Electronic Structure‐Dependent Water‐Dissociation Pathways of Ruthenium‐Based Catalysts in Alkaline H₂‐Evolution

Abstract

current conditions of electrocatalytic water splitting mainly include acidic and basic media. [5][6][7][8] When considering the huge difficulty in producing affordable acidic oxygen evolution electrodes in water splitting, the electrocatalytic water splitting in alkaline environments has become a meaningful strategy to produce H 2 on a large scale, [9][10][11][12][13] while the commercial alkaline hydrogen evolution reaction (HER) catalyst still relies on the metallic platinum (Pt), which confronts with slow water-dissociation kinetics, poor durability, and high costs. [5,[14][15][16] Highly active and cost-effective HER electrocatalysts are urgently needed for practical water splitting in alkaline conditions, especially alkaline seawater splitting. [17][18][19][20] Among the various transition metal-based hydrogenevolving materials, [21,22] recent studies have disclosed that Ru-based materials can serve as promising alkaline HER electrocatalysts due to their platinum-like electronic structures and relatively low cost (≈1/3 the price of Pt). [23][24][25] Regarding the pursuit of ultrahigh atomic efficiency of Ru metals, substantial efforts have been devoted to synthesizing single-atom Ru catalysts. [26,27] Although single-atom catalytic sites can facilely control the Ru coordination microenvironments and, in principle, obtain 100% atom utilization, these cationic states of single-atom Ru centers can hardly satisfy the alkaline HER electrocatalysis. [28] To increase Ruthenium (Ru)-based catalysts have displayed compelling hydrogen evolution activities, which hold the promising potential to substitute platinum in alkaline H 2 -evolution. In the challenging alkaline electrolytes, the water-dissociation process involves multistep reactions, while the profound origin and intrinsic factors of diverse Ru species on water-dissociation pathways and reaction principles remain ambiguous. Here the fundamental origin of water-dissociation pathways of Ru-based catalysts in alkaline media to be from their unique electronic structures in complex coordination environments are disclosed. These theoretical results validate that the modulated electronic structures with delocalization-localization coexistence at their boundaries between the Ru nanocluster and single-atom site have a profound influence on water-dissociation pathways, which push H 2 O* migration and binding orientation during the splitting process, thus enhancing the dissociation kinetics. By creating Ru catalysts with well-defined nanocluster, single-atom site, and also complex site, the electrocatalytic data shows that both the nanocluster and single-atom play essential roles in water-dissociation, while the complex site possesses synergistically enhanced roles in alkaline electrolytes. This study discloses a new electronic structure-dependent water-dissociation pathway and reaction principle in Ru-based catalysts, thus offering new inspiration to design efficient and durable catalysts for the practical production of H 2 in alkaline electrolytes.

“One Stone Five Birds” Plasma Activation Strategy Synergistic with Ru Single Atoms Doping Boosting the Hydrogen Evolution Performance of Metal Hydroxide

“…It has been reported that SCN − of potassium thiocyanate (KSCN) adsorb on the surface of both Ru nanocluster and Ru SAs while ethylene diamine tetra acetic acid (EDTA) mainly forms coordination bonds with Ru SAs. [31,32] With the addition of EDTA (10 mm) or KSCN (10 mm), the current density of β-Ni(OH) 2 /Ni-Ru SAs NSAs decreases more significantly in EDTA, due to the suppression of Ru SA sites by EDTA, thus demonstrating the important role of Ru SAs in the catalytic HER process. As the concentration of Ru clusters in β-Ni(OH) 2 /Ni-Ru SAs NSAs is only ≈10%, we think that the main active sites for HER are Ru SAs.…”

Enhanced Electron Confinement of p-Block Indium Site in Extended Macrocyclic Conjugation Boosting Oxygen Reduction to Hydrogen Peroxide

“…It is known that SCN − ions and EDTA could strongly bind to metal−N sites, which would block that metal site for O 2 adsorption, resulting in attenuated O 2 reduction activity. 44,55,56 As displayed in Figures 3d and S17, a distinct declining ORR activity for both InPc and InPPc can be observed after addition of SCN − , which can be ascribed to the blocking of the In−N active site by SCN − . 7,44,57 As shown in Figure S18, when EDTA was added, the performance of the catalyst became worse and the selectivity of H 2 O 2 decreased sharply.…”

“…The semicircular shape of the electrochemical impedance spectroscopy results (Figure S16) showed that the InPPc had a smaller charge transfer resistance compared to InPc at different overpotentials, suggesting the faster charge transfer rate in the 2e – ORR process. ,, To unveil the active sites of InPc and InPPc for 2e – ORR, poisoning experiments were also conducted in 0.1 M KOH electrolyte with or without addition of potassium thiocyanate (KSCN) and ethylene diamine tetraacetic acid (EDTA). It is known that SCN – ions and EDTA could strongly bind to metal–N sites, which would block that metal site for O 2 adsorption, resulting in attenuated O 2 reduction activity. ,, As displayed in Figures d and S17, a distinct declining ORR activity for both InPc and InPPc can be observed after addition of SCN – , which can be ascribed to the blocking of the In–N active site by SCN – . ,, As shown in Figure S18, when EDTA was added, the performance of the catalyst became worse and the selectivity of H 2 O 2 decreased sharply. These results verify that the In–N sites are mainly responsible for the 2e – ORR activity.…”

Review of Emerging Atomically Precise Composite Site‐Based Electrocatalysts

“…Yang et al utilized DFT calculations and experimental operations to systematically reveal the unique delocalization-localization coexistence at the interface of Ru nanoclusters and Ru single-atom. [80] By analyzing the adsorption and desorption behavior of different intermediates during HER, the authors discovered that the delocalized electrons in Ru nanoclusters delivered a stronger ability to adsorb OH*, and the localized electrons in single atom Ru were more inclined to adsorb H*. As depicted in Figure 10a, the active centers delivered Reproduced with permission.…”