Novel System Sequesters CO2 And Generates Electricity

A recent study, affiliated with UNIST (South Korea) has unveiled a novel system, capable of producing hydrogen and electricity quickly and effectively while cutting carbon dioxide (CO2) emissions significantly.  Published in the journal Nano Energy, this breakthrough has been carried out by Professor GunTae Kim and his research team in the School of Energy and Chemical Engineering at UNIST. In this study, the research team succeeded in developing a membrane-free aqueous metal-CO2 battery. Unlike the existing aqueous metal-CO2 systems, the new battery is not only easier to manufacture, but also allows continuous operation with one type of electrolyte.

The research team designed a membrane-free (MF) Mg-CO2battery, as an advanced approach to sequester CO2 emissions by generating electricity and value-added chemicals without any harmful by-products. According to the research team, their MF Mg-CO2 battery operates based on the indirect utilization of CO2with facile hydrogen generation process. It has been also found that the new battery exhibits high faradaic efficiency of 92.0%.

In order to translate the newly-developed laboratory-scale MF Mg-CO2 battery technology into a commercial reality, we have envisioned an operational prototype system that produces electricity and value-added chemicals, as a cornerstone to better support sustainable human life from CO2 and earth-abundant renewable power (e.g., wind, solar, seawater),” noted the research team.

The MF Mg-CO2 battery system has a structure similar to that of hydrogen fuel cells for use in cars, since it only requires a Mg-metal negative electrode, an aqueous electrolyte, and a positive-electrode catalyst. However, unlike the existing fuel cells, they are based on aqueous electrolytes. As a result, the newly-developed MF Mg-CO2 battery had successfully sequestered CO2 emissions by generating electricity and value-added chemicals without any harmful by-products.

Our findings indicate great benefits for the newly-developed MF Mg-CO2 battery technology to produce various value-added chemicals of practical significance and electricity from CO2without any wasted by-products,” noted the research team. “Through this we have opened the door to electrochemical utilization of CO2 with indirect circulation for future alternative technologies.”


Lead-Free Perovskites Boost Generation Of Electric Current

Lead-based perovskites are quite promising in applications of large-scale photovoltaic technology. However, toxicity is one of the crucial issues in these materials.

In the search for Lead-free perovskite, UNIST scientists have taken a major step forward toward a new generation of solar cells. They have developed new perovskite material that works as a charge regenerator with dye‐sensitized solar cells and have higher efficiency and stability.

Scientists used the vacancy‐ordered double perovskite (Cs2SnI6). They primarily examined the charge transfer mechanism of Cs2SnI6 with the aim of clarifying the function of its surface state.

For this reason, a 3‐electrode system was produced to observe charge exchange through the surface state of Cs2SnI6.  “Due to a high volume of electrical charges in organic dyes that show high connectivity with the surface state of Cs2SnI6, more electric current was generated,” said Byung-Man Kim from the Department of Chemistry at UNIST. “Consequently, Cs2SnI6 shows efficient charge transfer with a thermodynamically favorable charge acceptor level, achieving a 79% enhancement in the photocurrent density compared with that of a conventional liquid electrolyte.”


Let Your Skin Play Music

A variety of nanomaterials have been used over the years in loudspeakers and microphones. Nanoparticles have replaced permanent magnets in loudspeakers and a thin film of carbon nanotubes has done pretty much the same. And, of course, someone tried to use graphene to reproduce sound for microphones.

Now researchers at Ulsan National Institute of Science and Technology (UNIST) in South Korea have made a nanomembrane out of silver nanowires to serve as flexible loudspeakers or microphones. The researchers even went so far as to demonstrate their nanomembrane by making it into a loudspeaker that could be attached to skin and used it to play the final movement of a violin concerto—namely, La Campanella by Niccolo Paganini.

In research described in the journal Science Advances, the Korean researchers embedded a silver nanowire network within a polymer-based nanomembrane. The decision to use silver nanowires rather than the other types of nanomaterials that have been used in the past was based on the comparative ease of hybridizing the nanowires into the polymer. In addition, the researchers opted for nanowires because the other materials like graphene and carbon nanotubes are not as mechanically strong at nanometer-scale thickness when in freestanding form, according to Hyunhyub Ko, an associate professor at UNIST and coauthor of the research. It is this thickness that is the critical element of the material.

The biggest breakthrough of our research is the development of ultrathin, transparent, and conductive hybrid nanomembranes with nanoscale thickness, less than 100 nanometers,” said Ko. “These outstanding optical, electrical, and mechanical properties of nanomembranes enable the demonstration of skin-attachable and imperceptible loudspeaker and microphone.”

The nanomembrane loudspeaker operates by emitting thermoacoustic sound through the oscillation of the surrounding air brought on by temperature differences. The periodic Joule heating that occurs when an electric current passes through a conductor and produces heat leads to these temperature oscillations.