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.

Carbon-Encapsulated Ru–Co3O4 Nanosheets as Electrocatalysts for Acidic Water Oxidation

“…So far, Ir-based materials are considered the most effective acidic OER electrocatalysts. However, the scarcity and high cost of Ir-based catalysts have severely restricted their widespread utilization. − In contrast, Ru-based catalysts are more affordable and have high activity compared to Ir-based catalysts, but they suffer from poor durability due to the generation of soluble high-valence Ru species (RuO 4 ) under high oxidation potentials and in acidic environments. − Therefore, it is very important to design effective approaches to improve the stability and activity of Ru-based catalysts in acidic media. − Recently, two major strategies have been employed to address cost and stability issues, such as reducing the Ru content and confining the Ru atoms in an acid-resistant oxide substrate, including WO 3 , Co 3 O 4 , MnO 2 , MoO 3 , Ta 2 O 5 , etc. − Meanwhile, efforts have also been made in other directions, such as alloying Ru with another element, constructing well-defined interfaces through heterostructures, and designing defects (vacancies) rationally. − The electronic interaction between active sites and acid-resistant metal oxide can inhibit the generation of dissolvable high-valence species and regulate the adsorption energy of intermediates on reactive sites, thereby enhancing the stability and activity. For example, Lee and co-workers achieved a high acid-stabile Ir–MoO 3 OER catalyst by creating electron-deficient surfaces .…”