Over the last decade, significant effort has been devoted to the applications of hierarchically structured porous materials owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these materials is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into materials has led to a significant improvement in the performance of materials. Herein, recent progress in the applications of hierarchically structured porous materials from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically porous structures and properties, with examples of each type of hierarchically structured porous material according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically porous materials and to have a good idea about selecting and designing suitable hierarchically porous materials for a specific application. In addition to focusing on the applications of hierarchically porous materials, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically porous solids.

7337wileyonlinelibrary.com energy and the development of regenerative fuel cells and rechargeable metal-air batteries. [1][2][3][4] Note that overpotentials originating from the polarization phenomenon occurring at the electrodes induce a larger voltage window than the theoretical minimum one (1.23 V) to afford thermodynamic driving force. [ 5,6 ] As such, the sluggish apparent reaction kinetics necessitates the utilization of noble-metal-based electrocatalysts to achieve respectable performance, i.e., Pt for HER and IrO 2 / RuO 2 for OER, [ 7,8 ] though the scarcity and the consequent unfavorable cost prohibit the scale-up deployment in energy devices. Accordingly, great efforts have been made toward effi cient earth-enriched materials, such as OER catalysts working under strongly alkaline conditions and HER catalysts operating in strongly acidic mediums, due to the thermodynamic convenience and application prospect in alkaline electrolyzers or proton-exchange membrane. [9][10][11][12][13][14][15] On the one hand, pairing the OER and HER catalysts together in the same electrolyte is of practical values to accomplish overall water splitting, which remains diffi cult to achieve owing to the incompatibility of the stability and activity for the same catalyst systems in the operating pH regions, thereby leading to inferior effi ciency; on the other hand, the different catalysts intended to separate HER and OER may need distinct synthetic strategies and instruments with lowthroughput preparation processes. [16][17][18][19][20] Therefore, it is still a grand challenge to exploit bifunctional electrocatalysts in terms of not only featuring high effi ciency toward both hydrogen and oxygen evolution reactions, but also simplifying the system and reducing the costs.Transition Co-based catalysts have been regarded as promising alternatives to noble metals to drive the half reactions, for instance, metal Co, [ 21 ] CoS, [ 22 ] and CoSe, [ 23 ] for HER and Co oxides/(oxy)hydroxides designed for OER. [ 24,25 ] Indeed, CoO xcarbon composites have been implemented to be bifunctional and effective electrocatalysts for overall water splitting in base, wherein the involvement of conductive carbonaceous hosts is to overcome the disadvantages of self-accumulation and insuffi cient electric conductivity as to oxides. [ 26,27 ] Nonetheless, the sophisticated preparation and instability of active phases in acid propose an obstacle to further optimize the technology and fi nd Water splitting for the production of hydrogen and oxygen is an appealing solution to advance many sustainable and renewable energy conversion and storage systems, while the key fact depends on the innovative exploration regarding the design of effi cient electrocatalysts. Reported herein is the growth of CoP mesoporous nanorod arrays on conductive Ni foam through an electrodeposition strategy. The resulting material of well-defi ned mesoporosity and a high specifi c surface area (148 m 2 g −1 ) can be directly employed as a bifunctional and fl exible working elect...

Well crystallized nanoscale tubular materials have been synthesized via the reaction of TiO2 crystals of either anatase or rutile phase and NaOH aqueous solution. The atomic structure of the synthesized tubular material is imaged by high-resolution transmission electron microscopy (HRTEM), and the composition of individual tubular structures is determined using selected area energy dispersive X-ray spectroscopy (EDX). Our results show that the tubular materials are well crystallized tubes with an average diameter of about 9 nm and little dispersion, and are composed of mainly titanium and oxygen. The atomic ratio of O/Ti is found, however, to vary from tube to tube. Detailed electron and x-ray diffraction studies show that the structure of our titanium oxide nanotubes do not agree with those made of TiO2 crystals with either anatase or rutile phase. HRTEM observations revealed that the titanium oxide nanotubes usually have multiple shells, in analogy with multiwalled carbon nanotubes, but the shell spacing is about 0.75 nm which is much larger than that of the carbon nanotube, and the atomic structures of different shells are well correlated.

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Ordered mesoporous carbon materials have recently aroused great research interest because of their widespread applications in many areas such as adsorbents, catalysts and supports, gas storage hosts, and electrode materials. The direct synthesis strategy from organic-organic self-assembly involving the combination of polymerizable precursors and block copolymer templates is expected to be more flexible in preparing mesoporous carbons, compared with the traditional nanocasting strategy of complicated and high-cost procedures using mesoporous silica materials as the hard template. In this review, we present the fundamentals and recent advances related to the field of ordered mesoporous carbon materials from the direct synthesis strategy of block copolymer soft-templating, with a focus on their controllable preparation, modification and potential applications. Under the guidance of their formation mechanism, the preparation of ordered mesoporous carbons are discussed in detail by consulting different experimental conditions, including synthetic pathways, precursors, catalysts and templates. Both the mesopore size and morphology control are introduced. The potential applications of pure mesoporous carbons, nonmetallic- and metallic-modified mesoporous carbons, and some interpenetrating carbon-based composites are demonstrated. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of the ordered mesoporous carbons (232 references).

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Graphitic carbon nitride (g-C3N4) has been deemed a promising heterogeneous metal-free catalyst for a wide range of applications, such as solar energy utilization toward water splitting, and its photocatalytic performance is reasonably adjustable through tailoring its texture and its electronic and optical properties. Here phosphorus-doped graphitic carbon nitride nanostructured flowers of in-plane mesopores are synthesized by a co-condensation method in the absence of any templates. The interesting structures, together with the phosphorus doping, can promote light trapping, mass transfer, and charge separation, enabling it to perform as a more impressive catalyst than its pristine carbon nitride counterpart for catalytic hydrogen evolution under visible light irradiation. The catalyst has low cost, is environmentally friendly, and represents a potential candidate in photoelectrochemistry.

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