Continuous-flow hydrothermal synthesis for the production of inorganic nanomaterials

Abstract

As nanotechnology becomes increasingly important and ubiquitous, new and scalable synthetic approaches are needed to meet the growing demand for industrially viable routes to nanomaterial production. Continuous-flow hydrothermal synthesis or supercritical water hydrothermal synthesis (scWHS) is emerging as a versatile solution to this problem. The process was initially developed to take advantage of the tunable chemical and physical properties of superheated water to produce metal oxide nanoparticles by rapid nucleation and precipitation. The development of new mixing regimes and reactor designs has been facilitated by the modelling of reactor systems. These new reactor designs further exploit the properties of supercritical water to promote faster and more uniform mixing of reagent streams. The synthetic approach has been expanded beyond the metal oxide systems for which it was conceived, and now encompasses metal sulfides, metal phosphates, metal nanoparticles and metal-organic frameworks. In many of these cases, some degree of size and shape control can be achieved through careful consideration of both chemistry and reactor design. This review briefly considers the development of scWHS reactor technology, before highlighting some of our recent work in expanding the scope of this synthetic method to include a wide range of materials.

Microfluidic Synthesis Enables Dense and Uniform Loading of Surfactant‐Free PtSn Nanocrystals on Carbon Supports for Enhanced Ethanol Oxidation

“…[22][23][24][25][26][27] Such characteristics have encouraged researchers to explore the use of continuous flow-based microfluidic devices for synthesis of NPs with improved uniformity on al arge scale. [22][23][24][25][26][27] Such characteristics have encouraged researchers to explore the use of continuous flow-based microfluidic devices for synthesis of NPs with improved uniformity on al arge scale.…”

Microfluidic Generation of Nanomaterials for Biomedical Applications

“…In addition, NPs can be easily modified by adding new reagents at any demanded time point during the reaction procedures . The single‐phase continuous flow strategy is also highly scalable, and the throughput can be dramatically increased by integrating multiple identical microchannels parallelly on the same lamina . Hydrodynamic focusing (HF) techniques are also categorized as a specific type of continuous flow microfluidics.…”

Continuous Hydrothermal Flow Synthesis of Co1–xNixFe2O4 (x = 0–0.8) Nanoparticles and Their Catalytic Properties for CO Oxidation and Oxygen Evolution Reaction

“…Among all approaches available for synthesizing nanomaterials, continuous hydrothermal flow synthesis (CHFS), in a flow‐type apparatus (CHFS reactor) by using (near‐) supercritical water (scH 2 O, T ≥ 647 K, p ≥ 22.1 MPa) as the reaction medium is very attractive because of its relatively simple and scalable operation. It is usually realized by mixing a scH 2 O flow and a precursor flow in a mixer within a CHFS reactor, and the synthesized materials are collected as slurries at the reactor outlet.…”