Pt atomic clusters (Pt-ACs) display outstanding electrocatalytic performance because of their unique electronic structure with a large number of highly exposed surface atoms. However, the small size and large specific surface area intrinsically associated with ACs pose challenges in the synthesis and stabilization of Pt-ACs without agglomeration. Herein, we report a novel one-step carbon-defect-driven electroless deposition method to produce ultrasmall but well-defined and stable Pt-ACs supported by defective graphene (Pt-AC/DG) structures. A theoretical simulation clearly revealed that the defective regions with a lower work function and hence a higher reducing capacity compared to those of normal hexagonal sites triggered the reduction of Pt ions preferentially at the defect sites. Moreover, the strong binding energy between Pt and carbon defects effectively restricted the migration of spontaneously reduced Pt atoms to immobilize/stabilize the resultant Pt-ACs. Electrochemical analyses demonstrated the high performance of Pt-ACs in catalyzing the hydrogen evolution reaction, showing a greatly enhanced mass activity, a high Pt utilization efficiency, and excellent stability compared with commercial Pt/C catalysts. The integration of proton exchange membrane water electrolysis with Pt-AC/DG as a cathode exhibited an excellent hydrogen generation activity and extraordinary stability (during 200 h of electrolysis) with a greatly reduced Pt usage compared with commercial Pt/C catalysts.

Transition-metal and nitrogen-codoped carbon-based (TM-N/C) catalysts are promising candidates for catalyzing the oxygen reduction reaction (ORR). However, TM-N/C catalysts suffer from insufficient ORR activity, unclear active site structure, and poor durability, particularly in acidic solution. Herein, we report single Co atom and N codoped carbon nanofibers (Co–N/CNFs) catalyst with high durability and desirable ORR activity in both acidic and alkaline solutions. The half-wave potential of the ORR shows a negligible decrease after a 10 000-cycle accelerated durability test. The high ORR durability is originated from the structural stability of the atomically dispersed Co-based active site, as revealed by probing analysis and density functional theory calculations. A passive direct methanol fuel cell with the Co–N/CNFs cathode delivers a maximal power density of 16 mW cm–2 and a remarkable stability during a 200 h test, demonstrating the application potential of Co–N/CNFs. The breakthrough of the highly durable TM-N/C ORR catalyst could open an avenue for affordable and durable fuel cells.

This paper describes a cation exchange approach to the synthesis of metal chalcogenide core-shell particles with the same size but a number of different compositions. This method begins with the preparation of colloidal spheres of amorphous Se (a-Se), followed by their reaction with Ag atoms to form Se@Ag2Se spheres. These core-shell spheres are then converted into Se@MSe (M = Zn, Cd, and Pb) via cation exchange with Zn2+, Cd2+, and Pb2+. All the colloidal spheres prepared using this method are monodispersed in size and characterized by a spherical shape and a smooth surface. Starting from the same batch of Se@Ag2Se, the resultant Se@MSe samples were essentially the same in size. Furthermore, these core-shell colloidal spheres can be easily made superparamagnetic by incorporating Fe3O4 nanoparticles into the a-Se cores. This synthetic approach provides a simple and versatile route to magnetoactive core-shell spheres with the same size but a range of different compositions. This study also implies that it is feasible to further increase the diversity of cations that can be used in the cation exchange of a colloidal system to produce multifunctional core-shell spheres with a variety of properties.