Hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy, which involves the process of harvesting renewable energy to split water into hydrogen and oxygen and ...then further utilization of clean hydrogen fuel. The production of hydrogen by water electrolysis is an essential prerequisite of the hydrogen economy with zero carbon emission. Among various water electrolysis technologies, alkaline water splitting has been commercialized for more than 100 years, representing the most mature and economic technology. Here, the historic development of water electrolysis is overviewed, and several critical electrochemical parameters are discussed. After that, advanced nonprecious metal electrocatalysts that emerged recently for negotiating the alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are discussed, including transition metal oxides, (oxy)hydroxides, chalcogenides, phosphides, and nitrides for the OER, as well as transition metal alloys, chalcogenides, phosphides, and carbides for the HER. In this section, particular attention is paid to the catalyst synthesis, activity and stability challenges, performance improvement, and industry‐relevant developments. Some recent works about scaled‐up catalyst synthesis, novel electrode designs, and alkaline seawater electrolysis are also spotlighted. Finally, an outlook on future challenges and opportunities for alkaline water splitting is offered, and potential future directions are speculated.
The hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy, which involves the process of harvesting renewable energy to split water into hydrogen and oxygen and then further utilization of hydrogen fuel. Alkaline water splitting represents the most mature and economic technology for clean hydrogen production, making high potential for successful implementation of hydrogen economy.
It remains highly desired but a great challenge to achieve atomically dispersed metals in high loadings for efficient catalysis. Now porphyrinic metal–organic frameworks (MOFs) have been synthesized ...based on a novel mixed‐ligand strategy to afford high‐content (1.76 wt %) single‐atom (SA) iron‐implanted N‐doped porous carbon (FeSA‐N‐C) via pyrolysis. Thanks to the single‐atom Fe sites, hierarchical pores, oriented mesochannels and high conductivity, the optimized FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and state‐of‐the‐art Pt/C, in both alkaline and more challenging acidic media. More far‐reaching, this MOF‐based mixed‐ligand strategy opens a novel avenue to the precise fabrication of efficient single‐atom catalysts.
Iron islands: Based on a mixed‐ligand strategy, a porphyrinic MOF was pyrolyzed to afford high‐content single‐atom iron‐implanted N‐doped porous carbon (FeSA‐N‐C). Thanks to the FeSA sites, hierarchical pores, oriented mesochannels, and high conductivity, FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and Pt/C, in both alkaline and the more challenging acidic media.
A high efficiency and great tunability of bandwidth and absorption‐range electromagnetic wave absorber is proposed without precedent. A series of 2D carbon‐based nanocomposites with the loading of ...cerium oxide (CN‐Ce) and other types of rare earth oxides (CN‐REOs) can be successfully synthesized by a simple solvothermal‐sintering method. As‐synthesized 2D nanocomposites with local graphite‐like C3N4 structure and trace N‐doped are identified by transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray powder diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. The CN‐REOs and polyvinylidene fluoride composite absorbers with reflection loss values above −40 dB are obtained in C‐band, X‐band, and Ku‐band, respectively. The empirical rules on effective bandwidth and frequency range are discovered and summarized, which can be successfully realized by simply tuning the doping amount or type of REO. The mechanism is explained by enhanced attenuation and tunable impedance matching. In addition co‐filled samples by two types of CN‐REOs nanocomposites are prepared to support these findings and inspire the preparation of absorber with desirable frequency band in the range of 2–18 GHz.
In the system of composites of PVDF and trace n‐doped carbon nanocomposites loaded with rare earth oxide, a high‐performance electromagnetic wave‐absorbing composite with adjustable electromagnetic wave absorption frequency range and adjustable effective absorption width is obtained. Regular performance is found based on extensive experimental data and analysis of intrinsic performance. In addition, the empirical conclusions are well‐validated by co‐filled (CN‐Ce+CN‐Eu)/PVDF samples.
Bimetallic metal–organic frameworks are rationally synthesized as templates and employed for porous carbons with retained morphology, high graphitization degree, hierarchical porosity, high surface ...area, CoNx moiety and uniform N/Co dopant by pyrolysis. The optimized carbon with additional phosphorus dopant exhibits excellent electrocatalytic performance for the oxygen reduction reaction, which is much better than the benchmark Pt/C in alkaline media.
Photo/electrochemical splitting of water to hydrogen (H 2 ) fuel is a sustainable way of meeting our energy demands at no environmental cost, but significant challenges remain: for example, the ...sluggish anodic reaction imposes a considerable overpotential requirement. By contrast, urea electrolysis offers the prospect of energy-saving H 2 production together with urea-rich wastewater purification, whereas the lack of inexpensive and efficient urea oxidation reaction (UOR) catalysts places constraints on the development of this technique. Here we report a porous rod-like NiMoO 4 with high oxidation states of the metal elements enabling highly efficient UOR electrocatalysis, which can be readily produced through annealing solid NiMoO 4 · x H 2 O as a starting precursor in Ar. This precursor gives the derived Ni/NiO/MoO x nanocomposite when switching the shielding gas from Ar to H 2 /Ar, exhibiting platinum-like activity for the hydrogen evolution reaction (HER) in alkaline electrolytes. Assembling an electrolytic cell using our developed UOR and HER catalysts as the anode and cathode can provide a current density of 10 milliamperes per square centimeter at a cell voltage of mere 1.38 volts, as well as remarkable operational stability, representing the best yet reported noble-metal-free urea electrolyser. Our results demonstrate the potential of nickel–molybdenum-based materials as efficient electrode catalysts for urea electrolysers that promises cost-effective and energy-saving H 2 production.
The development of intrinsically stretchable electronics poses great challenges in synthesizing elastomeric conductors, semiconductors and dielectric materials. While a wide range of approaches, from ...special macrostructural engineering to molecular synthesis, have been employed to afford stretchable devices, this review surveys recent advancements in employing various morphological and nanostructural control methods to impart mechanical flexibility and/or to enhance electrical properties. The focus will be on (1) embedding percolation networks of one-dimensional conductive materials such as metallic nanowires and carbon nanotubes in an elastomer matrix to accommodate large external deformation without imposing a large strain along the one-dimensional materials, (2) design strategies to achieve intrinsically stretchable semiconductor materials that include direct blending of semiconductors with elastomers and synthesizing semiconductor polymers with appropriate side chains, backbones, cross-linking networks, and flexible blocks, and (3) employing interpenetrating polymer networks, bottlebrush structures and introducing inclusions in stretchable polymeric dielectric materials to improve electrical performance. Moreover, intrinsically stretchable electronic devices based on these materials, such as stretchable sensors, heaters, artificial muscles, optoelectronic devices, transistors and soft humanoid robots, will also be described. Limitations of these approaches and measures to overcome them will also be discussed.
The development of intrinsically stretchable electronics poses great challenges in synthesizing elastomeric conductors, semiconductors and dielectric materials.
The exploitation of photocatalysts that harvest solar spectrum as broad as possible remains a high‐priority target yet grand challenge. In this work, for the first time, metal–organic framework (MOF) ...composites are rationally fabricated to achieve broadband spectral response from UV to near‐infrared (NIR) region. In the core–shell structured upconversion nanoparticles (UCNPs)‐Pt@MOF/Au composites, the MOF is responsive to UV and a bit visible light, the plasmonic Au nanoparticles (NPs) accept visible light, whereas the UCNPs absorb NIR light to emit UV and visible light that are harvested by the MOF and Au once again. Moreover, the MOF not only facilitates the generation of “bare and clean” Au NPs on its surface and realizes the spatial separation for the Au and Pt NPs, but also provides necessary access for catalytic substrates/products to Pt active sites. As a result, the optimized composite exhibits excellent photocatalytic hydrogen production activity (280 µmol g−1 h−1) under simulated solar light, and the involved mechanism of photocatalytic H2 production under UV, visible, and NIR irradiation is elucidated. Reportedly, this is an extremely rare study on photocatalytic H2 production by light harvesting in all UV, visible, and NIR regions.
Novel broadband spectrum‐responsive metal–organic framework (MOF) composites, upconversion nanoparticles‐Pt@MOF/Au, are fabricated based on plasmonic and upconversion effects. Strikingly, the composites exhibit considerable photocatalytic hydrogen production activities under UV, visible, or even near‐infrared light irradiation, which represents the first work reporting hydrogen production photocatalysts with considerable activity toward all these three regions of light irradiation.
Emerging as a potent alternative to classical metal-based semiconductor quantum dots (Qdots), carbon dots (Cdots) possess the distinctive advantages of convenient synthesis, prominent ...biocompatibility, colorful photoluminescence, and low cost. After almost a decade of extensive studies since their discovery, Cdots have widely been applied in bioimaging, sensing, catalysis, optoelectronics, energy conversion, etc. In this review, we first highlight the synthetic methods for Cdots in a macroscale manner. Second, we briefly discuss the fundamental mechanisms underlying the photoluminescence (PL). Third, we focus on their applications in sensing and bioimaging (including imaging-guided therapy). Some thoughts on future developments of Cdots are demonstrated as concluding remarks.
Oil sorbents play a very important part in the remediation processes of oil spills. To enhance the oil‐sorption properties and simplify the oil‐recovery process, various advanced oil sorbents and ...oil‐collecting devices based on them have been proposed recently. Here, we firstly discuss the design considerations for the fabrication of oil sorbents and describe recently developed oil sorbents based on modification strategy. Then, recent advances regarding oil sorbents mainly based on carbon materials and swellable oleophilic polymers are also presented. Subsequently, some additional properties are emphasized, which are required by oil sorbents to cope with oil spills under extreme conditions or to facilitate the oil‐collection processes. Furthermore, some oil‐collection devices based on oil sorbents that have been developed recently are shown. Finally, an outlook and challenges for the next generation of oil‐spill‐remediation technology based on oil‐sorbents materials are given.
Hydrophobic and oleophilic sorbent materials are demonstrated as promising candidates for the cleanup of oil spills. An overview of the latest developments and advances in the fabrication of oil sorbents through modification strategy, carbon‐based oil sorbents, and polymer‐based oil sorbents, as well as some smart oil sorbents and oil‐collecting devices based on oil‐sorbent materials are presented.
The anode oxygen evolution reaction (OER) is known to largely limit the efficiency of electrolyzers owing to its sluggish kinetics. While crystalline metal oxides are promising as OER catalysts, ...their amorphous phases also show high activities. Efforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 g in one batch) is presented with homogeneous elemental distribution via a facile supersaturated co‐precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes a faster surface self‐reconstruction process during OER, forming a metal oxy(hydroxide) active layer with rich oxygen vacancies, leading to superior OER activity (280 mV overpotential at 10 mA cm−2 in 0.1 m KOH). This opens up the potential of fast, facile, and scale‐up production of amorphous metal oxides for high‐performance OER catalysts.
Amorphous NiFeMo oxide (up to 515 g one batch) with homogeneous elemental distribution was synthesized through a facile supersaturated co‐precipitation method. The amorphous NiFeMo oxide undergoes rapid surface self‐reconstruction during OER that forms a metal oxy(hydroxide) active layer with oxygen vacancies, enabling efficient OER catalysis.
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