Recently, the team of Ren Wencai and Cheng Huiming of the Shenyang National Research Center for Materials Science, Institute of Metal Research, Chinese Academy of Sciences prepared a class of two-dimensional transition metal phosphorous sulfides (MPX3, where M = Cd, Mn, Fe, Co, Ni, Zn, Cr, etc., X = S or Se) nanosheets assembled film, found that the transition metal vacancies make this type of film have ultra-fast ion transport performance. On October 30, the international academic journal "SCIENCE" published related results under the title "CdPS3 nanosheet films with high proton conductivity induced by Cd vacancies".
Ion transport in nanopores is essential for energy storage and conversion applications. For example, proton and lithium ion conductive membranes are key materials for fuel cells and lithium ion batteries, respectively. The Nafion membrane produced by DuPont is currently the most commonly used commercial proton conducting membrane. It uses sulfonic acid groups as the proton donor center. Protons are conducted through a network of water molecules formed in nanopores. The proton conductivity can reach 0.2 S/ cm. However, under high temperature (>80 C) and/or low humidity conditions, its performance will be severely degraded due to the decrease in water content. In recent years, people have developed a variety of proton conducting membranes, including membrane materials based on MOF, biomaterials and graphene oxide. These membrane materials also use functional groups (such as phosphoric acid, carboxyl, hydroxyl, etc.) as the proton donor center, but their performance is still far behind Nafion membrane.
The researchers found that the Cd0.85PS3Li0.15H0.15 film is an ion conductor dominated by proton transport, with a conductivity of up to 0.95 S/cm at 90°C and 98% relative humidity, which is currently reported as a water-phase proton transport material The performance is the highest, and it still maintains a high proton conductivity under low temperature and low humidity conditions. Further research found that Cd vacancies not only provide a large number of proton donor centers, but also make the film have excellent hydration properties, and protons are easily desorbed from the vacancies in the presence of water molecules, so that the film exhibits excellent proton conduction characteristic. In addition, they also found that Cd0.85PS3Li0.3 and Mn0.77PS3Li0.46 films have ultra-fast lithium ion conductivity, which proves the universality of vacancy-induced rapid ion transport.
Vacancy induced rapid ion transport provides a new idea for the design and development of high-performance ion-conducting membranes. The "Viewpoint" of "Science" in the same period reviewed the work with the topic "Using metal vacancies to accelerate protons".