Janus to Core–Shell to Janus: Facile Cation Movement in Cu_2–xS/Ag₂S Hexagonal Nanoplates Induced by Surface Strain Control

Abstract

Nanocrystals with multiple compositions and heterointerfaces have received great attention due to promising multifunctional and synergistic physicochemical properties. In particular, heterointerfaces have been at the focal point of nanocatalyst research because the strain caused by lattice mismatches between different phases is the dominant determinant of surface energy and catalytic activity. The ensemble effects of different material phases have also contributed to the interest in heterointerfaced multicomponent materials. Until now, heterointerfaces have largely been regarded as static, and the dynamic movement of components within the multicomponent material phases has received little attention, although the dynamic movement of individual components within multicomponent materials can revise the interpretation of the catalytic behaviors of these materials and lead to fascinating opportunities for nanostructure synthesis. In this study, we demonstrate unprecedented cation migrations within a sulfide matrix induced by surface strain modulation initiated by cation exchange. Specifically, Cu and Ag cations in the sulfide matrix were initially segregated to form a Janus structure. This Janus configuration was then transformed into a core−shell Cu 2−x S@ Ag 2 S structure via surface Pt doping. When the surface strain was relieved by a reduced Pt concentration at the nanoparticle surface, the core−shell transitioned back into a Janus structure. We expect that the facile composition fluctuations in multiphasic nanostructures will expand synthetic methodologies for the design and synthesis of intricate nanostructures with useful physicochemical properties.

Metal Cation Valency Dependence in Morphology Evolution of Cu2−xS Nanodisk Seeds and Their Pseudomorphic Cation Exchanges

“…A close‐up of the XRD pattern from 35–55° clearly shows that the pattern of Cu 2− x S component matches well with the roxbyite Cu 1.8 S, suggesting a crystal phase transformation from djurleite Cu 1.94 S to roxbyite Cu 1.8 S (Figure 5 h). These two Cu 2− x S phases have very similar crystal structures and can be facilely interconverted [72] . As a consequence, the crystal phase of Cu 2− x S in the heterostructure is assigned to roxbyite Cu 1.8 S, which can minimize the strain energy at the interface between the Cu 2− x S and the ZnS phase because they share a similar sulfur sublattice [26] .…”

Copper sulfide as the cation exchange template for synthesis of bimetallic catalysts for CO2electroreduction

“…For nanosheet samples, the hexanes dispersion containing Cnano-0 was added to an OAM solution (7 mL) containing the Ag precursor AgNO 3 . 29 The solution was rst degassed and heated to 50 C in N 2 and kept for another 30 min to complete the cation exchange reaction. The nanosheets were then washed with ethanol and hexanes and dispersed in hexanes for storage.…”

“…Cu sulde nanosheets (C-nano-0) C-nano-0 was synthesized with a modied colloidal synthesis recipe (Scheme 1a, see also Table 1 for sample nomenclature). 29,30 Typically, 257 mg copper(I) thiocyanate (CuSCN) was dispersed in 25 mL oleylamine (OAM). The mixture was rst degassed and heated in N 2 to 240 C for 30 min.…”

Copper Sulfide as the Cation Exchange Template for Synthesis of Bimetallic Catalysts for CO2 Electroreduction

“…For nanosheet samples, the hexanes dispersion containing C-nano-0 was added to an OAM solution (7 mL) containing the Ag precursor AgNO 3 . 29 The solution was first degassed and heated to 50°C in N 2 and kept for another 30 min to complete the cation exchange reaction. The nanosheets were then washed with ethanol and hexanes and dispersed in hexanes for storage.…”

“…C-nano-0 was synthesized with a modified colloidal synthesis recipe (Scheme 1a, see also Table 1 for sample nomenclature). 29,30 Typically, 257 mg copper (I) thiocyanate (CuSCN) was dispersed in 25 mL oleylamine (OAM). The mixture was first degassed and heated in N 2 to 240°C for 30 min.…”