In situ deposited copper nanodendrites are herein proven to be a highly selective electrocatalyst which is capable of reducing CO2 to ethylene by reaching a Faradaic efficiency of 57% at a current density of 170 mA cm−2. It is found that the desired structures are formed in situ under acidic pH conditions at high electrode potentials more negative than −2 V versus Ag/AgCl. Detailed investigations on the preparation, characterization, and advancement of electrode materials and of the electrolyte have been performed. Catalyst degradation effects are intensively followed by scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HR‐TEM) characterization methods and found to be a major root course for selectivity losses.

A copper‐oxide‐based catalyst enriched with paramelaconite (Cu4O3) is presented and investigated as an electrocatalyst for facilitating electroreduction of CO2 to ethylene and other hydrocarbons. Cu4O3 is a member of the copper‐oxide family and possesses an intriguing mixed‐valance nature, incorporating an equal number of Cu+ and Cu2+ ions in its crystal structure. The material is synthesized using a solvothermal synthesis route and its structure is confirmed via powder X‐ray diffraction, transmission electron microscope based selected area electron diffraction, and X‐ray photoelectron spectroscopy. A flow reactor equipped with a gas diffusion electrode is utilized to test a copper‐based catalyst enriched with the Cu4O3 phase under CO2 reduction conditions. The Cu4O3‐rich catalyst (PrC) shows a Faradaic efficiency for ethylene over 40% at 400 mA cm−2. At −0.64 versus reversible hydrogen electrode, the highest C2+/C1 product ratio of 4.8 is achieved, with C2+ Faradaic efficiency over 61%. Additionally, the catalyst exhibits a stable performance for 24 h at a constant current density of 200 mA cm−2.

No abstract

No abstract

Focus of this work is the optimization of growth to achieve high quality laser material for emission at 1.3 mm and beyond. GaAs/GaAsN/InGaAsN heterostructures were grown by solid source molecular beam epitaxy. To achieve optimum crystal quality of InGaAsN heterostructures, growth was followed by a high temperature treatment at about 7008C. The high optical quality of our annealed material is attested by large exciton recombination lifetimes (more than 2 ns). Consequently, a decrease of single quantum well transparency current density down to 100 A/cm 2 is found and SWQ lasers with threshold current densities as low as 350 A/cm 2 have been made. This represents clearly the lowest laser thresholds reported so far for emission around 1.3 mm from the InGaAsN material system.