The electrochemical reduction of CO to syngas with a tunable CO/H ratio is regarded as an economical and promising method for the future. Herein, a series of earth-abundant Zn catalysts with different crystal facet ratios of Zn(002) to Zn(101) in the bulk phase have been prepared on electrochemically polished Cu foam by the electrochemical deposition method. The Zn catalyst with more (101) crystal facets show good electrochemical activity for the CO reduction reaction (CORR) to CO and that with more (002) crystal facets favor the hydrogen evolution reaction. The linear relationship between the crystal facet ratio of Zn(101) to Zn(002) and the Faradaic efficiency (FE) of CORR to CO has been revealed for the first time. The prepared catalyst with more (101) facets show greater than 85% FE to syngas at -0.9 V (vs reversible hydrogen electrode) in aqueous electrolyte, with tunable CO/H ratios ranging from 0.2 to 2.31 that can be used in existing industrial systems. Meanwhile, the mechanism of electroreduction of CO on the Zn electrode has been studied by in situ infrared absorption spectroscopy. The highly selective role of the Zn(101) crystal facet in the CORR to CO has been evidenced by density functional theory calculations.

Nitrogen dopants on carbon materials play vital roles in metal-free carbon catalysis, while the role of pyridinic nitrogen (N P ) or graphitic nitrogen (N G ) is still on debate. In this work, N-doped carbon nanotubes were employed to catalyze the oxidation of styrene (SOR) with tert-butyl hydroperoxide as oxidant. We observed a significant enhancement of SOR activity caused by the incorporation of nitrogen dopants when the N content was lower than 3.51% but a decline of activity at higher N contents. At N content up to 7.51%, even worse performance than that on N-doped carbon nanotubes with 0.98% N content was observed. This behavior was rationalized by thorough density functional theory calculations. Different catalytic functions of N P and N G were revealed. More significantly, a synergistic effect between N P and N G was demonstrated when they are quite close, which is unbeneficial for the catalytic activity due to the very high energy barriers. The finding may pave a way to the rational design of high-performance metal-free carbon catalysts.

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The coordination of cyclic β-D-glucose (CDG) to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](1+) ions has been theoretically investigated, using quantum chemical calculations at the PBE0/6-311++G(d,p), aug-cc-pvtz level under polarizable continuum model IEF-PCM, and molecular dynamics simulations. [Al(OH)(aq)](2+) ion prefers to form both six- and five-coordination complexes, and [Al(OH)2(aq)](+) ion to form four-coordination complex. The two kinds of oxygen atoms (on hydroxyl and ring) of CDG can coordinate to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](+) ions through single-O-ligand and double-O-ligand coordination, wherein there exists some negative charge transfer from the lone pair electron on 2p orbital of the coordinated oxygen atom to the empty 3s orbital of aluminum atom. The charge transfer from both the polarization and H-bond effects stabilizes the coordinated complex. When the CDG coordinates to both [Al(OH)(H2O)4](2+) and [Al(OH)2(H2O)2](1+) ions, the exchange of water with CDG would take place. The six-coordination complex [(ηO4,O6(2)-CDG)Al(OH)(H2O)3](2+) and the five-coordination complex [(ηO4,O6(2)-CDG)Al(OH)2(H2O)](1+) are predicted to be the thermodynamically most preferable, in which the polarization effect plays a crucial role. The molecular dynamics simulations testify the exchange of water with CDG, and then support a five-coordination complex [(ηO4,O6(2)-CDG)Al(OH)2(H2O)](1+) as the predominant form of the CDG coordination to [Al(OH)2(aq)](1+) ion.

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