Rare‐Earth Single‐Atom Catalysts: A New Frontier in Photo/Electrocatalysis

Abstract

through three steps: 1) at the catalyst surface, the reactants diffuse toward the active sites; 2) the reactants are adsorbed at the active sites and transformed into products via consecutive elementary reaction steps; 3) the products diffuse from the surface via chemical desorption. [4][5][6] To facilitate this transformational process, the catalytically active surface should contain many highly catalytically active sites. [7][8][9][10] However, in conventional bulk catalysts, typically, only a few surface atoms provide catalytic activity, and most of the subsurface atoms cannot directly participate in the reactions, thus resulting in atomic waste. [11][12][13][14][15] Recently, more efficient catalysts have been prepared by changing the active sites from those of a bulk catalyst to isolated atoms; these systems are known as single-atom catalysts (SACs). Thus, the term SAC is given to materials whose catalytically active sites are single atoms. The first discussion of SACs can be traced back to 2011, Zhang et al. reported Pt atoms anchored on FeO x (Pt 1 /FeO x ) for CO oxidation. [16] Crucially, when the size of catalysts reaches the atomic scale, distinctive properties that affect their chemical activities, conversion efficiencies, and stabilities emerge. In particular, unlike bulk catalysts, SACs maximize the use of the catalytically active metal atoms (nearly 100% atom efficiency). [17][18][19][20] Further, compared with bulk catalysts, SACs have unique advantages: 1) an unsaturated coordination environment that affects the affinity of the catalyst for intermediate species; 2) distinctive quantum size effects that yield discrete energy levels and frontier molecular orbital (FMO) occupancies; 3) strong atom support interactions that facilitate surface charge redistribution; 4) appropriate polarity to restrain shuttle effects during catalytic processes; 5) breaking of the energy scaling relationship based on the Sabatier principle for enhanced catalytic activity; and 6) site-to-site interactions between single atoms that enhance the catalytic kinetics. [21][22][23][24][25][26][27][28] In recent years, the use of transition-metal-based SACs [29][30][31] and precious-metal-based SACs [32][33][34] has developed rapidly, especially in the field of energy catalysis. In particular, research has focused on Fe, [35][36][37] Co, [38,39] Ni, [40,41] Mn, [42] Pt, [43,44] Ir, [45][46][47] Pd. [48,49] Owing to the strong atom-support interactions, the coupling of the metal and ligand orbitals in the support can result in changes in the d-band center (ε d ) of the metal atoms, [50,51] and this spin-orbit coupling, which results in a range of electronic states, is key to the success of heterogeneous Single-atom catalysts (SACs) provide well-defined active sites with 100% atom utilization, and can be prepared using a wide range of support materials. Therefore, they are attracting global attention, especially in the fields of energy conversion and storage. To date, research has focused on transitionmetal and precious-metal-bas...

Single-Atom Yttrium Engineering Janus Electrode for Rechargeable Na–S Batteries

“…Reducing the decomposition barrier of Na 2 S can greatly promote the utilization of active materials and reduce the formation of dead Na 2 S, thus achieving a long cycling life. − Therefore, we systematically calculated the decomposition energy barrier of Na 2 S on these stable substrates and NC. The results showed that YN 4 /C possessed the smallest decomposition barrier (1.52 eV) of Na 2 S in the charging process compared to MnN 4 /C (1.54 eV), ZnN 4 /C (1.84 eV), NiN 4 /C (1.93 eV), NC (2.00 eV), CuN 4 /C (2.02 eV), FeN 4 /C (1.87 eV), and CoN 4 /C (1.85 eV; Figures a and S1), demonstrating its great influence on the catalytic decomposition of Na 2 S, which was induced by the spin property of 4f electrons, further optimizing the density of states (DOS) . Notably, the above results showed that NC possessed almost the greatest decomposition barrier (2.00 eV) among the eight cases due to the absence of the catalytic MN 4 site.…”

“…In contrast, the interaction mechanism of single-atom sites toward Na–S battery systems has rarely been reported and remains ambiguous. Different from d-band levels of transition metals, rare-earth metals possess electron-rich 4f orbitals that result in very strong adsorption of reactant molecules and thus are thought to be catalytically inactive for room-temperature electrochemical reactions. , Excitedly, recent studies have confirmed that the spin–orbit interaction in rare-earth metals can be activated through engineering the single atomic species configuration, resulting in promising electrocatalytic activity. , As a result of the unique electronic property and large size of rare-earth atoms, rare-earth M–N x –C single-atom configurations frequently form stable high-coordination structures having more than four ligands . However, to the best of our knowledge, the rare-earth M–N 4 moiety with coordination unsaturated metal atoms exhibits high absorption electrocatalysis, which has not been explored yet in battery systems.…”

“…35,36 As a result of the unique electronic property and large size of rare-earth atoms, rare-earth M−N x −C single-atom configurations frequently form stable high-coordination structures having more than four ligands. 37 However, to the best of our knowledge, the rare-earth M−N 4 moiety with coordination unsaturated metal atoms exhibits high absorption electrocatalysis, 38 which has not been explored yet in battery systems. Given numerous degrees of freedom for adjusting the metal center and local atomic environments of single-atom catalysts, a conventional trial-and-error strategy significantly slows down the development of SACs in electrochemical energy storage and conversion.…”

Ethanol‐Induced Hydrogen Insertion in Ultrafine IrPdH Boosts pH‐Universal Hydrogen Evolution

“…[18] Alloy with light elements to form the interstitial Pd-H, [19,20] Pd-C, [21] Pd-O, [22,23] Pd-B, [24,25] Pd-P, [26,27] Pd-S [28] and Pd-N [29] compounds have been proved to be a powerful strategy to optimize the electrocatalytic performance. [30,31] The doping light elements can reform the performance of conventional Pd-based catalysts in the following ways [32] : i) The light elements (e.g., H, C, and B) can evenly infiltrate into the metal lattice in consequence of their smaller atomic size resulting in the lattice expansion of Pd; ii) There would occur a significant electron transfer between doping light atoms and adjacent Pd atoms on the basis of the different electronegativities; iii) The orbital hybrid mode in Pd-nonmetal alloys is s, p-d orbital hybridization between light elements and Pd atoms, distinct from the d-d orbital hybridization in conventional Pd-based catalysts, which can change the charge distribution of Pd atoms and ameliorate the adsorption free energy of catalytic sites. Among the Pd-nonmetal alloys, the Pd hydrides are the most widely investigated catalysts due to the extremely high affinity of Pd with H atoms.…”

Cyanogel‐Induced PdCu Alloy with Pd‐Enriched Surface for Formic Acid Oxidation and Oxygen Reduction

“…[1][2][3] Nevertheless, the major limitation to further commercialization of DFAFC remains the sluggish reaction kinetics of cathodic oxygen reduction reactions (ORR) and anodic formic acid oxidation reaction (FAOR). [4][5][6][7][8] Palladium (Pd), as an alternative material of Pt, has been widely used in ORR because of its comparable performance [9][10][11] Moreover, the direct dehydrogenation pathway is more profitable on Pd than on Pt in FAOR, which is manifested by faster reaction kinetics, lower oxidation potential, better anti-CO poisoning, and higher selectivity catalytic activity. [12][13][14] In spite of that, Pd has still suffered from difficulty in electrocatalytic property and soaring prices.…”