Tongtong Liu,Hengyu Guo,Yanan Chen,Zhengping Zhang,Feng Wang
Pyrochlore ruthenate (Y 2 Ru 2 O 7–δ ) is highlighted as a promising oxygen evolution reaction (OER) catalyst for water splitting in polymer electrolyte membrane electrolyzers. However, an efficient electronic modulation strategy for Y 2 Ru 2 O 7–δ is required to overcome its electrochemical inertness. Herein, a surface manipulation strategy involving implanting MoO x moieties on nano Y 2 Ru 2 O 7–δ (Mo–YRO) using wet chemical peroxone method is demonstrated. In contrast to electronic structure regulation by intramolecular charge transfer (i.e., substitutional strategies), the heterogeneous Mo−O−Ru micro-interfaces facilitate efficient intermolecular electron transfer from [RuO 6 ] to MoO x . This eliminates the bandgap by inducing Ru 4 d delocalization and band alignment rearrangement. The MoO x modifiers also alleviate distortion of [RuO 6 ] by shortening Ru−O bond and enlarging Ru−O−Ru bond angle. This electronic and geometric structure tailoring enhances the OER performance, showing a small overpotential of 240 mV at 10 mA cm −2 . Moreover, the electron-accepting MoO x moieties provide more electronegative surfaces, which serve as a protective “fence” to inhibit the dissolution of metal ions, thereby stabilizing the electrochemical activity. This study offers fresh insights into the design of new-based pyrochlore electrocatalysts, and also highlights the versatility of surface engineering as a way of optimizing electronic structure and catalytic performance of other related materials.
Qilu Yao,Meng He,Xiaoling Hong,Xiaoliang Zhang,Zhang-Hui Lu
Hydrogen has been considered as an important alternative energy source for both environmental and economic reasons. The development of highly efficient and selective catalysts for hydrogen evolution from chemical hydrogen storage materials (e.g. hydrous hydrazine, N2H4·H2O) has become one of the most active research areas. In this study, MoOx-doped NiPt nanoparticles (NPs) have been successfully prepared via a simple one-step co-reduction strategy at room temperature. The characterization results show that the surfactant/support-free NiPt–MoOx NPs with a mean particle size of 5.0 nm are well-dispersed and in a low-crystalline/amorphous state. It is found that the prepared NiPt–MoOx samples show much higher catalytic activity toward the decomposition of N2H4 as compared to that of NiPt without the introduction of MoOx. In addition, among all the NiPt–MoOx NPs, the optimized Ni0.6Pt0.4–MoOx nanocatalyst shows 100% H2 selectivity and the best catalytic performance for the decomposition of N2H4 under alkaline conditions at 323 K. The TOF value of Ni0.6Pt0.4–MoOx NPs is found to be 822 h−1, which is among the highest values ever report for the same reaction. The excellent catalytic activities could be attributed to the modified electronic structure and the small particle size of NiPt NPs induced by the MoOx dopant. Other MoOx-doped Ni-based (NiM, M = Rh, Ir, Au, Ag and Ru) bimetallic catalysts also showed excellent catalytic activity. The present highly efficient and selective catalyst system may encourage the practical application of N2H4·H2O as a potential chemical hydrogen storage material.
Red mud supported Ni (Ni/RM) catalysts have been explored to the hydrodeoxygenation (HDO) of palmitic acid, however, the decarbonylation (DCO)/decarboxylation (DCO 2 ) is dominant. Therefore, the modification the oxophilic nature of catalysts can significantly impact their path of HDO and selectivity to aim products. Herein, MoO x -decorated Ni-Mo/RM catalysts with a hierarchical flower-like micro/nanostructure were prepared and applied in the HDO of palmitic acid. The effect of MoO x addition was investigated to control the path of HDO, resulting in the changing of carbon number distribution of the product. Combined with several comprehensive structural characterizations and catalytic HDO test, it is shown that the surface defective MoO x species and FeO x species near the metallic sites could significantly facilitate the C-O bond weakening, generated more direct deoxygenation product (hexadecane). Whereas the excessive Mo loading leads to clear altering of surface chemistry (i.e., decrease of specific surface area, pore volume and Mo 0 species, increase of reduction temperature and CO 2 adsorption, uneven dispersion, and agglomeration of Ni species), resulting in the decrease of palmitic acid conversion. As the main oxide in RM, Fe 2 O 3 , Al 2 O 3 and SiO 2 were used as supports to load Ni-Mo bimetals respectively to explore the contribution of different components in RM to the distribution of hydrodeoxygenation products of palmitic acid.
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