The “edge‐free” monolayer MoS2
films supported by 3D nanoporous gold show high catalytic activities towards hydrogen evolution reaction (HER), originating from large out‐of‐plane strains that are ...geometrically required to manage the 3D curvature of bicontinuous nanoporosity. The large lattice bending leads to local semiconductor‐to‐metal transition of 2H MoS2 and the formation of catalytically active sites for HER.
A two-dimensional crystal of molybdenum disulfide (MoS2) monolayer is a photoluminescent direct gap semiconductor in striking contrast to its bulk counterpart. Exfoliation of bulk MoS2 via Li ...intercalation is an attractive route to large-scale synthesis of monolayer crystals. However, this method results in loss of pristine semiconducting properties of MoS2 due to structural changes that occur during Li intercalation. Here, we report structural and electronic properties of chemically exfoliated MoS2. The metastable metallic phase that emerges from Li intercalation was found to dominate the properties of as-exfoliated material, but mild annealing leads to gradual restoration of the semiconducting phase. Above an annealing temperature of 300 °C, chemically exfoliated MoS2 exhibit prominent band gap photoluminescence, similar to mechanically exfoliated monolayers, indicating that their semiconducting properties are largely restored.
Chemical doping has been demonstrated to be an effective way to realize new functions of graphene as metal‐free catalyst in energy‐related electrochemical reactions. Although efficient catalysis for ...the oxygen reduction reaction (ORR) has been achieved with doped graphene, its performance in the hydrogen evolution reaction (HER) is rather poor. In this study we report that nitrogen and sulfur co‐doping leads to high catalytic activity of nanoporous graphene in HER at low operating potential, comparable to the best Pt‐free HER catalyst, 2D MoS2. The interplay between the chemical dopants and geometric lattice defects of the nanoporous graphene plays the fundamental role in the superior HER catalysis.
Together they're strong: Nitrogen and sulfur co‐doped nanoporous graphene displays high catalytic activity in the hydrogen evolution reaction (HER) at low operating potential. The interplay between the chemical dopants and geometric lattice defects is crucial for the superior HER performance by minimizing the Gibbs free energy of H* absorption.
Constructing bulk graphene materials with well‐reserved 2D properties is essential for device and engineering applications of atomically thick graphene. In this article, the recent progress in the ...fabrications and applications of sterically continuous porous graphene with designable microstructures, chemistries, and properties for energy storage and conversion are reviewed. Both template‐based and template‐free methods have been developed to synthesize the 3D continuously porous graphene, which typically has the microstructure reminiscent of pseudo‐periodic minimal surfaces. The 3D graphene can well preserve the properties of 2D graphene of being highly conductive, surface abundant, and mechanically robust, together with unique 2D electronic behaviors. Additionally, the bicontinuous porosity and large curvature offer new functionalities, such as rapid mass transport, ample open space, mechanical flexibility, and tunable electric/thermal conductivity. Particularly, the 3D curvature provides a new degree of freedom for tailoring the catalysis and transport properties of graphene. The 3D graphene with those extraordinary properties has shown great promises for a wide range of applications, especially for energy conversion and storage. This article overviews the recent advances made in addressing the challenges of developing 3D continuously porous graphene, the benefits and opportunities of the new materials for energy‐related applications, and the remaining challenges that warrant future study.
3D continuously porous graphene formed by folding a single‐sheet graphene into a 3D porous architecture has well‐retained 2D properties of graphene and novel functionalities from 3D structure, representing a distinct class of graphene materials with numerous unique and extraordinary properties. A comprehensive review of 3D continuously porous graphene and their applications in energy conversion and storage is provided.
Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage. Layered oxides, especially manganese-based oxides, are the most popular cathodes due to their high reversible ...capacity and use of earth-abundant elements. However, less noticed is the fact that the interface of layered cathodes always suffers from atmospheric and electrochemical corrosion, leading to severely diminished electrochemical properties. Herein, we demonstrate an environmentally stable interface via the superficial concentration of titanium, which not only overcomes the above limitations, but also presents unique surface chemical/electrochemical properties. The results show that the atomic-scale interface is composed of spinel-like titanium (III) oxides, enhancing the structural/electrochemical stability and electronic/ionic conductivity. Consequently, the interface-engineered electrode shows excellent cycling performance among all layered manganese-based cathodes, as well as high-energy density. Our findings highlight the significance of a stable interface and, moreover, open opportunities for the design of well-tailored cathode materials for sodium storage.The interface of layered cathodes for sodium ion batteries is subject to atmospheric and electrochemical corrosions. Here, the authors demonstrate an environmentally stable interface via titanium enriched surface reconstruction in a layered manganese-based oxide.
Owing to its earth abundance, low kinetic overpotential, and superior stability, NiFe‐layered double hydroxide (NiFe‐LDH) has emerged as a promising electrocatalyst for catalyzing water splitting, ...especially oxygen evolution reaction (OER), in alkaline solutions. Unfortunately, as a result of extremely sluggish water dissociation kinetics (Volmer step), hydrogen evolution reaction (HER) activity of the NiFe‐LDH is rather poor in alkaline environment. Here a novel strategy is demonstrated for substantially accelerating the hydrogen evolution kinetics of the NiFe‐LDH by partially substituting Fe atoms with Ru. In a 1 m KOH solution, the as‐synthesized Ru‐doped NiFe‐LDH nanosheets (NiFeRu‐LDH) exhibit excellent HER performance with an overpotential of 29 mV at 10 mA cm−2, which is much lower than those of noble metal Pt/C and reported electrocatalysts. Both experimental and theoretical results reveal that the introduction of Ru atoms into NiFe‐LDH can efficiently reduce energy barrier of the Volmer step, eventually accelerating its HER kinetics. Benefitting from its outstanding HER activity and remained excellent OER activity, the NiFeRu‐LDH steadily drives an alkaline electrolyzer with a current density of 10 mA cm−2 at a cell voltage of 1.52 V, which is much lower than the values for Pt/C–Ir/C couple and state‐of‐the‐art overall water‐splitting electrocatalysts.
The sluggish hydrogen evolution reaction (HER) kinetics on a NiFe layered double hydroxide (LDH) are substantially sped up in a novel approach by tailoring its water dissociation active sites in alkaline solutions. The resultant Ru‐doped NiFe‐LDH nanosheet exhibits a greatly enhanced HER activity in alkaline solution, which is superior to those of Pt/C and state‐of‐the‐art Pt‐free electrocatalysts.
Multifunctional nanoporous graphene is realized as a heat generator to convert solar illumination into high‐energy steam. The novel 3D nanoporous graphene demonstrates a highly energy‐effective steam ...generation with an energy conversation of 80%.
Metallic materials are key for electrochemical energy conversion and storage when they are tailored into electrodes designed for rapid reaction kinetics, high electrical conductivities, and high ...stability. Nanoporous metals formed by dealloying could meet all of these requirements, as the dealloyed products beckon energy researchers with their fascinating structures and outstanding performance. In this article, we discuss the characteristics of dealloyed materials related to their functions in energy devices. We then review nanoporous metal electrodes for applications in fuel cells, supercapacitors, and batteries to provide insights into selection and design criteria for meeting the diverse needs of energy conversion and storage.
Long-term exposure to ambient and household particulate matter (PM2.5) causes death and health loss, and both are the leading risk factor to global disease burden. We assessed spatiotemporal trends ...of ambient and household PM2.5 attributable burdens across various diseases at the global, regional, and national levels from 1990 to 2017.
Data on PM2.5-attributable disease burdens were extracted from the Global Burden of Disease (GBD) study 2017. Numbers and age-standardized rates (ASRs) of deaths, disability-adjusted life years (DALYs) and corresponding estimated annual percentage change (EAPC) were estimated by disease, age, sex, Socio-demographic Index (SDI), locations.
Exposure to PM2.5 contributed to 4.58 million deaths and 142.52 million DALYs globally in 2017, among which ambient PM2.5 contributed to 64.2% deaths and 58.3% DALYs. ASRs of deaths and DALYs in 2017 decreased to 59.62/105 persons with an EAPC of −2.15 (95% CI: 2.21 to −2.09) and 1856.61/105 persons with an EAPC of −2.58 (95% CI: 2.64 to −2.51), respectively compared to those in 1990. Ambient PM2.5-attributable Non-communicable diseases (NCDs) have dominated major concern in middle and low SDI countries especially in South Asia and East Asia, while household PM2.5-attributable lower respiratory infections (LRIs) still caused the largest burden in low SDI countries in Africa and Asia. Those under 5 and over 70 years old had the largest burdens in PM2.5 attributable LRI and NCDs, respectively.
In conclusion, ambient PM2.5-attributable NCDs have threatened public health in middle and low SDI countries, while household PM2.5-attributable LRI still caused the largest burden in low SDI countries. More positive strategies should be tailored to reduce PM2.5-attributable burdens considering specific settings globally.
•PM2.5-attributed disease burdens transitioned from LRI to NCDs, with the greatest burden in regions with lower SDI.•Although ASR of death and DALY decreased, overall PM2.5-attributed disease burdens remain heavy.•Increasing ambient PM2.5-attributed non-communicable diseases primarily imperiled the health of older people.•Decreasing household PM2.5-attributed lower respiratory infection still dominated in children under 5 in low SDI regions.
Abstract
Various platinum-free electrocatalysts have been explored for hydrogen evolution reaction in acidic solutions. However, in economical water-alkali electrolysers, sluggish water dissociation ...kinetics (Volmer step) on platinum-free electrocatalysts results in poor hydrogen-production activities. Here we report a MoNi
4
electrocatalyst supported by MoO
2
cuboids on nickel foam (MoNi
4
/MoO
2
@Ni), which is constructed by controlling the outward diffusion of nickel atoms on annealing precursor NiMoO
4
cuboids on nickel foam. Experimental and theoretical results confirm that a rapid Tafel-step-decided hydrogen evolution proceeds on MoNi
4
electrocatalyst. As a result, the MoNi
4
electrocatalyst exhibits zero onset overpotential, an overpotential of 15 mV at 10 mA cm
−2
and a low Tafel slope of 30 mV per decade in 1 M potassium hydroxide electrolyte, which are comparable to the results for platinum and superior to those for state-of-the-art platinum-free electrocatalysts. Benefiting from its scalable preparation and stability, the MoNi
4
electrocatalyst is promising for practical water-alkali electrolysers.
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