(489a) Nobel Metal Ion-Directed Assembly of 2D Materials for Synergistic Photocatalysts and Noble Metal Structuring

Assembling 2D-material nanosheets into micro- and macro-scale structures with augmented functions continues to be a critical challenge confronted by industry and academia. External spacers and binders are generally required to assemble the 2D-material nanosheets yet inevitably sacrifice the intrinsic properties of 2D materials, failing to induce synergistic functions. Metal ions serve as a branch of moderate/reversible ionic binders aligning the sheets of 2D materials Alkali earth metals and other accessible transition metals have been explored however, they remain monofunctional once the material is aligned. Noble metal ions feature a range of sizes and exhibit electrostatic interactions with diverse 2D materials, thus facilitating the self- or direct assembly of 2D materials into 3D structures. Furthermore, the complexed noble metal ions can be thermally reduced in situ within the interlayer spacings of assembled 2D materials, enabling the synthesis of noble metal–2D material structures with proven potential in catalytic reactions. Herein, we first conduct a series of zeta potential measurements to examine the colloidal stability of various noble metal ion–2D material matches. The electric potential at the slipping plane gives insight on the adsorption of ionic species onto the 2D materials. Depending on the colloidal solutions stability, the respective noble metal ion-2D material pair was developed into either 2D material aerogels (low stability) or noble metal ion inks (moderate stability). To fabricate the 2D-material aerogels, a graphene oxide (GO) crumple-texture was created and analyzed. A GO crumple analysis and 3D scanning were performed to give insight to optimize the consistency of the obtained crumpling and to maximize the noble metal ion volume that the crumple structure can retain. Using the GO crumple-textured platform, various gels were created with varying degrees of cross-linking. The noble metal ions containing amine ligands (such as tetraammineplatinum(II) nitrate) serve as ideal covalent crosslinkers, with the highest storage modulus, to direct the gelation of 2D-material nanosheets. Followed by freeze-drying and thermal in situ reduction, various platinum and ruthenium-decorated 2D material aerogels are produced containing an optimized high surface area and moderate particle size. In tandem with GO-crumple textures, the noble metal aerogels act as synergistic photocatalysts for ammonia formation owing to the observed high thermal conductivity and light absorbing properties. On the other hand, the noble metal ions in high ionic strength suspensions (such as platinum(IV) chloride) can assemble with 2D-material nanosheets, generating electrostatically & entropically stable, printable "metalized inks". The "metalized inks" can be applied to fabricate various noble metal structures with accurate control of metal loading, grain size/porosity, composition, and micro/nanomorphologies.