We report single-atom Cu catalysts dispersed on nitrogen-doped carbon by a nitrogen-coordination strategy. The presence of nitrogen enabled good dispersion and attachment of atomic Cu species on the nitrogen-doped carbon frameworks with Cu−N x configurations. The Cu doping concentrations and Cu−N x configurations were well-tuned by the pyrolysis temperature. At a high Cu concentration of 4.9% mol , the distance between neighboring Cu−N x species was close enough to enable C−C coupling and produce C 2 H 4 . In contrast, at Cu concentrations lower than 2.4% mol , the distance between Cu−N x species was large so that the electrocatalyst favored the formation of CH 4 as C 1 products. Density functional theory calculations further confirmed the capability of producing C 2 H 4 by two CO intermediates binding on two adjacent Cu−N 2 sites, while the isolated Cu−N 4 , the neighboring Cu−N 4 , and the isolated Cu−N 2 sites led to formation of CH 4 . Our work demonstrates a facile approach of tuning active Cu sites for CO 2 electroreduction to different hydrocarbons.

Crystalline mesoporous metal oxides have attracted considerable attention recently, but their catalytic applications have rarely been studied. In this work, a series of crystalline three-dimensional mesoporous metal oxides (i.e., CeO ) were prepared using the mesoporous silica KIT-6 as a hard template. These ordered mesoporous metal oxides with highly crystalline walls were characterized by PXRD, TEM, N 2 adsorption and evaluated as CO oxidation catalysts. These mesoporous materials, except for mesoporous Fe 2 O 3 , exhibit much higher catalytic activities than their bulk counterparts. In particular, mesoporous Co 3 O 4 , b-MnO 2 , and NiO show appreciable CO oxidation activity below 0°C, and the catalytic activities of mesoporous b-MnO 2 , and NiO are even higher than those of their nanoparticulate counterparts with large surface areas. b-MnO 2 is particularly interesting because it combines low cost and low toxicity with high activity (T 50 = 39°C).

The continuous increase of CO2 concentration in the atmosphere has been imposing an imminent threat for global climate change and environmental hazards. In recent years, the electrochemical or photochemical conversion of CO2 into value‐added chemicals or fuels has received significant attention, as it may enable an attractive means to mitigate the atmospheric CO2 concentration and complete the imbalanced carbon‐neutral energy cycle, as well as create renewable energy resources for human use. Among the different electrocatalysts being studied, Cu‐based materials have been demonstrated as the only category of candidates that allows the conversion of CO2 into a variety of reducing products, including carbon monoxide, hydrocarbons, and alcohols. Herein, the reaction pathways for different Cu‐based catalysts for C1 and C2+ products are introduced. Then, different parameters in tuning Cu‐based electrocatalysts are summarized and discussed, including the morphologies, compositions, crystal facets, and oxide derivation. In addition, various types of parameters for CO2 electroreduction are also described, particularly the option of electrolytes such as aqueous, ionic liquids, and organic solutions. Finally, the current challenges are discussed and the potential strategies to facilitate the future development of CO2 electroreduction are summarized.

Cr adsorption on wood-based powdered activated carbon (WPAC) was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The highest Cr(VI) adsorption (40.04%) was obtained under acidic conditions (pH 3), whereas Cr removal at pH 10 was only 0.34%. The mechanism of Cr(VI) removal from aqueous solutions by WPAC was based on the reduction of Cr(VI) to Cr(III) with the concomitant oxidation of C-H and C-OH to C-OH and C=O, respectively, on the surface of WPAC, followed by Cr(III) adsorption. Raman spectroscopy revealed a change in the WPAC structure in terms of the D/G band intensity ratio after Cr(VI) adsorption. SEM-EDS analysis showed that the oxygen/carbon ratio on the WPAC surface increased from 9.85% to 17.74%. This result was confirmed by XPS measurements, which showed that 78.8% of Cr adsorbed on the WPAC surface was in the trivalent state. The amount of oxygen-containing functional groups on the surface increased due to the oxidation of graphitic carbons to C-OH and C=O groups.