Region-Controlled Framework Interface Mediated Anion Exchange Chemical Transformation to Designed Metal Phosphosulfide Heteronanostructures.

Postsynthetic chemical transformation provides a powerful platform for creating heteronanostructures (HNs) with well-defined materials and interfaces that generate synergy or enhancement. However, it remains a synthetic bottleneck for the precise construction of HNs with increased degrees of complexity and more elaborate functions in a predictable manner. Herein, we define a general transformative protocol for metal phosphosulfide HNs based on tunable hexagonal Cu1.81S frameworks with corner-, edge- and face-controlled growth of Co2P domains. The region-controlled Cu1.81S-Co2P framework interfaces can serve as "kinetic barriers" in mediating the direction and rate between P and S anion exchange reactions, thus leading to a family of morphology and phase designed Cu3P1-xSx-Co2P HNs with hollow (branched, dotted and crown), porous and core-shell architectures. This study reveals the internal transformation mechanism between metal sulfide and phosphide nanocrystals, and opens up a new way for the rational synthesis of metastable HNs that are otherwise inaccessible.

Mn-Incorporation-Induced Phase Transition in Bottom-Up Synthesized Colloidal Sub-1-nm Ni(OH)2 Nanosheets for Enhanced Oxygen Evolution Catalysis.

Sub-1-nm structures are attractive for diverse applications owing to their unique properties compared to those of conventional nanomaterials. Transition-metal hydroxides are promising catalysts for oxygen evolution reaction (OER), yet there remains difficulty in directly fabricating these materials within the sub-1-nm regime, and the realization of their composition and phase tuning is even more challenging. Here we define a binary-soft-template-mediated colloidal synthesis of phase-selective Ni(OH)2 ultrathin nanosheets (UNSs) with 0.9 nm thickness induced by Mn incorporation. The synergistic interplay between binary components of the soft template is crucial to their formation. The unsaturated coordination environment and favorable electronic structures of these UNSs, together with in situ phase transition and active site evolution confined by the ultrathin framework, enable efficient and robust OER electrocatalysis. They exhibit a low overpotential of 309 mV at 100 mA cm-2 as well as remarkable long-term stability, representing one of the most high-performance noble-metal-free catalysts.

Phase Transformation from Amorphous RuSx to Ru-RuS2 Hybrid Nanostructure for Efficient Water Splitting in Alkaline Media.

Ruthenium (Ru)-based materials, as a class of efficient hydrogen evolution reaction (HER) catalysts, play an important role in hydrogen generation by electrolysis of water in an alkaline solution for clean hydrogen energy. Hybrid nanostructure (HN) materials, which include two or more components with distinct functionality, show better performance than their individual materials, since HN materials can potentially integrate their advantages and overcome the weaknesses. However, it remains a challenge to construct Ru-based HN materials with desired crystal phases for enhanced HER performances. Herein, a series of new Ru-based HN materials (t-Ru-RuS2, S-Ru-RuS2, and T-Ru-RuS2) through phase engineering of nanomaterials (PEN) and chemical transformation are designed to achieve highly efficient HER properties. Owing to the plentiful formation of heterojunctions and amorphous/crystalline interfaces, the t-Ru-RuS2 HN delivers the most outstanding overpotential of 16 mV and owns a small Tafel slope of 29 mV dec-1 at a current density of 10 mA cm-2, which exceeds commercial Pt/C catalysts (34 mV, 38 mV dec-1). This work shows a new insight for HN and provides alternative opportunities in designing advanced electrocatalysts with low cost for HER in the hydrogen economy.

Selective-Epitaxial Hybrid of Tripartite Semiconducting Sulfides for Enhanced Solar-to-Hydrogen Conversion.

The design and synthesis of advanced semiconductors is crucial for the full utilization of solar energy. Herein, colloidal selective-epitaxial hybrid of tripartite semiconducting sulfides CuInS2 Cd(In)SMoS2 heteronanostructures (HNs) via lateral- and vertical-epitaxial growths, followed by cation exchange reactions, are reported. The lateral-epitaxial CuInS2 and Cd(In)S enable effective visible to near-infrared (NIR) solar spectrum absorption, and the vertical-epitaxial ultrathin MoS2 offer sufficient edge sulfur sites for the hydrogen evolution reaction (HER). Furthermore, the integrated structures exhibit unique epitaxial-staggered type II band alignments for continuous charge separation. They achieve the H2 evolution rate up to 8 mmol h-1 g-1 , which is ≈35 times higher than bare CdS and show no deactivation after long-term cycling, representing one of the most efficient and robust noble-metal-free photocatalysts. This design principle and transformation protocol open a new way for creating all-in-one multifunctional catalysts in a predictable manner.

Soft chemistry of metastable metal chalcogenide nanomaterials.

The metastable nature of metal chalcogenide nanomaterials (MCNs) provides us with fresh perspectives and plentiful grounds in the search of new strategies for physicochemical tuning. In the past decade, numerous efforts have been devoted to synthesizing and modifying diverse emerging MCNs based on their "soft chemistry", that is, gently regulating the composition, structure, phase, and interface while not entirely disrupting the original features. This tutorial review focuses on design principles based on the metastability of MCNs, such as ion mobility and vacancy, thermal and structural instability, chemical reactivity, and phase transition, together with corresponding soft chemical approaches, including ion-exchange, catalytic growth, segregation or coupling, template grafting or transformation, and crystal-phase engineering, and summarizes recent advances in their preparation and modification. Finally, prospects for the future development of soft chemistry-directed synthetic guidelines and metastable metal chalcogenide-derived nanomaterials are proposed and highlighted.

Regioselective Construction of Chemically Transformed Phosphide-Metal Nanoheterostructures for Enhanced Hydrogen Evolution Catalysis.

Engineering nanoheterostructures (NHs) plays a key role in exploring novel or enhanced physicochemical properties of nanocrystals. Despite previously reported synthetic methodologies, selective synthesis of NHs to achieve the anticipated composition and interface is still challenging. Herein, we presented a colloidal strategy for the regioselective construction of typical Ag-Co2P NHs with precisely controlled location of Ag nanoparticles (NPs) on unique chemically transformed Co2P nanorods (NRs) by simply changing the ratio of different surfactants. As a proof-of-concept study, the constructed heterointerface-dependent hydrogen evolution reaction (HER) catalysis was demonstrated. The multiple Ag NP-tipped Co2P NRs exhibited the best HER performance, due to their more exposed active sites and the synergistic effect at the interfaces. Our results open up new avenues in rational design and fabrication of NHs with delicate control over the spatial distribution and interfaces between different components.

Precursor Triggering Synthesis of Self-Coupled Sulfide Polymorphs with Enhanced Photoelectrochemical Properties.

Heteronanostructures have attracted intensive attention due to their electronic coupling effects between distinct components. Despite tremendous advances of nanostructure fabrication, combining independent polymorphs by forming heterojunction is still challenging but fascinating, such as copper sulfides (Cu2-xS), exhibiting varying band gaps and crystal structures with various stoichiometries. Herein, self-coupled Cu2-xS polymorphs (Cu1.94S-CuS) by a facile one-pot chemical transformation route have been reported for the first time. Unprecedentedly, a manganous precursor plays a crucial role in inducing and directing the formation of such a dumbbell-like architecture, which combines 1D Cu1.94S with 2D CuS. During the transformation, Mn2+ ions mediate the Cu+ ions diffusion and phase conversion process particularly. Furthermore, this self-coupled polymorphic structure exhibits significantly enhanced photoelectrochemical properties compared with the individual Cu1.94S nanocrystals and CuS nanoplates, originating from the unique heterointerfaces constructed by intrinsic band alignment and the enhanced contact between high conductivity hexagonal planes and the working electrode revealed by density functional theory (DFT) calculations. So we anticipate this emerging interfacial charge separation could provide useful hints for applications in optoelectronic devices or photocatalysis.

A trialkylphosphine-driven chemical transformation route to Ag- and Bi-based chalcogenides.

From the standpoint of chemistry, the metastable nature of nanocrystals provides us plentiful ground for the research of new nanoscale structural transformations. Herein, we report a new phenomenon that trialkylphosphine (TAP) can extract the Ag(+) and Bi(3+) from their nanostructural chalcogenides and reduce them to the zerovalent state. Based on this principle, a trialkylphosphine-driven chemical transformation route has been developed for the synthesis of a series of metals and metal-sulfide heterostructures with multiple sulfides as the precursors. Using this reaction principle, Ag, Bi, Ag-Ni3S2, Ag-ZnS, Ag-AgInS2, Ag-Bi, and Bi-Cu7S4 nanostructures can be successively synthesized. These Ag- or Bi-based metal chalcogenide heteronanostructures with interesting optical properties or multifunctionalities could be of special interest for a variety of applications, including high-performance catalysis, biological and biomedical sensing, photovoltaic devices, and a new generation of optoelectronic devices.

Colloidal synthesis of ternary AgFeS2 nanocrystals and their transformation to Ag2S-Fe7S8 heterodimers.

Ternary-/hetero-nanocrystals: a facile one-pot colloidal route for controlled synthesis of ternary AgFeS2 nanocrystals, which have a band gap of 1.21 eV, is presented for the first time. Such ternary AgFeS2 nanocrystals can transform to Ag2 S-Fe7 S8 heterodimers by internal thermal reaction at elevated temperature, providing a new route to synthesize semiconductor hetero-nanostructures.

One-pot controlled synthesis of hexagonal-prismatic Cu1.94S-ZnS, Cu1.94S-ZnS-Cu1.94S, and Cu1.94S-ZnS-Cu1.94S-ZnS-Cu1.94S heteronanostructures.

Playing six-a-side: Complex hexagonal prism Cu(1.94)S-ZnS heteronanostructures were synthesized by a colloidal route. Cu(1.94)S-ZnS, Cu(1.94)S-ZnS-Cu(1.94)S, and Cu(1.94)S-ZnS-Cu(1.94)S-ZnS-Cu(1.94)S structures are formed with screw-, dumbbell-, and sandwich-like shapes by using CuI and [Zn(S(2)CNEt(2))(2)] as precursors in oleylamine.