Iced photochemical reduction to synthesize atomically dispersed metals by suppressing nanocrystal growth

Abstract

Photochemical solution-phase reactions have been widely applied for the syntheses of nanocrystals. In particular, tuning of the nucleation and growth of solids has been a major area of focus. Here we demonstrate a facile approach to generate atomically dispersed platinum via photochemical reduction of frozen chloroplatinic acid solution using ultraviolet light. Using this iced-photochemical reduction, the aggregation of atoms is prevented, and single atoms are successfully stabilized. The platinum atoms are deposited on various substrates, including mesoporous carbon, graphene, carbon nanotubes, titanium dioxide nanoparticles, and zinc oxide nanowires. The atomically dispersed platinum on mesoporous carbon exhibits efficient catalytic activity for the electrochemical hydrogen evolution reaction, with an overpotential of only 65 mV at a current density of 100 mA cm −2 and long-time durability (>10 h), superior to state-of-the-art platinum/carbon. This iced-photochemical reduction may be extended to other single atoms, for example gold and silver, as demonstrated in this study.

Engineering Local Coordination Environments of Atomically Dispersed and Heteroatom‐Coordinated Single Metal Site Electrocatalysts for Clean Energy‐Conversion

“…Many types of defects or heteroatoms on carbon‐based substrates such as single vacancy (SV) defects, double vacancy (DV) defects, edge, pyridine‐type N, pyrrole‐type N, and thiophene‐type S have been reported as effective coordination sites to stabilize various single atoms. For example, theoretical calculations revealed that Pt single atoms anchored on vacancies and edges of graphene supports are more stable than the corresponding Pt dimers and inhibit the formation of Pt clusters during the water activation process . At elevated temperatures, above 900 °C, the noble metal nanoparticles (Pd, Pt, Au) transform into thermally stable single atoms coordinated by four N atoms (MN 4 ) with a formation energy of −3.96 eV …”

“…The final samples exhibited high electrocatalytic performance without requiring any post treatment. In order to prevent uncontrolled nucleation and growth of metal particles at room temperature, a low temperature synthesis was also developed . Initially, a cobalt precursor underwent liquid‐phase reduction with hydrazine hydrate at −60 °C to form an atomically dispersed Co species .…”

Densely Populated Single Atom Catalysts

“…b) Schematic illustration of the ice‐photochemical process of H 2 PtCl 6 solution. Reproduced with permission . Copyright 2017, Nature Publishing Group.…”

“…This is the highest single Pt atom loading, which has never been reported before. Importantly, Wei et al prepared an atomically dispersed Pt suspension by using ultraviolet light to photochemically reduce the frozen chloroplatinic acid solution. The controlled reaction kinetics and thermodynamics have also been invented to prepare single atoms dispersed suspension by adding the frozen precursor solution into a reducing solution, or by directly reducing the metal precursor under a very low temperature of −60 °C .…”

Single‐Atom Catalysts in Catalytic Biomedicine

“…d) Schematic illustration of single Pt atoms on porous carbon. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/) . Copyright 2017, The Authors, published by Springer Nature.…”