Partial‐Single‐Atom, Partial‐Nanoparticle Composites Enhance Water Dissociation for Hydrogen Evolution

Abstract

The development of an efficient electrocatalyst toward the hydrogen evolution reaction (HER) is of significant importance in transforming renewable electricity to pure and clean hydrogen by water splitting. However, the construction of an active electrocatalyst with multiple sites that can promote the dissociation of water molecules still remains a great challenge. Herein, a partial‐single‐atom, partial‐nanoparticle composite consisting of nanosized ruthenium (Ru) nanoparticles (NPs) and individual Ru atoms as an energy‐efficient HER catalyst in alkaline medium is reported. The formation of this unique composite mainly results from the dispersion of Ru NPs to small‐size NPs and single atoms (SAs) on the Fe/N codoped carbon (Fe–N–C) substrate due to the thermodynamic stability. The optimal catalyst exhibits an outstanding HER activity with an ultralow overpotential (9 mV) at 10 mA cm−2 (η10), a high turnover frequency (8.9 H2 s−1 at 50 mV overpotential), and nearly 100% Faraday efficiency, outperforming the state‐of‐the‐art commercial Pt/C and other reported HER electrocatalysts in alkaline condition. Both experimental and theoretical calculations reveal that the coexistence of Ru NPs and SAs can improve the hydride coupling and water dissociation kinetics, thus synergistically enhancing alkaline hydrogen evolution performance.

Clusters Induced Electron Redistribution to Tune Oxygen Reduction Activity of Transition Metal Single‐Atom for Metal–Air Batteries

“…In contrast, Fe Fe‐ACSA@NC with the highest Bader charge (0.79) demonstrates the weakest OH* binding trend ( E OH* =−2.79 eV), facilitating the desorption of OH* to spare the active site for the following reaction. Besides, the Fe−N bond length is also found to be linearly related to the ORR half‐wave potential consistent with the previous report (Figure 4f) [48] …”

CO‐Tolerant PEMFC Anodes Enabled by Synergistic Catalysis between Iridium Single‐Atom Sites and Nanoparticles

“…We resorted to X-ray absorption fine structure spectroscopy (XAFS) to unveil the precise coordination structure and electronic state of Ir species.F ourier transform extended Xray absorption fine structure (FT-EXAFS) of obtained catalysts and contrast samples are shown in Figure 2a.Irfoil exhibits at ypical first shell Ir-Ir pair at 2.40 while IrO 2 exhibits atypical Ir-O pair at 1.57 .InIr/C-HM, in addition to the Ir À Ir bond corresponding to metallic Ir nanoparticles, ap eak at 1.78 corresponding to the Ir À C/O bond is also noticed, originating from the partial oxidation of Ir nanoparticles and the contact between Ir nanoparticles and carbon substrate.AsforIr SA -N-C,the single prominent peak assignable to Ir-N/O scattering path located at 1.57 as well as the absence of Ir-Ir scattering path further prove the atomic dispersion of the Ir species.Whenitcomes to Ir NP @Ir SA -N-C, however, two equivalent scattering peaks are detected at 1.65 and 2.42 ,a ttributable to the Ir-N/C/O and metallic Ir-Ir contributions,r espectively.T hese results are in accord with the observations from HAADF-STEM, and similar to those reported in literature with SACs and nanoparticles concurrently observed. [10] We then carried out quantitative least-squares EXAFS fitting analysis to obtain the local chelation parameters for Ir (Figure 2b,T able S2). Theb estfitting analysis of Ir SA -N-C indicates that the main peak at 1.57 is derived from Ir-N and Ir-O first-shell coordination, Thee lectronic structure and the valence states were further investigated by ac ombination of X-ray absorption near-edge structure (XANES) spectroscopy and X-ray photoelectron spectroscopy (XPS).…”

Supramolecular Modulation of Molecular Conformation of Metal Porphyrins toward Remarkably Enhanced Multipurpose Electrocatalysis and Ultrahigh‐Performance Zinc–Air Batteries

“…[4,5] Unfortunately, noble metal (Pt, Ru)-based catalysts are high cost and have limited supply, thus making them difficult to be used in largescale commercial applications. [6,7] Therefore, the development of noble metal-free electrocatalysts is a promising alternative for large-scale productions in the future. [8] Among them, molecular catalysts have received extensive attention due to their unequivocal molecular structures, steady active sites, the controllable architectures and sustainable feature.…”