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Simultaneous optimization on bulk photogenerated‐carrier separation and surface atomic arrangement of catalyst is crucial for reactivity of CO2 photo‐reduction. Rare studies capture the detail that, better than in‐plane regulation, interlayer‐spacing regulation may significantly influence the carrier transport of the bulk‐catalyst thereby affecting its CO2 photo‐reduction in g‐C3N4. Herein, through a single atom‐assisted thermal‐polymerization process, single‐atom In‐bonded N‐atom (Inδ+–N4) in the (002) crystal planes of g‐C3N4 is originally constructed. This Inδ+–N4 reduces the (002) interplanar spacing of g‐C3N4 by electrostatic adsorption, which significantly enhances the separation of bulk carriers and greatly promotes the reactivity of CO2 photoreduction. The CO2 photo‐conversion performance of this resulted single‐atom In modified g‐C3N4 is significantly superior to other single atom loaded carbon nitride catalysts. Moreover, the Inδ+–N4 enhances the CO2 adsorption on g‐C3N4, reduces the *COOH formation energy, and optimizes the reaction path. It achieves a remarkable 398.87 µmol g−1 h−1 yield rate, 0.21% apparent quantum efficiency, and nearly 100% selectivity for CO without any cocatalyst or sacrificial agent. Through d(002) modulation of carbon nitride by single In atom, this study provides a ground‐breaking insight for reactivity enhancement from a double‐gain view of bulk structural control and surface atomic arrangement for CO2‐reduction photocatalysts. [ABSTRACT FROM AUTHOR]

This Letter reports Pd-nanocluster catalysts and their formation in ligand-free Suzuki-Miyaura reactions with palladium-(II) nitrate as a precatalyst. The catalysts are water-soluble neutral Pd tetramer and trimer in their singlet electronic states, as identified by UV-vis absorption spectroscopy, and are formed by leaching of spherical Pd(0) nanoparticles with an average diameter of about 3 nm. The Pd(0) nanoparticles are produced by reducing palladium-(II) nitrate and characterized with transmission electron microscopy and Pd K-edge extended X-ray fine structure spectroscopy. The Pd-(II) reduction is induced by ethanol, enhanced by potassium hydroxide, and monitored with X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) have been applied in many fields due to their superior catalytic performance. Because of the unique properties of the single-atom-site, using the single atoms as catalysts to synthesize SACs is promising. In this work, we have successfully achieved Co1 SAC using Pt1 atoms as catalysts. More importantly, this synthesis strategy can be extended to achieve Fe and Ni SACs as well. X-ray absorption spectroscopy (XAS) results demonstrate that the achieved Fe, Co, and Ni SACs are in a M1-pyrrolic N4 (M= Fe, Co, and Ni) structure. Density functional theory (DFT) studies show that the Co(Cp)2 dissociation is enhanced by Pt1 atoms, thus leading to the formation of Co1 atoms instead of nanoparticles. These SACs are also evaluated under hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the nature of active sites under HER are unveiled by the operando XAS studies. These new findings extend the application fields of SACs to catalytic fabrication methodology, which is promising for the rational design of advanced SACs. Synthesizing single-atom catalysts through a general method presents a great challenge. Here the authors report that Fe, Co and Ni single-atom catalysts can be obtained using pre-located isolated Pt atoms as the catalyst and identify the role of Pt single atoms in the synthesis process. [ABSTRACT FROM AUTHOR]

Colloidal copper sulfides produced in reactions of aqueous copper and sulfide ions are important for many materials applications, environment and mineral processing. Here, Cu x S nanoparticles formed and aged at varying copper sulfate to sodium sulfide ratios were studied using in situ UV–vis–NIR spectroscopy, dynamic light scattering, X-ray absorption spectroscopy, ex situ TEM, X-ray photoelectron spectroscopy and Raman scattering, and DFT + U calculations. It was established that the ratio of aqueous Cu2+ to S2− ions of 1:2 is critical for the reaction, which yields disordered covellite-like 4–6 nm Cu 0.7 S nanoparticles comprised polysulfide species at this and higher sulfide concentrations; upon aging, the particles release sulfur and transform to chalcocite-like structure (Cu 2-x S, x < 1). Conversely, at the "excess" of copper ions, Cu 2-x S-type particles grew into 12–14 nm "covellitic" nanoparticles. The optical absorbance at 1100–1200 nm commonly attributed to localized surface plasmon resonance increased with time and was lowest for Cu2+/S2− = 1:2. DFT + U calculations found that polysulfide stabilizes copper-deficit covellite, while Cu vacancies in chalcocite are more favorable and destabilized by S–S bonding; the Fermi level energy increases and the hole density decreases with polysulfide formation. We believe that CuS 2 clusters form initially, and following conversion of disulfide to polysulfide and then monosulfide ions rather than release of Cu determines the character of Cu x S nanoparticles. Image 1 • Cu 0.7 S particles of 4–6 nm formed for S2− to Cu2+ ions ratio of 2 and higher. • Covellite-type Cu x S NPs released S at the expense of polysulfide upon aging. • Cu 2-x S-type NPs formed and evolved to 14 nm covellitic ones for "excess" of Cu2+ ions. • NIR absorption maxima at 1100–1200 nm arose and increased upon aging. • Polysulfide species stabilized Cu-depleted covellite and reduced the density of holes. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO 2 in acidic media offers the advantage of high carbon utilization, but achieving high selectivity to C 2+ products at a low overpotential remains a challenge. We identified the chemical instability of oxide-derived Cu catalysts as a reason that advances in neutral/alkaline electrolysis do not translate to acidic conditions. In acid, Cu ions leach from Cu oxides, leading to the deactivation of the C 2+ -active sites of Cu nanoparticles. This prompted us to design acid-stable Cu cluster precatalysts that are reduced in situ to active Cu nanoparticles in strong acid. Operando Raman and X-ray spectroscopy indicated that the bonding between the Cu cluster precatalyst ligand and in situ formed Cu nanoparticles preserves a high density of undercoordinated Cu sites, resulting in a C 2 H 4 Faradaic efficiency of 62% at a low overpotential. The result is a 1.4-fold increase in energy efficiency compared with previous acidic CO 2 -to-C 2+ electrocatalytic systems.

The demand for green hydrogen has raised concerns over the availability of iridium used in oxygen evolution reaction catalysts. We identify catalysts with the aid of a machine learning-aided computational pipeline trained on more than 36,000 mixed metal oxides. The pipeline accurately predicts Pourbaix decomposition energy ( G pbx ) from unrelaxed structures with a mean absolute error of 77 meV per atom, enabling us to screen 2070 new metallic oxides with respect to their prospective stability under acidic conditions. The search identifies Ru 0.6 Cr 0.2 Ti 0.2 O 2 as a candidate having the promise of increased durability: experimentally, we find that it provides an overpotential of 267 mV at 100 mA cm -2 and that it operates at this current density for over 200 h and exhibits a rate of overpotential increase of 25 μV h -1 . Surface density functional theory calculations reveal that Ti increases metal-oxygen covalency, a potential route to increased stability, while Cr lowers the energy barrier of the HOO* formation rate-determining step, increasing activity compared to RuO 2 and reducing overpotential by 40 mV at 100 mA cm -2 while maintaining stability. In situ X-ray absorption spectroscopy and ex situ ptychography-scanning transmission X-ray microscopy show the evolution of a metastable structure during the reaction, slowing Ru mass dissolution by 20× and suppressing lattice oxygen participation by >60% compared to RuO 2 .

Multiferroics have tremendous potential to revolutionize logic and memory devices through new functionalities and energy efficiencies. To reach their optimal capabilities will require better understanding and enhancement of the ferroic orders and couplings. Herein, we use ϵ-Fe 2 O 3 as a model system with a simplifying single magnetic ion. Using 15, 20, and 30 nm nanoparticles, we identify that a modified and size-dependent Fe-O hybridization changes the spin-orbit coupling and strengthens it via longer octahedra chains. Fe-O hybridization is modified through the incommensurate phase, with a unique two-step rearrangement of the electronic environment through this transition with attraction and then repulsion of electrons around tetrahedral Fe. Interestingly, size effects disappear in the high-temperature phase where the strongest Fe-O hybridization occurs. By manipulating this hybridization, we tune and control the multiferroic properties.

Driving metal-cluster-catalyzed high-temperature chemical reactions by sunlight holds promise for the development of negative-carbon-footprint industrial catalysis, which has yet often been hindered by the poor ability of metal clusters to harvest and utilize the full spectrum of solar energy. Here, we report the preparation of Mo 2 TiC 2 MXene-supported Ru clusters (Ru/Mo 2 TiC 2 ) with pronounced broadband sunlight absorption ability and high sintering resistance. Under illumination of focused sunlight, Ru/Mo 2 TiC 2 can catalyze the reverse water-gas shift (RWGS) reaction to produce carbon monoxide from the greenhouse gas carbon dioxide and renewable hydrogen with enhanced activity, selectivity, and stability compared to their nanoparticle counterparts. Notably, the CO production rate of MXene-supported Ru clusters reached 4.0 mol·g Ru -1 ·h -1 , which is among the best reported so far for photothermal RWGS catalysts. Detailed studies suggest that the production of methane is kinetically inhibited by the rapid desorption of CO from the surface of the Ru clusters.

We explore the selective electrocatalytic hydrogenation of lignin monomers to methoxylated chemicals, of particular interest, when powered by renewable electricity. Prior studies, while advancing the field rapidly, have so far lacked the needed selectivity: when hydrogenating lignin-derived methoxylated monomers to methoxylated cyclohexanes, the desired methoxy group (-OCH 3 ) has also been reduced. The ternary PtRhAu electrocatalysts developed herein selectively hydrogenate lignin monomers to methoxylated cyclohexanes-molecules with uses in pharmaceutics. Using X-ray absorption spectroscopy and in situ Raman spectroscopy, we find that Rh and Au modulate the electronic structure of Pt and that this modulating steers intermediate energetics on the electrocatalyst surface to facilitate the hydrogenation of lignin monomers and suppress C-OCH 3 bond cleavage. As a result, PtRhAu electrocatalysts achieve a record 58% faradaic efficiency (FE) toward 2-methoxycyclohexanol from the lignin monomer guaiacol at 200 mA cm -2 , representing a 1.9× advance in FE and a 4× increase in partial current density compared to the highest productivity prior reports. We demonstrate an integrated lignin biorefinery where wood-derived lignin monomers are selectively hydrogenated and funneled to methoxylated 2-methoxy-4-propylcyclohexanol using PtRhAu electrocatalysts. This work offers an opportunity for the sustainable electrocatalytic synthesis of methoxylated pharmaceuticals from renewable biomass.

Utilizing the molecular beam epitaxy technique, a nanoscale thin-film magnet of c -axis-oriented Sm 2 Co 17 and SmCo 5 phases is stabilized. While typically in the prototype Sm(Co, Fe, Cu, Zr) 7.5-8 pinning-type magnets, an ordered nanocomposite is formed by complex thermal treatments, here, a one-step approach to induce controlled phase separation in a binary Sm-Co system is shown. A detailed analysis of the extended X-ray absorption fine structure confirmed the coexistence of Sm 2 Co 17 and SmCo 5 phases with 65% Sm 2 Co 17 and 35% SmCo 5 . The SmCo 5 phase is stabilized directly on an Al 2 O 3 substrate up to a thickness of 4 nm followed by a matrix of Sm 2 Co 17 intermixed with SmCo 5 . This structural transition takes place through coherent atomic layers, as revealed by scanning transmission electron microscopy. Highly crystalline growth of well-aligned Sm 2 Co 17 and SmCo 5 phases with coherent interfaces result in strong exchange interaction, leading to enhanced magnetization and magnetic coupling. The arrangement of Sm 2 Co 17 and SmCo 5 phases at the nanoscale is reflected in the observed magnetocrystalline anisotropy and coercivity. As next-generation permanent magnets require designing of materials at an atomic level, this work enhances our understanding of self-assembling and functioning of nanophased magnets and contributes to establishing new concepts to engineer the microstructure for beyond state-of-the-art magnets.