Vulcan XC-72 carbon-supported Pt−Ni alloy nanoparticle catalysts with different Pt/Ni atomic composition were prepared via the carbonyl complex route and their structure was studied by X-ray diffraction spectroscopy at wide angles (WAXS) and Debye function analysis (DFA). The very good agreement between the WAXS pattern and DFA simulation revealed that all the as-prepared Pt−Ni alloy catalysts have a unique and highly disordered face-centered cubic structure (solid solution) and that the lattice parameter decreases with the increase of the Ni content in the alloys. Transmission electron microscopy (TEM) images indicated that the as-prepared Pt−Ni alloy nanoparticles were well dispersed on the surface of the carbon support with a narrow particle size distribution and that their mean particle size slightly decreased with the increase in Ni content. Energy-dispersive X-ray analysis (EDX) confirmed that the catalyst composition was nearly the same as that of the nominal value. Thus, a comparative study was made for the oxygen reduction reaction (ORR) using the thin-film rotating ring-disk electrode method to the behavior of Pt based catalysts on the same carbon support, having the same metal loading, the same disordered structure, and a similar particle size. As compared to the Pt/C catalyst, the bimetallic catalysts with different Pt/ Ni atomic ratios exhibited an enhancement factor of ca. 1.5 to 3 in the mass activity and of ca. 1.5 to 4 in the specific activity for the ORR and a lower production of hydrogen peroxide in pure perchloric acid solution. The maximum activity of the Pt-based catalysts was found with ca. 30 ∼ 40 at. % Ni content in the alloys, which could originate from the favorable Pt−Pt interatomic distance. The ring-current measurements on all the catalysts showed similar behavior for hydrogen peroxide production. The enhanced electrocatalytic activity of as-prepared Pt−Ni alloy catalysts for the ORR is attributed to the high dispersion of the alloy catalysts, to their disordered structure, and to the favorable Pt−Pt mean interatomic distance caused by alloying.

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.

Single-site catalysts feature high catalytic activity but their facile construction and durable utilization are highly challenging. Herein, we report a simple impregnation-adsorption method to construct platinum single-site catalysts by synergic micropore trapping and nitrogen anchoring on hierarchical nitrogen-doped carbon nanocages. The optimal catalyst exhibits a record-high electrocatalytic hydrogen evolution performance with low overpotential, high mass activity and long stability, much superior to the platinum-based catalysts to date. Theoretical simulations and experiments reveal that the micropores with edge-nitrogen-dopants favor the formation of isolated platinum atoms by the micropore trapping and nitrogen anchoring of [PtCl 6 ] 2- , followed by the spontaneous dechlorination. The platinum-nitrogen bonds are more stable than the platinum-carbon ones in the presence of adsorbed hydrogen atoms, leading to the superior hydrogen evolution stability of platinum single-atoms on nitrogen-doped carbon. This method has been successfully applied to construct the single-site catalysts of other precious metals such as palladium, gold and iridium.

In this work, LiFePO4 with hierarchical microstructures self-assembled by nanoplates has been successfully synthesized by using poly(vinyl pyrrolidone) (PVP) as the surfactant in a benzyl alcohol system. The resulting dumbbell-like LiFePO4 microstructures are hierarchically constructed with two-dimensional nanoplates with ∼300 nm length and ∼50 nm thicknesses, while these tiny plates are attached side by side in an ordered fashion. Both benzyl alcohol and LiI acting as reducing agents promote the formation of LiFePO4, and the presence of PVP plays an important role in the construction of the hierarchically self-assembled microstructures. A reasonable formation mechanism is proposed on the basis of the result of time-dependent experiments. In addition, the cell performance of the synthesized LiFePO4 is better than that of the commercial LiFePO4, which makes it a promising cathode material for advanced electrochemical devices such as lithium-ion batteries and supercapacitors.

Highly dispersed boron-doped palladium nanoparticles supported on carbon black (Pd-B/C) with high Pd loading (ca. 40 wt % Pd) are synthesized through an aqueous process using dimethylamine borane as the reducing agent. The as-prepared Pd-B/C catalyst shows extraordinary activity toward formic acid electrooxidation compared to that of a commercially available Pd/C catalyst and the one prepared by using NaBH 4 as the reductant. Subsequent thermal treatment further enhances the durability of the electro-oxidation current on Pd-B/C, enabling this new material to be a promising anode catalyst for direct formic acid fuel cells. The superior performance of our Pd-B/C catalyst may arise from uniformly dispersed nanoparticles within optimal size ranges, the increase in surface-active sites, and the electronic modification effect of boron species.

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