Carbon‐Supported Single‐Atom Catalysts for Formic Acid Oxidation and Oxygen Reduction Reactions

Abstract

Pt-based alloys to accelerate the kinetic activity and improve the intermediates poisoning resistance. [2] Meanwhile, at the cathode side of DFAFCs and PEMFCs, oxygen is reduced into water through a four electron oxygen reduction reaction (ORR) route. Despite the high-cost and limited supply, costly Pt-based electrocatalysts remain the widely investigated materials for efficient ORR activity. Although the kinetics of FAOR and ORR have been enhanced by applying these modified platinum group metals (PGMs), [3] the higher cost and poorer-stability have significantly held back the commercialization of DFAFCs. Therefore, it is highly imperative to explore PGM-free electrocatalysts with high activity and robust stability for both FAOR and ORR.Recently, numerous efforts have been made to theoretically and experimentally employ single-atom catalysts (SACs) that were dispersed in different supports for promising catalysis with high selectivity and maximized metal usage. [4] The synthesis methods have been summarized to prepare SACs with diverse strategies, [5] including atomic layer deposition (ALD), [6] host-guest strategy, [1] wetness impregnation, [7] polymer derived pyrolysis, [8] and so on. Particularly, these isolated SACs have been identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy. These synthesized SACs with different metals have been utilized for various catalytic reactions: carbon monoxide (CO) oxidation, [9] organic catalysis, [10] water splitting, [11] hydrogen oxidation reaction, [12] CO 2 reduction, [13] ORR, [14] FAOR, [1] nitrogen reduction reaction (NRR), [15] and lithium-sulfur batteries. [16] Integrated with numerous merits, metal SACs have been considered as an ideal platform to bridge the gap between high-efficiency and low PGMs usage toward fuel cells applications. 1) The highly stable SACs are dominantly determined by the strong chemical bonding between single metal atoms and the substrates.2) The sufficient and uniform electronic and geometric structures make SACs highly specific selectivity in many chemical applications. 3) The high utilization of SACs could significantly minimize the cost of metals, especially for precious metals. 4) The accessibility to regulate the coordination of SACs could trigger intriguingly active properties for catalysis. Hence, the rational combination of single metal sites and supports couldThe commercialization of fuel cells, especially for direct formic acid fuel cells (DFAFCs) and proton-exchange membrane fuel cells (PEMFCs), is significantly restrained by the high cost, poor stability, and sluggish kinetics of platinum group metals (PGM) catalysts for both the anodic formic acid oxidation reaction (FAOR) and the cathodic oxygen reduction reaction (ORR). Currently, it has confronted with challenges, including exploring highly active, cost-effective, and stable catalysts to replace PGM for DFAFCs and PEMFCs. Recently, the increasing investigation has been focused ...

Amidoxime Group‐Anchored Single Cobalt Atoms for Anti‐Biofouling during Uranium Extraction from Seawater

“…[ 10 ] Because of their high oxidation activity, ROS are found to work as antimicrobial substances by destroying organic components, including proteins and DNA, of biological cells. [ 11 ] However, to date, there is rare reports on the application of single atoms in the production of ROS and antimicrobial activity of single atoms.…”

“…However, uranium resources on land are limited, and there is an urgent need to explore new supplies of uranium resources. [ 11 , 14 ] Seawater contains thousands of times more uranium resources than land reserves, and the extraction of uranium from seawater is considered the most promising approach to meet the growing demands of uranium. [ 15 ] Numerous adsorbents have been fabricated for extracting uranium from seawater, and many of them exhibit promising uranium extraction capacity in natural seawater under laboratory conditions.…”

“…[ 18 ] Without specific targets for antimicrobial activity, ROS are reported to kill biological entities by acting on the ubiquitous organic components of biological cells and thus have a high potential to harbor broad anti‐biofouling activity. [ 11b ]…”

Phosphorus-Doped Graphene Electrocatalysts for Oxygen Reduction Reaction

“…The conversion efficiency of converting chemical energy into electrical energy is many folds higher than that of conversion of chemical energy into thermal (e.g., combustion) or kinetic energies (e.g., modern IC engines). Accordingly, great attention has been given to the study of fuel cells and metal-air batteries as the next-generation energy conversion techniques because these devices can directly convert chemical energy into electric energy with nearly zero carbon footprint [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. In fuel cells and metal-air batteries, the electrochemical reactions, in particular, the oxygen reduction reaction (ORR) in the cathode, determine the performance [ 10 , 11 ].…”

Polyoxometalate-based materials: quasi-homogeneous single-atom catalysts with atomic-precision structures

“…The typical preparation of SACs involves anchoring metal ions on various supports, including metal oxides, MOFs, ZIFs, COFs, and other carbon-based materials. [14][15][16][17][18][19] Although the development of SACs has been fast-tracked, there are still challenges ahead. The characterization of single-atom sites is extremely difficult without the utilization of extended X-ray absorption ne structure (EXAFS) spectroscopy and spherical aberration electron microscopy with atomic resolution, and the actual coordination states of metal atoms cannot commonly be accurately described.…”