Yolk-shell hierarchical catalyst with tremella-like molybdenum sulfide on transition metal (Co, Ni and Fe) sulfide for electrochemical water splitting.

Tremella-like MoS2 nano-sheets were directly synthesized on transition metal sulfides (TMS) via a solvothermal method, displaying extreme activities towards hydrogen and oxygen evolution in alkaline condition. The enhanced performance is attributed to the synergistic effect between the MoS2 shell and TMS yolk, expanded interlayer distance and the hierarchical structure.

Pt-Pd Bimetal Popcorn Nanocrystals: Enhancing the Catalytic Performance by Combination Effect of Stable Multipetals Nanostructure and Highly Accessible Active Sites.

Exploration of highly efficient electrocatalysts is significantly urgent for the extensive adoption of the fuel cells. Because of their high activity and super stability, Pt-Pd bimetal nanocrystals have been widely recognized as one class of promising electrocatalysts for oxygen reduction. This article presents the synthesis of popcorn-shaped Pt-Pd bimetal nanoparticles with a wide composition range through a facile hydrothermal strategy. The hollow-centered nanoparticles are surrounded by several petals and concave surfaces. By exploring the oxygen reduction reaction on the carbon supported Pt-Pd popcorns in perchloric acid solution, it is found that compared with the commercial Pt/C catalyst the present catalysts display superior catalytic performances in aspects of catalytic activity and stability. More importantly, the Pt-Pd popcorns display minor performance degradations through prolonged potential cycling. The enhanced performances can be mainly attributed to the unique popcorn structure of the Pt-Pd components, which allows the appearance and long existence of the high active sites with more accessibility. The present work highlights the key roles of accessible high active sites in the oxygen reduction reaction, which will ultimately guide the design of highly durable Pt-Pd catalysts.

High Durable Ternary Nanodendrites as Effective Catalysts for Oxygen Reduction Reaction.

Exploiting high catalytic activities and superior durability is significant for the lifetime and the cost of electro-catalysts for oxygen reduction reaction (ORR). Pt-Ni nanocrystals have attracted considerable attention owing to their exceptionally catalytic performance. However, the durability of Pt-Ni nanoparticles in acid media is still far below satisfaction. Consequently, improving the durability is extremely urgent for the application of Pt-Ni catalysts. To this end, we herein develop Pt-Ni-Ir ternary nanocrystals with dendritic shape, which are synthesized through a facile one-pot strategy. Such nanostructures featured with multibranches show an area specific activity of 1.58 mA cm(-2), seven times more than that of the commercial Pt/C catalyst (0.21 mA cm(-2)). More importantly, the dendritic Pt-Ni-Ir catalyst displays extraordinarily high durability. In contrast to the commercial Pt/C counterparts, which exhibit losses of 53.2% in EASA and 41% in area specific activity after 12 000 cycles of sweeping in the potential range of 0.6-1.1 V, only respective losses of 5.5% and 6% are detected for our dendritic Pt-Ni-Ir catalyst. The high activity and remarkable durability are mainly attributed to the dendritic morphology and the introduction of Ir. This work demonstrates that the Pt-Ni-Ir dendritic nanostructures are promising electro-catalysts for ORR.

Surface-Limited Synthesis of Pt Nanocluster Decorated Pd Hierarchical Structures with Enhanced Electrocatalytic Activity toward Oxygen Reduction Reaction.

Exploring superior catalysts with high catalytic activity and durability is of significant for the development of an electrochemical device involving the oxygen reduction reaction. This work describes the synthesis of Pt-on-Pd bimetallic heterogeneous nanostructures, and their high electrocatalytic activity toward the oxygen reduction reaction (ORR). Pt nanoclusters with a size of 1-2 nm were generated on Pd nanorods (NRs) through a modified Cu underpotential deposition (UPD) process free of potential control and a subsequent surface-limited redox reaction. The Pt nanocluster decorated Pd nanostructure with a ultralow Pt content of 1.5 wt % exhibited a mass activity of 105.3 mA mg(-1) (Pt-Pd) toward ORR, comparable to that of the commercial Pt/C catalyst but 4 times higher than that of carbon supported Pd NRs. More importantly, the carbon supported Pt-on-Pd catalyst displays relatively small losses of 16% in electrochemical surface area (ECSA) and 32% in mass activity after 10 000 potential sweeps, in contrast to respective losses of 46 and 64% for the commercial Pt/C catalyst counterpart. The results demonstrated that Pt decoration might be an efficient way to improve the electrocatalytic activity of Pd and in turn allow Pd to be a promising substitution for commercial Pt catalyst.