Rational design and preparation of single‐atom catalysts provide a promising strategy to significantly improve the electrocatalytic activity for water splitting. In particular, single atoms anchored at cationic vacancies can enhance the stability of the catalysts and improve reaction kinetics. In this work, Pt single atoms are loaded at layered α‐Ni2/3Fe1/3(OH)2 by oxidizing Fe2+ with H2PtCl6, and specifically, Pt atoms are anchored at in situ generated iron cationic vacancies during the process, resulting in stabilized Pt single atoms in the surface of α‐Ni2/3Fe1/3(OH)2 with the maximum loading of ≈6.15 wt%. The Pt single atoms not only act as active sites for hydrogen evolution reaction but also regulate the electronic structure of NiFe hydroxides and activate Ni atoms adjacent to Pt for oxygen evolution reaction. Therefore, the water‐splitting electrolyzer assembled with such a bifunctional catalyst shows a smaller overpotential than that with RuO2 and 20 wt% Pt/C catalysts as the anode and cathode, respectively, and efficient solar‐to‐hydrogen conversion. The results demonstrate the practical application of single‐atom Pt catalysts with low cost, large loading, and facile preparation route.

Exploring efficient electrocatalysts through controllable defect engineering in materials with low-cost and earth-abundant elements is highly desired for overall water splitting. Herein, a hybrid electrocatalyst was accomplished by growing layered...

The sandwich-like 2H MoS2 and unilaminar graphitic nanocarbon hybrid was synthesized via graphitizing threonic acid intercalated MoS2 precursor obtained using hydrothermal process. An excellent electrocatalytic efficiency of hydrogen evolution reaction with a remarkably small overpotential of 195 mV and a Tafel slope of 47 mV/decade is easily accessible for our hybridized catalyst in 0.5 M H2SO4 aqueous solution, much superior to that of pure 2H MoS2 and threonic acid intercalating MoS2 nanomaterials. Moreover, the detailed electrochemical activity surface area and electrochemical impedance suggest that the face-to-face stacking of unilaminar 2H MoS2 and graphitic nanocarbon at an alternating sequence accelerates the mass transport and electron transfer and, thus, enhances the efficiency for electrocatalytic water splitting. This work paves a neoteric and straightforward pathway for the fabrication of superlattice MoS2 and unilaminar graphitic nanocarbon hybrid, further improving the electrocatalytic efficiency of 2H MoS2 nanosheets via a synergistic modulation strategy.

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The dynamic evolution of active Fe species and carbon species during CO prereduction was revealed for Fe–Zr catalysts with different (monoclinic and tetragonal) zirconia supports (m-ZrO2 and t-ZrO2) on CO2 hydrogenation to light olefins. As the Fe loading reached 15 wt %, the corresponding Fe–K/m-ZrO2 catalyst presented a remarkable CO2 conversion (38.8%) and a high selectivity to light olefins in the hydrocarbon (C–H) products (42.8%). Using in situ characterization techniques including in situ X-ray diffraction (XRD), Raman, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the dynamic evolution (reduction and carburization) of iron oxides and the generation of diverse carbon species during CO prereduction on different ZrO2 supports were probed. The detected intermediate FeO species in the Fe–K/m-ZrO2 catalyst indicates a mild and sufficient reduction of Fe2O3 on m-ZrO2, promoting the carburization leading to smaller and more active iron species (Fe3O4 and χ-Fe5C2). More oxygen vacancies (Ov) on the surface of m-ZrO2 and the electron-donating ability of iron elements boosted the charge transfer between Fe and the ZrO2 support, forming a more active Fe species. For the Fe–K/t-ZrO2 catalyst, the low selectivity of C x H y implied its weak capacity to produce light olefins through CO2 hydrogenation. By comparison, the m-ZrO2 support provided relatively more strong basic sites, reducing the physically deposited carbon species and coke generation. The formation of more χ-Fe5C2 species contributed to the high yield of light olefins in products. Tuning the physicochemical properties and base microenvironment of supports could be an effective means to boost the iron catalyst activity for CO2 hydrogenation to olefins.

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Transition metal oxides have drawn tremendous interest due to their unique physical and chemical properties. As one of the most promising electrochromic (EC) materials, tungsten trioxide (WO3) has attracted great...

Three-dimensional (3D) nanospheres with a hollow interior derived from self-sacrificing templates have triggered great enthusiasm due to their structure-related performance for splitting water into hydrogen. Herein, a nickel-organic compound constituted of elemental nickel and glycine was first synthesized through a solvothermal process in an ethyl alcohol solution. Then, novel 3D hierarchical nanocatalysts consisting of ultrathin N-doped graphitic-nanocarbon-coated nickel clusters with a hollow interior structure were facilely fabricated via calcining the prepared nickel-organic compound. Outstanding electrocatalytic activity with a small overpotential of 70 mV and a low Tafel slope of 119 mV dec–1 for the hydrogen evolution reaction process can be readily achieved in a 1 M KOH aqueous solution through a controllable synthesis method. The investigation on electrocatalytic activity certifies that the thickness of the graphitic nanocarbon shells has a great influence on water splitting efficiency for hydrogen; the thinner the graphitic nanocarbon shells, the more excellent the electrocatalytic efficiency. Additionally, the detailed electrochemically active surface area suggests that the 3D hollow structured hybridized electrocatalysts with defect-rich ultrathin graphitic nanocarbon shells could limit the aggregation of nickel clusters, and small electrochemical impedance accelerates the penetration of electrons, inducing a high efficiency for electrochemical water splitting. Therefore, thoughtful design using the self-sacrificing template method provides a promising strategy for the fabrication of other hybridized composites with hierarchical architectures consisting of nanoclusters and nanocarbon for more efficient water splitting.