Rsearch has shown that nanoscale surface alloys exhibit extraordinary properties in many applications, often greatly outperforming their constituent elements. Despite this, most methods of preparing these materials are either: i) small, well-characterized analytical samples, such as films or single crystals, prepared for structure-function studies, or ii) materials prepared for investigation of applications like catalysis, which are often prepared at large scale by co-precipitation or co-reduction and exhibit compositional heterogeneity. As such, there exists a need for scalable production of nanoscale, bimetallic materials with a high degree of compositional control. Atomic layer electroless deposition (ALED) is a form of surface-limited redox replacement in which a surface hydride layer is chemically formed on a substrate metal, followed by galvanic replacement with an adlayer element. This process can be cycled to yield bimetallic materials of well-defined surface stoichiometry, with arbitrary thickness. Since the process is electroless, it is highly scalable compared to electrochemical deposition. So far, ALED-materials have exhibited atomically thin, conformal adlayers. Herein we demonstrate that, by controlling conditions of deposition, growth mechanism can be altered. Under some conditions, conformal adlayers can be produced, which may be beneficial in uniformly modulating the d-band center at the surface of a catalyst, tuning adsorbate binding energy. Under other conditions, thicker adlayers, having lower fractional coverage, with the same overall stoichiometry can be produced, which may be useful in blocking adsorption of poisoning species or orchestrating “active-sites” with multiple components. We will present spectroscopic and microscopic evidence that ALED is capable of tuning surface morphology between these extremes. Further, we report preparation of bimetallic, nanoporous metals using ALED. The high-surface area of these materials makes other forms of deposition challenging. We demonstrate with microscopy, spectroscopy, and porosimetry, that single and multiple cycles of ALED can be performed on nanoporous Pt without collapsing nanopores or losing surface area.

Scalable preparation of nanoscale, bimetallic materials with precisely controlled surface composition and tunable surface morphology

256th National Meeting (2018)

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