Coordination and interface engineering to boost catalytic property of two-dimensional ZIFs for wearable Zn-air batteries

Metal organic frameworks(MOFs) have been considered as compelling precursor for miscellaneous applications. However, their unsatisfied electrocatalytic performance limits their direct application as electrocatalyst. Herein, by incorporating the cobalt-oxide bonds and polyaniline(PANI) with two-dimension zeolitic imidazolate frameworks(ZIFs), a novel bifunctional catalyst(Co-O-ZIF/PANI) for Zn-air battery was designed based on a facile and eco-friendly method. This Co-O-ZIF/PANI with optimized surface adsorption effect and suitable Co^(3+)/Co^(2+)ratio, exhibits eminent electrocatalytic activity toward both oxygen reduction and evolution reaction. The as-assembled liquid ZABs based on Co-O-ZIF/PANI achieves a remarkable maximum power density of 123.1 m W cm^(-2) and low discharge-charge voltage gap of 0.81 V at 5 m A cm^(-2) for over 300 cycles. Operando Raman spectroscopy reveals that the excellent performance origins from the optimized surface chemisorption property of O_(2) and H_(2)O brought by Co–O bonds and PANI. This work provides a novel prospect to develop efficient MOF derived bifunctional electrocatalysts by optimizing surface chemisorption properties.

Density and structure of undercooled liquid titanium

For liquid Ti, it is difficult to achieve high undercooling because of its chemical reactivity; as a result, there is little information available on its properties and structure in the undercooled state. In this study, we investigate the density and structure, using molecular dynamics method, for the undercooling and superheating ranges 0-743 K and 0-457 K. The density increases quadratically for undercooling. At the melting temperature, the density is 4.14 g/cm3, and first and second temperature coefficients are obtained. The pair correlation functions and coordination numbers indicate that the short range degree of order becomes increasingly significant with increasing undercooling.