogen after the first cycle. The loss of reversibility is attributed to both the formation of undesired phases and sintering, the latter being more pronounced in the eutectic and eutectoid alkali carbonate mixtures, where the melting of the carbonate is predicted by thermodynamics.

Hydrogen Recovery from Waste Aluminum-Plastic Composites Treated with Alkaline Solution

An alternative solution to the problem of aluminum-plastic multilayer waste utilization was suggested. The process can be used for hydrogen generation and layer separation. Three different sorts of aluminum-plastic sandwich materials were treated with an alkali solution. In the temperature range of 50-70 °C, for tablet blisters of polyvinylchloride and aluminum (14.8 wt.%), the latter thoroughly reacted in 15-30 min. For sheets of paper, polyethylene, and aluminum (20 wt.%), full hydrogen 'recovery' from reacted aluminum component took 3-8 min. From the lids of polyethylene terephthalate, aluminum (60 wt.%), and painted polyethylene with perforations, the aluminum was consumed after 45-105 min. The effect of perforations was the reduction of the process duration from nearly 90 min for the lids with no perforations to nearly 45 min for the perforated ones (at 70 °C). Perforations provided better contact between the aluminum foil, isolated between the plastic layers, and the alkali solution. Hydrogen bubbles originating near those perforations provided foil separation from the upper painted plastic layer by creating gas gaps between them. The remaining components of the composite multilayer materials were separated and ready for further recycling.