Three-Dimensional Hierarchical Copper-Based Nanostructures as Advanced Electrocatalysts for CO₂ Reduction

Cu-based nanomaterials have received increasing interest for electrocatalytic applications in the CO₂ reduction reaction. However, it is challenging to design nanostructured Cu electrodes to improve both the chemical kinetics and molecular transport under the reaction conditions. Here we report on a new type of three-dimensional Cu-based nanostructures as advanced electrocatalysts for CO₂ reduction. Driven by thermal oxidation, CuO nanowires and/or porous nanostructures are grown on commercial Cu foams with three-dimensional (3D) frameworks. An electrochemical method is used to reduce CuO to Cu with the structural features largely preserved. The derived Cu-based hierarchical nanostructures demonstrate high catalytic activity and selectivity for CO₂ reduction, achieving >80% Faradaic efficiency and ∼3 times enhancement in terms of CO₂ conversion rate as compared to the Cu nanowires grown on planar electrodes. Our work highlights the great potential of 3D Cu nanostructures for improving the energy efficiency and power performance of CO₂ electrolysis

Polynorbornene Copolymer with Side-Chain Iridium(III) Emitters and Carbazole Hosts: A Single Emissive Layer Material for Highly Efficient Electrophosphorescent Devices

Vinyl addition copolymerization of norbornene monomers using a Pd­(II) catalyst in combination with 1-octene chain transfer agent efficiently produces well-defined soluble polynorbornene copolymers bearing side-chain (C^∧N)₂Ir­(O^∧O) emitters (C^∧N = 2-(4,6-difluorophenyl)-pyridine (<b>M</b>_<b>3</b>); 2-phenyl-pyridine (<b>M</b>_<b>4</b>); 2-(benzo­[<i>b</i>]­thiophen-2-yl)-pyridine (<b>M</b>_<b>5</b>), O^∧O = acetylacetonato) and 9,9′-(1,3-phenylene)­bis-9<i>H</i>-carbazole (mCP) or 9,9′-(1,1′-biphenyl)-4,4′-diylbis-9<i>H</i>-carbazole (CBP) host moieties (<b>M</b>_<b>1</b> and <b>M</b>_<b>2</b>). The catalytic system provides high-molecular-weight copolymers (<i>M</i>_w = 151 000–457 000 g/mol) with a controlled incorporation of monomers. All copolymers possess high thermal stability with high decomposition (<i>T</i>_d5 > 400 °C) and glass transition temperatures (<i>T</i>_g > 330 °C). Among the solution-processed devices fabricated based on a single emissive layer comprising the blue-, green-, and red-phosphorescent copolymers (<b>PBn</b>, <b>PGn</b>, and <b>PRn</b>, <i>n</i> = 1–4) with various concentrations of emitters (1.7–13.9 mol %-Ir), the devices based on <b>PB4</b> (10.5 mol %-Ir), <b>PG2</b> (5.3 mol %-Ir), and <b>PR4</b> (13.9 mol %-Ir) display the best performances with maximum power efficiencies of 12.9, 25.6, and 3.3 lm/W and maximum external quantum efficiencies of 8.8, 13.3, and 5.1%, respectively, for each color. These results correspond to almost double the efficiencies of the corresponding doped polymer systems and are outstanding among the polymeric rivals reported thus far