Nature has developed unique strategies to refine and optimise structural performance. Using surfaces designed at multiple length scales, from micro to nano levels, combined with complex chemistries, different natural organisms can exhibit similar wetting but different adhesion to liquids under specific environments. These biological surfaces have inspired researchers to develop new approaches to control surface wetting and liquid behaviour via surface adhesion. Here we review natural strategies to control the interaction of liquids with solid surfaces and the efforts to implement these strategies in synthetic materials designed to work in either atmospheric or underwater environment. Particular attention is paid to droplet behaviour on the special-adhesion surfaces in nature and artificial smart surfaces. We highlight recent progress, identify the common threads, and discuss the fundamental differences in a way that can help formulate rational approaches towards surface engineering, and identify current challenges as well as future directions for the field.
The conversion of ethylene to ethylidyne on Rh(111) is examined using self-consistent periodic density function theory. The adsorptions of the reactants, intermediates, and products involved as well as the thermodynamics and kinetics of the conversion are characterized. Ethylene could form two adsorption configurations designated as di-σ and π adsorptions on Rh(111); ethyl, vinyl, vinylidene, ethylidyne, and ethylidene prefer the saturated sp3 configuration of both carbon atoms with the lost H atoms replaced by the metal atoms. The three-step conversion path on Rh(111), i.e., ethylene → vinyl → vinylidene → ethylidyne, is the most feasible, in which the vinylidene hydrogenation is the rate-limiting step. The pathway through ethylidene intermediate, ethylene → vinyl → ethylidene → ethylidyne, is impractical because it has a conversion rate at least 104 times lower than the most favorable path at the real reaction conditions. The mechanism via ethyl intermediate, ethylene → ethyl → ethylidene → ethylidyne, is impossible because of the high dehydrogenation barrier of ethyl to ethylidene as well as the low barriers for the conversions of ethyl to ethane and/or ethylene. Conversion involving direct isomerizations is also unlikely to be important due to the very high energy barriers involved.
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