Selective and efficient catalytic conversion of carbon dioxide (CO2) into value-added fuels and feedstocks provides an ideal avenue to high-density renewable energy storage. An impediment to enabling deep CO2 reduction to oxygenates and hydrocarbons (e.g., C2+ compounds) is the difficulty of coupling carbon-carbon bonds efficiently. Copper in the +1 oxidation state has been thought to be active for catalyzing C2+ formation, whereas it is prone to being reduced to Cu0 at cathodic potentials. Here we report that catalysts with nanocavities can confine carbon intermediates formed in situ, which in turn covers the local catalyst surface and thereby stabilizes Cu+ species. Experimental measurements on multihollow cuprous oxide catalyst exhibit a C2+ Faradaic efficiency of 75.2 ± 2.7% at a C2+ partial current density of 267 ± 13 mA cm-2 and a large C2+-to-C1 ratio of ∼7.2. Operando Raman spectra, in conjunction with X-ray absorption studies, confirm that Cu+ species in the as-designed catalyst are well retained during CO2 reduction, which leads to the marked C2+ selectivity at a large conversion rate.

Protecting Copper Oxidation State via Intermediate Confinement for Selective CO2 Electroreduction to C2+ Fuels.

Spectroscopic properties of semiconductor crystals with direct forbidden energy gap

The cyclotron resonance of electrons and of holes in Cu2O has been observed between 1.2 and 20K using frequencies of 34 and 137 GHz. Electrons have an isotropic polaron mass of (0.99+or-0.03)m0 where m0 is the mass of the free electron. Holes have isotropic polaron masses of (0.58+or-0.03)m0 and (0.69+or-0.04)m0, the error bars defining the points of half-height on the observed resonance curves. The authors attribute the electron resonance to the lowest Gamma 1+( Gamma 6+) minimum of the conduction band and the heavier hole to the uppermost Gamma 7+ hole band. The lighter hole is attributed tentatively to the Gamma 8+ maximum of the hole band. The exciton spectra of Cu2O are discussed in terms of these masses.

https://iopscience.iop.org/article/10.1088/0022-3719/9/8/014/pdf

Cyclotron resonance of electrons and of holes in cuprous oxide, Cu2O

Cuprous oxide (Cu 2 O) thin films prepared by reactive d.c. sputtering technique

Cu2O thin films were grown on sapphire (0001) and MgO (100) substrates by chemical vapor deposition. The crystalline, vibrational and electrical properties of the layers and the amount of incorporated background impurities have been examined. X-ray diffraction measurements revealed, that the polycrystalline films grew in (111) and (100) orientation on sapphire and in (100) orientation on MgO. Raman measurements indicated the presence of CuO inclusions in the films. The electrical properties are dominated by an acceptor level located 150 meV above the valence band. This level may originate from unintentionally incorporated silicon impurities.

Copper oxide thin films by chemical vapor deposition: Synthesis, characterization and electrical properties

Resonance Raman scattering in Cu2O at the blue and indigo excitons

A study of non-thermalized luminescence spectra: the case of Cu2O

https://escholarship.org/content/qt49b5q2nv/qt49b5q2nv.pdf?t=p0uvtw

P.Y. Yu

Papers

Resonance Raman scattering in Cu2O at the blue and indigo excitons

A study of non-thermalized luminescence spectra: the case of Cu2O

Resonant Raman scattering by two LO phonons in InSb at the E1 transition