Efficiently Enhanced Selectivity of Electrocatalyzing Ethanol to High Value-Added Acetaldehyde Through Tuning the Cobalt Valence State

Using electrochemical oxidation of alcohols to substitute the oxygen evolution reaction is beneficial to reduce the energy consumption of hydrogen production. Converting alcohols into high value-added products with high efficiency and selectivity by designing a proper electrocatalyst is economical and has promising applications. In this work, two types of spinel cubic phase Co3O4 with different contents of oxygen vacancies were obtained by annealing the same precursor in air and argon gas atmosphere, respectively. The results of X-ray photoelectron spectroscopy and in situ Raman spectra reveal that abundant Co4+ sites were formed on the surface of Co3O4–air under the electrocatalysis condition, while main Co3+ sites were formed on the surface of Co3O4–Ar. The electrocatalytic ethanol oxidation tests and density functional theory calculation reveal that the Co4+ sites exhibit more proper adsorption energy to the O*CCH3 intermediate, which benefits the formation of high-value-added acetaldehyde products instead of common acetic acid products with a higher degree of oxidation. The Faradaic efficiency of the Co3O4–air catalyst to acetaldehyde achieves 60.02%, and the selectivity to acetaldehyde reaches 79.63% at an oxidation overpotential of 1.46 V. This work provides the possibility and guidance for electrochemical oxidation of alcohols into high value-added products

Atomically Thin Zn₂GeO₄ Nanoribbons: Facile Synthesis and Selective Photocatalytic CO₂ Reduction toward CO

Atomically thin Zn2GeO4 (ZGO) nanoribbons exclusively exposing the {100} facet of ∼1 nm in thickness were successfully prepared via convenient photo-oxidation exfoliation of the ZGO–ethylenediamine hybrid at room temperature. The ultrathin ZGO nanoribbons [abbreviated as ZGO(100)] exhibit efficient and dominantly selective CO2 photoreduction performance into CO with the evolution yield of up to 20.81 μmol g–1 h–1 in the presence of water vapor, in much contrast to only CH4 production of 0.67 μmol g–1 h–1 for (010), exposing the thick ZGO nanobelts reported previously. The atomically thin structure of ZGO(100) shortens the migration distance of charge carriers onto the surface from the interior and allows more electrons to survive and accumulate on the surface, thus benefiting the activation and reduction of CO2. The density function theory calculation reveals that the formed CO* is inclined to escape from the exclusively exposed {100} facet of the ultrathin ZGO nanoribbon rather than be further protonated to derive CHO*, a vital intermediate for CH4 formation, leading ZGO(100) to be an ideal platform for catalytically selective CO production. This work would not only enrich atomically thin catalyst materials but also render a new platform for the development of ternary semiconductors with outstanding performance in CO2 photoconversion