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The preparation of ultra-small structurally ordered Pt-based intermetallic nanocrystals (< 3 nm) is still challenging due to the sintering during high temperature ordering. We report a strategy to construct size and distribution controllable Pt-based intermetallic nanocrystals based on ultra-thin metal oxide coating on Pt nanoparticles via atomic layer deposition. The area-selective and thickness controllable metal oxide coatings can not only provide metal atoms for alloying, but also prevent the sintering of Pt nanoparticles during subsequently fast ordering reduction. The prepared uniform PtZn intermetallic nanocrystals with the size of 2.50 ± 0.65 nm achieve outstanding single-cell performance with the mass activity of 0.48 A mg Pt −1 at 0.9 V and 10.42 % loss of mass activity after 30,000 voltage cycles, which is superior to commercial Pt/C. The enhanced activity and durability is attributed to the decreased binding energy of Pt-oxygen intermediates for weakly polarized surface Pt atoms and suppressed electrochemical Ostwald ripening. [Display omitted] • Uniform sub-3 nm PtZn intermetallic is synthesized by selectively coating ultra-thin ZnO on Pt nanoparticles via atomic layer deposition. • Ultra-thin ZnO coating can provide Zn atoms for alloying and prevent the sintering of nanoparticles during ordering reduction. • The enhanced activity is attributed to the decreased binding energy of Pt-oxygen intermediates for weakly polarized surface Pt atoms. • Sub-3 nm PtZn intermetallic nanocrystals with uniform size distribution suppress electrochemical Ostwald ripening in acid conditions. [ABSTRACT FROM AUTHOR]

The intrinsic carbon defects including pentagons, vacancies and sp3-hybridized carbon have recently been proposed as efficient reactive sites for oxygen reduction reaction (ORR). Nevertheless, it is still a great challenge to controllably introduce the intrinsic defects into carbon materials. Herein, a universal defect-engineering method via vaporized salt is reported to modify the N-doped carbon surface with abundant sp3-hybridized carbon defects. At an elevated temperature, the vaporized sodium chloride is found to selectively modulate the surface structure of carbon material. The obtained carbon-based electrocatalyst delivers an outstanding electrocatalytic ORR property with a half-wave potential (E 1/2) of 0.85 V vs. RHE and an excellent performance in zinc air battery (ZAB) test. The analysis of components and structures of surface elements via XANES and XPS reveals that the increasing sp3-hybridized carbon defects, induced by the vaporized-salt modification, are responsible for the enhancement of ORR performance. The theoretical calculations further suggest the sp3 component hybridizes with original sp2 carbon, forming efficient sp2/sp3 hybridized carbon sites towards ORR. Additionally, other halide salts are proved to have the similar effect on promoting ORR activity and this method can expand to other carbon-based materials, suggesting its universality and significance in synthesis of defect-rich carbon-based materials. [Display omitted] • A universal defect-engineering method via vaporized salt halide was developed. • The vaporized-salt-treated catalysts exhibited a superior ORR activity. • XANES, XPS, Raman and DFT calculations were applied to reveal the active sites. • The raised ORR activity was induced by the increasing sp3 carbon defects. [ABSTRACT FROM AUTHOR]

To effectively solve the electrochemical degradation problem of commercial Pt/C catalyst in fuel cell, nitrogen doped titania oxynitride (N-TiO 2) decorated Pt low-coordinated sites on a commercial Pt/C catalyst is achieved by coupling single-cycle selective atomic layer deposition of TiO 2 and following nitriding process that exhibits outstanding durability enhancement without changing the size distribution and wasting the electrochemical active area of Pt. [Display omitted] • TiO 2 was selectively decorated on Pt nanoparticles by atomic layer deposition. • The nitridation of TiO 2 stabilized the defect sites on Pt nanoparticles. • N-doped TiO 2 kept the exposure of Pt nanoparticles active sites. • N-doped TiO 2 decorated Pt/C showed durability promotion in fuel cell. The electrochemical dissolution of platinum (Pt) based nanoparticles and the consequent Pt active sites losses and particle aggregation have become a critical stability issue for the commercial proton exchange membrane fuel cell. Herein, nitrogen doped titania (N-TiO 2) stabilized Pt low-coordinated sites on a commercial Pt/C catalyst is achieved by simply coupling selective atomic layer deposition of TiO 2 and following nitrogen doping process. Selectively deposited N-TiO 2 on Pt nanoparticles keeps the exposure of Pt sites on (111) facets and increases the reduction states of Pt, which results in 1.7 times improvement of mass activity than commercial Pt/C. Besides, N-TiO 2 stabilized commercial Pt/C catalyst exhibits outstanding durability enhancement, showing only a 14.0% loss of mass activity after 30,000 potential cycles of rotating disk electrode tests and 91.7% retention after durability tests in humid fuel cell condition. The shielding role of N-TiO 2 could effectively inhibit the degradation of low-coordinated sites on Pt nanoparticles and maintain Pt size distribution, which is a promising strategy to prolong the lifetime of commercial Pt/C catalysts. [ABSTRACT FROM AUTHOR]

• A molten-salt-assisted thermal emitting method was developed to prepare Fe SACs. • The molten salt boosted the evaporation and transfer of Fe species from bulk Fe 2 O 3. • The gasified Fe species formed single-atom "Fe-N 4 -O 2 " sites on N-doped carbon. • The Fe-Z8NC&NaCl SACs exhibited a remarkable ORR activity in alkane media. • The method was valid for preparing other metal SACs (metal = Co, Mn, Cu and Ni). Efficient, durable and low-cost electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics are urgently needed for the energy conversion techniques, such as metal-air batteries and fuel cells. In this work, we develop a molten-salt-assisted thermal emitting approach to transform the cheap and easily obtainable bulk ferric (III) oxide powder into a highly efficient Fe single atom catalyst for cathodic oxygen reduction reaction. Benefiting from the strong polarity force of ionized cations and anions, the molten salt effectively facilitates breakage of chemical bonding in bulk Fe 2 O 3 and volatilization of Fe species far below the melting point of Fe 2 O 3 (1841 K), lowering the consumption of energy and time needed in the synthetic procedure. The vaporized Fe species are subsequently anchored onto the surface of nitrogen-doped porous carbon, evolving the single-atom "Fe-N 4 -O 2 " site catalyst. The obtained catalyst presents an excellent oxygen reduction reaction performance with half-wave potential of 0.896 V vs RHE in alkaline media, comparable to the most efficient non-precious metal catalysts and outperforming the benchmark system Pt/C. Furthermore, this method is demonstrated to be valid for synthesis of non-noble-metal single atom catalysts (metal = Co, Mn, Cu, Ni) by changing different metal oxides precursors. [ABSTRACT FROM AUTHOR]