Manipulating the Microenvironment of Single Atoms by Switching Support Crystallinity for Industrial Hydrogen Evolution

Abstract

Modulating the microenvironment of single‐atom catalysts (SACs) is critical to optimizing catalytic activity. Herein, we innovatively propose a strategy to improve the local reaction environment of Ru single atoms by precisely switching the crystallinity of the support from high crystalline and low crystalline, which significantly improves the hydrogen evolution reaction (HER) activity. The Ru single‐atom catalyst anchored on low‐crystalline nickel hydroxide (Ru‐LC‐Ni(OH)2) reconstructs the distribution balance of the interfacial ions due to the activation effect of metal dangling bonds on the support. Single‐site Ru with a low oxidation state induces the aggregation of hydronium ions (H3O+), leading to the formation of a local acidic microenvironment in alkaline media, breaking the pH‐dependent HER activity. As a comparison, the Ru single‐atom catalyst anchored on high‐crystalline nickel hydroxide (Ru‐HC‐Ni(OH)2) exhibits a sluggish Volmer step and a conventional local reaction environment. As expected, Ru‐LC‐Ni(OH)2 requires low overpotentials of 9 and 136 mV at 10 and 1000 mA cm−2 in alkaline conditions and operates stably at 500 mA cm−2 for 500 h in an alkaline seawater anion exchange membrane (AEM) electrolyzer. This study provides a new perspective for constructing highly active single‐atom electrocatalysts.

Mesoporous Electrocatalysts with p–n Heterojunctions for Efficient Electroreduction of CO2 and N2 to Urea

“…Additionally, it is observed that the peak area ratio of Co 3+ /Co 2+ in CeO 2 /Co 3 O 4 (0.80) is lower than that of pristine Co 3 O 4 (0.32), indicating that more Co 2+ is produced after the formation of interfaces between CeO 2 and Co 3 O 4 , and that electrons are transferred from CeO 6 octahedrons to stronger electronegativity CoO 6 octahedrons. , The spontaneous electron transfer between CeO 2 and Co 3 O 4 can generate local nucleophilic/electrophilic regions, which not only enhance the chemical adsorption ability of reactant molecules but also promote their activation ability . Moreover, the decrease in the valence state of cobalt also indicates that, compared to highly crystalline Co 3 O 4 , the low crystalline Co 3 O 4 in CeO 2 /Co 3 O 4 not only has richer unsaturated cobalt sites, but also enhances the interaction between heterogeneous interfaces, which promotes charge transfer and forms a favorable local reaction environment. , In the XPS spectra of O 1s (Figure S4), the characteristic peaks corresponding to surface lattice oxygen (O latt ), the surface adsorbed oxygen (O ads ) on oxygen vacancies, and surface residual water molecules (O w ), or oxygen in carbonates have binding energies of 530, 531.2, and 534.1 eV, respectively . According to Yang’s reports, the sample’s oxygen vacancy content increases with the strength of the surface adsorbed oxygen peak .…”

“…11 Moreover, the decrease in the valence state of cobalt also indicates that, compared to highly crystalline Co 3 O 4 , the low crystalline Co 3 O 4 in CeO 2 /Co 3 O 4 not only has richer unsaturated cobalt sites, but also enhances the interaction between heterogeneous interfaces, which promotes charge transfer and forms a favorable local reaction environment. 47,48 In the XPS spectra of O 1s (Figure S4), the characteristic peaks corresponding to surface lattice oxygen (O latt ), the surface adsorbed oxygen (O ads ) on oxygen vacancies, and surface residual water molecules (O w ), or oxygen in carbonates have binding energies of 530, 531.2, and 534.1 eV, respectively. 44 According to Yang's reports, the sample's oxygen vacancy content increases with the strength of the surface adsorbed oxygen peak.…”

Linking atomic to mesoscopic scales in multilevel structural tailoring of single-atom catalysts for peroxide activation

“…15–17 In SACs, both the interior microenvironment and atomically dispersed sites facilitate the regulation of molecular diffusion, adsorption, and surface reactions, creating opportunities for co-catalytic interactions. 18,19 The intrinsic activity of SACs is directly related to the configuration of the first coordination-shell, which determines their unique electronic and geometric properties. 20,21 Microscopic pores and defects in SACs provide a confinement effect that stabilizes metal sites and prevents the spatial migration and agglomeration of metal atoms, 22,23 while the mesoscale structure features multiple cavities or regions that efficiently direct reactants to the active sites.…”