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The catalytic activity of MnO 2 nanosheets towards oxygen evolution depends highly on their interlayer environment. We present a systematic investigation on fine-tuning of the interlayer environment of MnO 2 nanosheets by intercalation through a facile cation exchange with inexpensive first-row transition metal cations, including Ni 2 + , Co 2 + , Cu 2 + , Zn 2 + , and Fe 3 + ions. Among them, the Ni-intercalated MnO 2 nanosheets show remarkably enhanced OER activity and long-term stability, compared to pristine MnO 2 nanosheets. The overpotential of 330 mV at a current density of 10 mA cm À 2 is observed for the Ni-intercalated MnO 2 nanosheets. The ehancement mechanism of OER is studied by comparing physiochemical properties, such as the oxidation state of Mn, the interlayer distance, the increase in the disorder/twisting of MnO 6 octahedra, and the interlayer cooperative binding of water molecules. The Ni intercalation, different from other metal cations, strengthens the MnÀ O bond perpendicularly to the layer chains to facilitate the interlayer catalysis possibly between two Mn sites, and thus promotes the efficiency of oxygen evolution.

The development of the highly active nanocatalysts for effective hydrogen (H 2 ) production is of great significance for its practical applications in fuel cells. Herein, we reported a facile and scaleup synthetic methodology to grow in situ the remarkably active nanocatalysts of ultrasmall Ru nanoclusters on nitrogen (N)enriched hierarchically macroporous-mesoporous carbon supports (Ru@hPCN). The resultant Ru@hPCN combines structural and chemical merits of well-dispersed 0.7-nm Ru nanoclusters, N-enriched functional surface and 3D hierarchically porous framework, all of which synergistically boost the catalytic performance toward the hydrolysis of ammonia-borane (AB). An unprecedented activity with a turnover frequency of 1850 min À1 was achieved for the Ru@hPCN, which was 6.0 folds over that of commercialized Ru/C catalyst. Mechanism studies showed that the remarkably enhanced activity can be ascribed to the easier dissociation of electropositive H d + from H 2 O and the breakage of the BÀN bonds as well as favorable mass transport in the Ru@hPCN during AB hydrolysis.[a] Dr. scanning X-ray microprobe (Thermo ESCALAB 250Xi) with Al Ka radiation. ICP-MS was recorded on NexION 350D.

A colloidal-amphiphile-templated growth is developed to synthesize mesoporous complex oxides with highly crystalline frameworks. Organosilane-containing colloidal templates can convert into thermally stable silica that prevents the overgrowth of crystalline grains and the collapse of the mesoporosity. Using ilmenite CoTiO 3 as an example, the high crystallinity and the extraordinary thermal stability of its mesoporosity are demonstrated at 800 °C for 48 h under air. This synthetic approach is general and applicable to a series of complex oxides that are not reported with mesoporosity and high crystallinity, such as NiTiO . Those novel materials make it possible to build up correlations between mesoscale porosity and surfacesensitive physicochemical properties, e.g., electromagnetic response. For mesoporous CoTiO 3 , there is a 3 K increase of its antiferromagnetic ordering temperature, compared with that of nonporous one. This finding provides a general guideline to design mesoporous complex oxides that allow exploring their unique properties different from bulk materials.complex oxides, in general, has associated kinetic barriers from the slow diffusion in solids. [15] When there are two metal cations involved in crystallization of complex oxides like ABO 3 , their nonuniform distribution can result in spontaneous phase separation to form simple oxides. [16] A delicate balance of their sol-gel rates and the precautious control of thermal annealing procedure is needed. On the other hand, ordering competition between the crystallization of oxides and the mesoscale porosity brings profound difficulties to synthesize complex oxides (e.g., perovskites and ilmenites) with mesoporous structures. Crystallization usually leads to the formation of large crystalline grains that will create strong interfacial energies between crystalline walls and pores (e.g., air or templates). For any templated growth of mesoporous oxides using hydrocarbon-based surfactants or block copolymers (BCPs) as soft templates, [17][18][19] mesoscale nanostructures collapse prior to the crystallization of oxides, [20][21][22] because these soft templates are not mechanically strong and thermally stable under elevated temperatures (i.e., >500 °C).Nanostructures show a profound impact on the magnetic properties of materials as well and a few theoretical models have been proposed to understand magnetic behavior of nanoscale particles. [23][24][25][26][27][28][29][30] The magnetic ordering temperature (Curie temperature or Néel temperature) in magnetic materials

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