Bimetallic Cu-Fe catalysts on MXene for synergistically electrocatalytic conversion of nitrate to ammonia.

NO3- is a common water pollutant that can serve as a potential nitrogen source for electrocatalytic NH3 production. However, an efficient and complete removal of low NO3- concentrations remains a challenge. Fe1Cu2@MXene bimetallic catalysts were constructed on two-dimensional Ti3C2Tx MXene carriers via a simple solution-based synthetic method and used for the electrocatalytic reduction of NO3-. The combination of the rich functional groups, high electronic conductivity on the MXene surface, and the synergistic effect between the Cu and Fe sites enabled the composite to effectively catalyse NH3 synthesis, with a 98% conversion of NO3- in 8 h and a selectivity for NH3 of up to 99.6%. In addition, Fe1Cu2@MXene showed excellent environmental and cyclic stability at various pH values and temperatures over multiple (14) cycles. Semiconductor analysis techniques and electrochemical impedance spectroscopy confirmed that the synergistic effect provided by the dual active sites of the bimetallic catalyst enabled fast electron transport. This study provides new insights into the synergistic promotion of NO3- reduction reactions using bimetals.

Coordination Chemistry Dictates the Structural Defects in Lead Halide Perovskites.

We show the influence of species present in precursor solution during formation of lead halide perovskite materials on the structural defects of the films. The coordination of lead by competing solvent molecules and iodide ions dictate the type of complexes present in the films. Depending on the processing conditions all PbIS5 (+) , PbI2 S4, PbI3 S3 (-) , PbI4 S2 (2-) , PbI5 S2 (3-) , PbI6 (4-) and 1D (Pb2 I4 )n chains are observed by absorption measurements. Different parameters are studied such as polarity of the solvent, concentration of iodide ions, concentration of solvent molecules and temperature. It is concluded that strongly coordinating solvents will preferentially form species with a low number of iodide ions and less coordinative solvents generate high concentration of PbI6 (-) . We furthermore propose that all these plumbate ions may act as structural defects determining electronic properties of the photovoltaic films.