Unlocking the Potential of Colloidal Quantum Dot/Organic Hybrid Solar Cells: Band Tunable Interfacial Layer Approach.

Hybrid colloidal quantum dot (CQD)/organic architectures are promising candidates for emerging optoelectronic devices having high performance and inexpensive fabrication. For unlocking the potential of CQD/organic hybrid devices, enhancing charge extraction properties at electron transport layer (ETL)/CQD interfaces is crucial. Hence, we carefully adjust the interface properties between the ETL and CQD layer by incorporating an interfacial layer for the ETL (EIL) using several types of cinnamic acid ligands. The EIL having a cascading band offset (ΔEC) between the ETL and CQD layer suppresses the potential barrier and the local charge accumulation at ETL/CQD interfaces, thereby reducing the bimolecular recombination. An optimal EIL effectively expands the depletion region that facilitates charge extraction between the ETL and CQD layer while preventing the formation of shallow traps. Representative devices with an EIL exhibit a maximum power conversion efficiency of 14.01% and retain over 80% of initial performances after 300 h under continuous maximum power point operation.

Tuning the C1 /C2 Selectivity of Electrochemical CO2 Reduction on Cu-CeO2 Nanorods by Oxidation State Control.

Ceria (CeO2 ) is one of the most extensively used rare earth oxides. Recently, it has been used as a support material for metal catalysts for electrochemical energy conversion. However, to date, the nature of metal/CeO2 interfaces and their impact on electrochemical processes remains unclear. Here, a Cu-CeO2 nanorod electrochemical CO2 reduction catalyst is presented. Using operando analysis and computational techniques, it is found that, on the application of a reductive electrochemical potential, Cu undergoes an abrupt change in solubility in the ceria matrix converting from less stable randomly dissolved single atomic Cu2+ ions to (Cu0 ,Cu1+ ) nanoclusters. Unlike single atomic Cu, which produces C1 products as the main product during electrochemical CO2 reduction, the coexistence of (Cu0 ,Cu1+ ) clusters lowers the energy barrier for C-C coupling and enables the selective production of C2+ hydrocarbons. As a result, the coexistence of (Cu0 ,Cu1+ ) in the clusters at the Cu-ceria interface results in a C2+ partial current density/unit Cu weight 27 times that of a corresponding Cu-carbon catalyst under the same conditions.

Tunable Product Selectivity in Electrochemical CO2 Reduction on Well-Mixed Ni-Cu Alloys.

Electrochemical reduction of CO2 on copper-based catalysts has become a promising strategy to mitigate greenhouse gas emissions and gain valuable chemicals and fuels. Unfortunately, however, the generally low product selectivity of the process decreases the industrial competitiveness compared to the established large-scale chemical processes. Here, we present random solid solution Cu1-xNix alloy catalysts that, due to their full miscibility, enable a systematic modulation of adsorption energies. In particular, we find that these catalysts lead to an increase of hydrogen evolution with the Ni content, which correlates with a significant increase of the selectivity for methane formation relative to C2 products such as ethylene and ethanol. From experimental and theoretical insights, we find the increased hydrogen atom coverage to facilitate Langmuir-Hinshelwood-like hydrogenation of surface intermediates, giving an impressive almost 2 orders of magnitude increase in the CH4 to C2H4 + C2H5OH selectivity on Cu0.87Ni0.13 at -300 mA cm-2. This study provides important insights and design concepts for the tunability of product selectivity for electrochemical CO2 reduction that will help to pave the way toward industrially competitive electrocatalyst materials.

Quasi-graphitic carbon shell-induced Cu confinement promotes electrocatalytic CO2 reduction toward C2+ products.

For steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas-solid reaction governed by the CO (g) - CO2 (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO2 reduction reaction and provided a platform for rational material design. C2+ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C2H4 at -0.55 V (vs RHE) and a C2H4 cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C2+ selectivity of 82.3% at a partial current density of 329.2 mA/cm2 was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO2-to-C2H4 conversion over 180 h and allow practical application of electrocatalysts for renewable energy conversion.