Adsorbed atomic H (H*) facilitates indirect pathways playing a major role in the electrochemical removal of various priority pollutants. It is crucial to identify the atomic sites responsible for the provision of H*. Herein, through a systematic study of the distribution of H* on Pd nanocatalysts with different sizes and, more importantly, deliberately controlled relative abundance of surface defects, we uncovered the central role of defects in the provision of H*. Specifically, the H* generated on Pd in an electrochemical process increased markedly upon introducing defect sites by changing the morphology to ultrathin polycrystalline Pd nanowires (NWs), while dramatically reducing upon decreasing the number of surface defects through an annealing treatment. Benefiting from a proportion of H* up to 40% of the total H* species, the Pd NWs showed an electrochemical active surface area normalized rate constant of 13.8 ± 0.8 h m, which is 8-9 times higher than its Pd/C counterparts. The pivotal role of defect sites for the generation of H* was further verified by blocking such sites with Rh and Pt atoms, while theoretical calculation also confirms that the adsorption energy of H* on these sites is much higher than that on the Pd{111} facet.

Mythology? Reality? Innovative technologies have achieved the conversion and storage of renewable energies as the hero did in Chinese myths.

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RbSbSO4Cl2 exhibits a strong SHG response originating from the synergistic effect of three coexisting constituting asymmetric chromophores.

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The development of rational pharmaceutical polymorph control systems from crystallization requires the experimental manipulation of both thermodynamic and kinetic factors. Herein, we discuss the interplay between thermodynamics and kinetics on the formation mechanism responsible for concomitant polymorphs and their subsequent phase transformations. The polymorphic system studied is gestodene, which exhibits two enantiotropic polymorphs, I and II. The thermodynamic stability in ethanol is I > II above 18.5 °C and I < II below. At low supersaturation (1.09 to 1.25), plate-like crystals corresponding to form I become the dominant polymorph at T ≥ 19 °C, while at T ≤ 17 °C, needle-like solids corresponding to form II predominate. Solution crystallization at 5 ≤ T ≤ 25 °C and high supersaturation (1.36 to 1.81) results in concomitant polymorphs of forms I and II. The assessments of nucleation and growth kinetics indicate that at lower supersaturations, both nucleation and growth rates of the stable form are higher than that of the metastable one, while at higher supersaturations, the reverse occurs. It is therefore concluded that at lower supersaturations the stable form is favored by both thermodynamics and kinetics and at higher supersaturations concomitant polymorphism is the result of a balance between these competing driving forces. A semiempirical model that displays the influence of initial supersaturation and crystallization temperature on the relative nucleation rate of the two forms was derived and could be used to predict the polymorphic form resulting from nucleation with good accuracy. As the solvent-mediated polymorphic transformation kinetics between forms I and II is relatively fast at 5, 10, 30, and 35 °C, it can reasonably be expected that one can use a slurrying procedure to obtain the pure stable form when concomitant polymorphs appear at conditions of relatively high supersaturations.

The aim of this study was to prepare manganese dioxide with different crystal forms through hydrothermal

The cooperative effects of the lone pair and cation size were used to tune the symmetry of two stoichiometrically equivalent compounds, A2SO4·(SbF3)2 (A = K or Rb).