Abstract
Earth-abundant transition metal phosphides are promising materials for energy-related applications. Specifically, copper(I) phosphide is such a material and shows excellent photocatalytic activity. Currently, there are substantial research efforts to synthesize well-defined metal–semiconductor nanoparticle heterostructures to enhance the photocatalytic performance by an efficient separation of charge carriers. The involved crystal facets and heterointerfaces have a major impact on the efficiency of a heterostructured photocatalyst, which points out the importance of synthesizing potential photocatalysts in a controlled manner and characterizing their structural and morphological properties in detail. In this study, we investigated the interface dynamics occurring around the synthesis of Ag–Cu3P nanoparticle heterostructures by a chemical reaction between Ag–Cu nanoparticle heterostructures and phosphine in an environmental transmission electron microscope. The major product of the Cu–Cu3P phase transformation using Ag–Cu nanoparticle heterostructures with a defined interface as a template preserved the initially present Ag{111} facet of the heterointerface. After the complete transformation, corner truncation of the faceted Cu3P phase led to a physical transformation of the nanoparticle heterostructure. In some cases, the structural rearrangement toward an energetically more favorable heterointerface has been observed and analyzed in detail at the atomic level. The herein-reported results will help better understand dynamic processes in Ag–Cu3P nanoparticle heterostructures and enable facet-engineered surface and heterointerface design to tailor their physical properties.
Highlights
We investigated the interface dynamics occurring around the synthesis of Ag−Cu3P nanoparticle heterostructures by a chemical reaction between Ag−Cu nanoparticle heterostructures and phosphine in an environmental transmission electron microscope
For the formation of Ag−Cu3P nanoparticle heterostructures, bimetallic Ag−Cu nanoparticles were generated in a spark ablation system,[55] and particles with a defined diameter of 30 nm were selected via an integrated filtering system for the deposition on a microelectromechanical systems (MEMS)-based heating chip for in situ transmission electron microscopy (TEM) investigations
The chip was transferred to an environmental transmission electron microscope (ETEM) with an integrated metal−organic chemical vapor deposition (MOCVD) system
Summary
Over the last years, nanostructured transition metal phosphides (TMPs) have been the focus of several research efforts due to their excellent performance in energy-related applications, including electrocatalysis, photocatalysis, and energy storage.[1]. Most of the targeted TMPs with high potential in this research field are earth-abundant and could become a cost-efficient and sustainable alternative compared to widely used noble metals.[2−4] Copper(I) phosphide (Cu3P), which is the focus of this work, is a p-type semiconductor with a bandgap of ∼1.50 eV.[5−7] The p-type semiconducting behavior of Cu3P has its origin in the pronounced substoichiometry in Cu due to Cu vacancies, which has already been discussed in detail in previous studies.[8,9] A homogeneity range between approximately Cu2.9P and Cu2.3P has been reported,[10] making the use of the chemical formula Cu3−xP more appropriate, and theoretical calculations suggest an increase of Cu vacancies with temperature.[8] Since we did not study the composition in detail, we will refer to Cu3−xP as Cu3P for simplicity.
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