Intrinsic defects and free volume in hollow Cu3N nanocatalysts for CO2 reduction

Electrochemical reduction of CO2 is a route for environmental sustainability because it removes excessive CO2 from the air and produces high added value multi-carbon products. Recently, Cu3N has emerged as a promising electrocatalyst for the electrochemical reduction of CO2 and for photocatalityc evolution of H2. In contrast to conventional wet chemistry that uses aggressive chemicals and high temperatures in multiple steps, we developed an environmentally benign, one-step method that involves reactive magnetron sputtering of Cu in naturally abundant N2 in the configuration of a gas aggregation cluster source to produce nanoparticles(NPs) of Cu3N in the gas phase, avoiding hazardous chemistry and high temperatures. The Cu3N NPs can be deposited in multilayers on solid supports, and the first tests showed that they successfully convert CO2. HR-TEM analysis revealed that Cu3N NPs have a hollow structure and contain crystallographic defects, the latter may or may not be critical to the catalytic performance of these NPs, as Cu3N is known to have a defect-tolerant electronic structure, which means that Cu3N maintains its properties regardless of the presence or absence of crystallographic defects. Nevertheless, the influence of these peculiarities on the resultant catalytic efficiency of our Cu3N NPs is not known. We propose to use Positron Annihilation Lifetime Spectroscopy (PALS) to investigate the concentration of defects/vacancies and GiSAXS/GiWAXS to study the crystalline structure of the Cu3N NPs. This information will help us to elucidate the electrochemical activity of these Cu3N NPs in terms of CO2 reduction.