TY - JOUR

T1 - Creating Directionality in Nanoporous Carbon Materials: Adjustable Combinations of Structural and Chemical Gradients

AU - Bahner, Jochen

AU - Klinkenberg, Nele

AU - Frisch, Marvin

AU - Brauchle, Lilly

AU - Polarz, Sebastian

N1 - Funding Information: The authors thank the Carl-Zeiss foundation for funding of J.B. by a PhD scholarship. The authors gratefully acknowledge technical/instrumental support from the German Research Foundation (DFG) via SFB1214 Project Z1 Particle Analysis Center. The authors gratefully acknowledge instrumental support from the Electron Microscopy Centre of the University of Konstanz.

PY - 2019/10/29

Y1 - 2019/10/29

N2 - The properties of porous materials benefit from hierarchical porosity. A less noted element of hierarchy is the occurrence of directionality in functional gradient materials. A sharp boundary is replaced by a transition from one feature to the next. The number of cases known for porous materials with either structural or chemical gradients is small. A method capable of generating combinations of structural and chemical gradients in one material does not exist. Such a method is presented with a focus on silver and nitrogen containing carbon materials because of the potential of this system for electrocatalytic CO 2 reduction. A structural gradient results from controlled separation using ultracentrifugation of a binary mixture of template particles in a resorcinol–formaldehyde (RF) sol as carbon precursor. A new level of complexity can be reached, if the surfaces of the template particles are chemically modified. Although the template is removed during carbonization, the modification (Ag, N) becomes integrated into the material. Understanding how modified and unmodified large and small particles sediment in the RF sol enables almost infinite variability of combinations: chemically graded but structurally homogeneous materials and vice versa. Ultimately, a material containing one structural gradient and two chemical gradients with opposing directions is introduced.

AB - The properties of porous materials benefit from hierarchical porosity. A less noted element of hierarchy is the occurrence of directionality in functional gradient materials. A sharp boundary is replaced by a transition from one feature to the next. The number of cases known for porous materials with either structural or chemical gradients is small. A method capable of generating combinations of structural and chemical gradients in one material does not exist. Such a method is presented with a focus on silver and nitrogen containing carbon materials because of the potential of this system for electrocatalytic CO 2 reduction. A structural gradient results from controlled separation using ultracentrifugation of a binary mixture of template particles in a resorcinol–formaldehyde (RF) sol as carbon precursor. A new level of complexity can be reached, if the surfaces of the template particles are chemically modified. Although the template is removed during carbonization, the modification (Ag, N) becomes integrated into the material. Understanding how modified and unmodified large and small particles sediment in the RF sol enables almost infinite variability of combinations: chemically graded but structurally homogeneous materials and vice versa. Ultimately, a material containing one structural gradient and two chemical gradients with opposing directions is introduced.

KW - aerogels

KW - functional gradient materials

KW - hierarchical porosity

KW - surface modification

KW - templates

UR - http://www.scopus.com/inward/record.url?scp=85071356998&partnerID=8YFLogxK

U2 - 10.1002/adfm.201904058

DO - 10.1002/adfm.201904058

M3 - Article

VL - 29

JO - Advanced functional materials

JF - Advanced functional materials

SN - 1616-301X

IS - 44

M1 - 1904058

ER -