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Glycerol, as the major by‐product of biodiesel, can be oxidized into diverse value‐added chemical products via either traditional chemical methods or electrochemical routes. Electrocatalytic glycerol oxidation reaction (GOR) driven by renewable‐derived electricity (e.g., wind and solar) is a promising pathway for fine chemicals production. In an electrochemical cell, GOR can be coupled with various cathodic reactions, including hydrogen evolution reaction (HER), CO2 reduction reaction (CO2RR), and oxygen reduction reaction (ORR); in this manner, different benefits of either energy effectiveness or additional value‐added products can be obtained depending on the cathode reduction reaction selected. Comprehensively understanding of electrocatalytic GOR and the associated processes is of great significance to promote its industrial application. Herein, recent progress of GOR is focused on. The background of biomass‐derived glycerol valorization to energy and value‐added chemicals as well as the electrochemical conversion techniques via GOR is introduced. Then, the electrocatalytic reaction pathways, the potential application of GOR, and the measurement method for products are also discussed and summarized. Special emphasis is put on the design and the development of high‐selectivity and high‐activity electrocatalysts for GOR. Finally, the challenges and the future prospects in the fields of GOR are highlighted. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable batteries have attracted attention owning to their advantages of safety, low cost, and sustainability, while the limited electrochemical stability window (1.23 V) of water leads to their failure in competition with organic‐based lithium‐ion batteries. Herein, we report an alkali–acid Zn–PbO2 hybrid aqueous battery obtained by coupling an alkaline Zn anode with an acidic PbO2 cathode. It shows the capability to deliver an impressively high open‐circuit voltage (Voc) of 3.09 V and an operate voltage of 2.95 V at 5 mA cm−2, thanks to the contribution of expanding the voltage window and the electrochemical neutralization energy from the alkali–acid asymmetric‐electrolyte hybrid cell. The hybrid battery can potentially deliver a large area capacity over 2 mAh cm−2 or a high energy density of 252.39 Wh kg−1 and shows almost no fading in area capacity over 250 charge–discharge cycles. [ABSTRACT FROM AUTHOR]

Metal ion hybrid capacitors (MIHCs) have been recognized as one of the most promising power sources owing to their combined merits of high energy density in batteries and high power output in supercapacitors. The kinetics mismatch between the capacitor-type cathode and battery-type anode yet must be well addressed before implementing their practical feasibility. Here, we overview the recent progress in sodium and potassium ion hybrid capacitors (SIHCs and PIHCs) and discuss the major challenges and give an outlook on the future directions in this field. The fundamental knowledge and the history will be firstly introduced, and special emphasis is then laid on the development of a variety of electrode materials in recent years. The prospects of future research of MIHCs are finally proposed towards their practical applications. We wish that this feature article can not only educate newcomers starting their reasearch in this field, but also inspire experieced researchers to contribute to the development of high-performance MIHC devices. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) monometallic pnictogens (antimony or Sb, and bismuth or Bi) nanosheets demonstrate potential in a variety of fields, including quantum devices, catalysis, biomedicine and energy, because of their unique physical, chemical, electronic and optical properties. However, the development of general and high‐efficiency preparative routes toward high‐quality pnictogen nanosheets is challenging. A general method involving a molten‐salt‐assisted aluminothermic reduction process is reported for the synthesis of Sb and Bi nanosheets in high yields (>90 %). Electrocatalytic CO2 reduction was investigated on the Bi nanosheets, and high catalytic selectively to formate was demonstrated with a considerable current density at a low overpotential and an impressive stability. Bi nanosheets continuously convert CO2 into formate in a flow cell operating for one month, with a yield rate of 787.5 mmol cm−2 h−1. Theoretical results suggest that the edge sites of Bi are far more active than the terrace sites. [ABSTRACT FROM AUTHOR]

Development of low cost electrocatalysts with outstanding catalytic activity and stability for oxygen evolution reaction (OER) in acid is a major challenge to produce hydrogen energy from water splitting. Herein, a novel metal‐free electrocatalyst consisting of a oxygen‐functionalized electrochemically exfoliated graphene (OEEG) nanosheets array is reported. Benefitting from a vertically aligned arrays structure and introducing oxygen functional groups, the metal‐free OEEG nanosheets array exhibits superior electrocatalytic activity and stability toward OER with a low overpotential of 334 mV at 10 mA cm−2 in acidic electrolyte. Such a high OER performance is thus far the best among all previously reported metal‐free carbon‐based materials, and even superior to commercial Ir/C catalysts (420 mV at 10 mA cm−2) in acid. Characterization results and electrochemical measurements identify the COOH species in the OEEG acting as active sites for acidic OER, which is further supported by atomic‐scale scanning transmission electron microscopy imaging and electron energy‐loss spectroscopy. Density functional theory calculations reveal that the reaction pathway of dual sites that is mixed by zigzag and armchair edges (COOH‐zig‐corner) is better than the pathway of single site. [ABSTRACT FROM AUTHOR]

Charge carriers separation and surface catalytic reactions are two crucial steps in photocatalytic processes; the rational design of photocatalysts by taking these two factors into consideration is thus of great importance to advance the associated performance. Herein, a self‐sacrificial strategy is developed to fabricate a ternary nanostructure photocatalyst, forming a hierarchical architecture of In(OH)3 nanocube decorated NiS‐ZnIn2S4 (ZIS) hybrid nanosheets (ZIS/In(OH)3‐NiS). Such a unique structure provides the hybrid photocatalyst with a facilitated path for efficiently separating the charge carrier and abundant sites for catalytic reactions. Systematic characterizations that reveal the strong electronic interactions in the ternary ZIS/In(OH)3‐NiS leads to fast electron transfer from excited ZnIn2S4 to NiS nanosheets, which provide catalytic sites for hydrogen evolution reaction. The comprehensive photocatalysis studies demonstrate that ZnIn2S4/In(OH)3‐NiS exhibits ultrahigh photocatalytic activity toward hydrogen generation with a high rate of 7010 μmol g−1 h−1, which ranks as one of the highest among ZnIn2S4‐based photocatalysts reported so far. This work provides an attractive and effective way to develop high‐activity photocatalysts without using precious metal cocatalysts. The investigation brings us one step closer to understanding the structure‐determining properties of nanohybrid architecture, and provides a valuable reference to develop cost‐effective and practical photocatalysts for a variety of applications. [ABSTRACT FROM AUTHOR]

Conversing CO2 into value‐added chemicals endows electrochemical CO2 reduction reaction (CO2RR) with the potential to tackle over issues induced by the increased CO2 level in the atmosphere. The associated technological viability of this process is highly dependent on exploring efficient electrocatalysts. In this work, we successfully synthesized nitrogen and sulfur co‐doped carbon nanosheets (NS‐CNSs), which are comprehensively characterized by a variety of characterization techniques. When used as the catalyst for CO2RR, the NS‐CNSs exhibit remarkably high catalytic activity and selectivity with a Faradaic efficiency of ∼85.4 % for CO production and long‐term durability. The superior performance of this material majorly originates from the unique nanosheets structure with large porosity and the co‐doped S and N in the nanosheets, which exposed larger electrochemical activity surface areas and more active sites for promoting CO2 reduction. [ABSTRACT FROM AUTHOR]

It remains great challenge to develop precious‐metal‐free electrocatalysts to implement high‐activity electrochemical conversion of O2 into value‐added hydroperoxide species (HO2−), which are vulnerable when exposed to various transition‐metal‐based catalysts. A strategy based on steric hindrance and layered nickel‐based layered double hydroxide (Ni‐LDH) induction has been developed for one‐pot inlaying high‐density ultrathin 2 D Ni‐LDH chips on in situ‐grown carbon nanosheets (Ni‐LDH C/CNSs). The resulting material exhibits high electrocatalytic selectivity with a faradaic efficiency up to 95 % for oxygen reduction into peroxide and attains a fairly high mass activity of approximately 22.2 A g−1, outperforming most metal‐based catalysts reported previously. Systematic studies demonstrate that the greatly increased defect concentration at Ni edge sites of Ni‐LDH chips results in more active sites, which contributes a favorable thermodynamically neutral adsorption of OOH* and adsorbed H2O2 molecules relatively weakly. Additionally, the modified CNSs effectively suppress H2O2 decomposition and avoid O−O bond cleavage to produce H2O by steric effects. The synergistic effect of CNSs and Ni‐LDH chips therefore leads to high activity and high selectivity in a two‐electron pathway. A proof‐of‐concept zinc–air fuel cell is proposed and set up to demonstrate the feasibility of green synthesis of peroxide, generating an impressive H2O2 production rate of 5239.67 mmol h−1 gcat.−1. [ABSTRACT FROM AUTHOR]

We report a straightforward strategy to design efficient N doped porous carbon (NPC) electrocatalyst that has a high concentration of easily accessible active sites for the CO2 reduction reaction (CO2RR). The NPC with large amounts of active N (pyridinic and graphitic N) and highly porous structure is prepared by using an oxygen‐rich metal–organic framework (Zn‐MOF‐74) precursor. The amount of active N species can be tuned by optimizing the calcination temperature and time. Owing to the large pore sizes, the active sites are well exposed to electrolyte for CO2RR. The NPC exhibits superior CO2RR activity with a small onset potential of −0.35 V and a high faradaic efficiency (FE) of 98.4 % towards CO at −0.55 V vs. RHE, one of the highest values among NPC‐based CO2RR electrocatalysts. This work advances an effective and facile way towards highly active and cost‐effective alternatives to noble‐metal CO2RR electrocatalysts for practical applications. [ABSTRACT FROM AUTHOR]

Development of cost‐effective and highly efficient oxygen evolution reaction (OER) electrocatalysts has become a vital project of renewable energy technologies. The OER is critical for a variety of electrochemical energy devices such as water electrolyzers, metal‐air batteries, CO2 reduction, and electrosynthesis of ammonia. Compared to extensively studied metal oxide catalysts, graphitized carbon catalysts have been newly emerged as promising OER catalysts especially in less corrosive alkaline media, due to their low cost, high electrical conductivity, unique physicochemical properties, and excellent electrocatalytic performances. In this review, we discussed recent advances in nanostructured carbon electrocatalysts. At first, metal‐free OER carbon electrocatalysts including single‐ and multi‐heteroatom doping and edge‐ and defect‐rich defects are introduced. Then, transition metal and heteroatom co‐doped nanocarbons are summarized including Co−N−C, Ni−N−C, and Fe‐N−C. In addition, carbon based hybrid electrocatalysts are highlighted, which include carbon based transition metal nitrides (TMNx), sulfides (TMSx), and selenides (TMSex), and phosphides (TMPx). Finally, current challenges and perspective for future research on carbon‐based OER catalysts are outlined. [ABSTRACT FROM AUTHOR]

NH3 synthesis via the electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions has been regarded as a sustainable strategy for fertilizer production and hydrogen fuel storage and mitigating greenhouse gas emissions. The faradaic efficiency (FE) and reaction rate of the NRR, however, are still low for current electrocatalysts. Herein, we develop a metal-free B, N co-doped porous carbon nanofiber (B/N–CNF) that exhibits superior electrocatalytic performance for the NRR in an alkaline electrolyte with the highest FE of 13.2% at −0.5 V and a NH3 yield rate of 32.5 μg h−1 mgcat.−1 at −0.7 V. Such a high NRR activity of the B/N–CNF is superior to that of N- or B-doped carbon materials in the literature. The experimental results reveal that the B–N bonds play a critical role in the NRR process, in which N atoms promote the electron conductivity and B atoms efficiently enhance the N2 adsorption and charge transfer. [ABSTRACT FROM AUTHOR]

The electrochemical carbon dioxide (CO2) reduction (ECR) represents one of the most promising technologies for CO2 conversion into value-added feedstock from carbon monoxide (CO) to a variety of hydrocarbons. As the raw material for Fischer–Tropsch synthesis, CO is one of the most desirable ECR products and has recently received extensive research attention. Although noble metal materials, such as Au and Ag, show high selectivity towards conversion of CO2 to CO, their relative scarcity and high cost seriously limit their practical commercial application. Nanostructured carbon-based non-precious metal electrocatalysts (Nano-CNMs) are of tremendous interest in the field of ECR catalysis due to their tunable structures and electronic properties. Herein, we present an overview of recent progress in the application of Nano-CNMs, mainly including heteroatom-doped carbon, transition metal–heteroatom co-doped carbon, and carbon-based hybrid materials, with emphasis on electrocatalytic conversion of CO2 to CO. We particularly focus on discussing the structure/composition–performance relationships with regard to the electronic structure, surface properties, doping content, and associated electrocatalytic performance of various Nano-CNMs. We outline the future research directions in the development of high-selectivity ECR electrocatalysts for CO production and the stringent challenges in fundamental research and industrial application. [ABSTRACT FROM AUTHOR]

Sodium dual-ion batteries (SDIBs) have received tremendous research attention due to their multiple advantages of environmental friendliness and high working voltages. However, the development of high-performance SDIBs still remains a daunting challenge, mainly due to the lack of robust anode materials with sufficient interlayer spacing for Na+ insertion/extraction. We here report a solvothermal method for the fabrication of coral-like nanohybrids that are constructed from layer-by-layer stacked nitrogen and sulfur co-doped carbon film modified atomic MoS2 nanosheets (a-MoS2NS@NSCfilm). Comprehensive characterization demonstrates that a-MoS2NS@NSCfilm shows favorable electrochemical and structural properties for sodium ion storage, including significantly improved electrical conductivity and an expanded layer space of 0.95 nm thanks to carbon film modification, which favorably facilitate electron transfer and enhance Na+ diffusion kinetics, thus leading to an impressive capability for fast and high-capacity sodium storage. We further verify the practical application of a-MoS2NS@NSCfilm as an anode for SDIBs by coupling it with an expanded graphite (EG) cathode; this delivers a capacity of 40 mA h g−1 with outstanding cycling stability and an extremely low capacity decay of 0.0056% per cycle after 5000 cycles at 10C. [ABSTRACT FROM AUTHOR]

It is highly attractive to develop efficient water electrolysis route to implement hydrogen generation in a low‐cost way, which while requires excess energy to surmount the activation barriers majorly limited by oxygen evolution reaction at anode side. Herein, we report an acid‐alkali asymmetric‐electrolyte electrolyzer (AAAE) that can achieve substantial energy saving for electrolysis hydrogen generation, thanks to the assistance of electrochemical neutralization energy (ENE) and urea oxidation reaction (UOR). To this end, free‐standing Ni(OH)2 nanosheets on carbon cloth (Ni(OH)2−NSs/CC) is fabricated as catalytic anode for alkaline UOR, which manifests impressively high catalytic activity with delivering 10 mA cm−2 at 1.32 V and long‐term durability. The as‐developed AAAE only requires an applied voltage of 0.66 V to release the electrolysis current of 10 mA cm−2, yielding the H2 Faraday efficiency close to 100 % along with H2 production rate of 183.8 μmol h−1. [ABSTRACT FROM AUTHOR]

The development of high-kinetic catalysts for the hydrogen evolution reaction (HER) in a neutral electrolyte is of great importance but unfortunately remains a challenge so far. Herein, we report hybrids with abundant Ru–S–Sb bonds and engineered ultrathin antimonene (Ru–S–Sb/antimonene) as highly kinetic, active, stable electrocatalysts for the HER in an aqueous neutral electrolyte. Experiments and density functional theory (DFT) calculations reveal that Ru–S–Sb bonds coupling with antimonene synergistically work to promote HER activity. The present study brings us one step closer to understand the structure–composition–property relationships and practical electrolytic H2 production. [ABSTRACT FROM AUTHOR]

Developing efficient and low‐cost catalysts with excellent catalytic activities for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of significance for large‐scale commercial applications in rechargeable Zn−air batteries and fuel cells. Herein, we develop a simple, mild and efficient method to synthesize a hybrid of N‐doped carbon nanosheets encapsulating cobalt nanoparticles (Co@NCNSs), which shows favorable catalytic properties toward both ORR and OER with high activity and good stability. The optimized hybrids (Co@NCNSs‐900) exhibit an onset potential of 0.95 V vs. reversible hydrogen electrode (RHE) and a half‐wave potential of 0.85 V vs. RHE for the ORR, and an onset potential of 1.51 V vs. RHE, a potential of 1.59 V vs. RHE at 10 mA cm−2 for the OER, as well as an oxygen electrode activity parameter (ΔE) of 0.802 V in alkaline electrolyte. Moreover, the Zn−air battery with the Co@NCNSs‐900 as the cathode catalyst outperforms that with the commercial Pt/C as cathode catalyst in terms of the maximum power density and stability, showing great prospects in renewable energy applications. [ABSTRACT FROM AUTHOR]

Transition-metal nitrides have captured extensive attention for battery applications ascribed to their high electrical conductivity and considerable capacity, whilst sluggish kinetics constrains their rate capability and thus limited their practical applications in lithium or sodium ion batteries (LIBs or SIBs). Herein, we report an effective approach to prepare nanohybrids of vanadium nitride quantum dots that were uniformly embedded within porous shells of N-doped carbon hollow spheres (VNQD@NC HSs). These manifest attractive advantages as anodes of LIBs and SIBs with facilitated transfer for both electron and Li+/Na+ and robust structural integrity, primarily benefiting from structural features of interior voids, N-doped carbon matrix, and quantum dot level of VN active material. Accordingly, the VNQD@NC HSs electrode can deliver a reversible capacity of up to 832 mA h g−1 at a current density of 0.1 A g−1 after 200 cycles, along with a high rate performance of 378 mA h g−1 at 6.4 A g−1 for LIBs. And for SIBs, the VNQD@NC HSs also retains a capacity of 361 mA h g−1 at a current density of 0.1 A g−1 after 200 cycles and a reversible capacity of 306 mA h g−1 over 1400 cycles at 1 A g−1. [ABSTRACT FROM AUTHOR]

There remains a grand challenge to develop sustainable and pollution-free energy to replace the current dominant but gradually “depleting” fossil fuels. Electrochemical energy conversion presents a promising “bridge” to mitigate energy shortage issues and minimize the ecological implications by synergy with the ever-increasing sustainable energies (e.g., wind and solar). It thus calls for exploring high-activity, low-cost, and long-durability electrocatalysts to facilitate the electrochemical reactions involved in electrochemical energy conversion systems. This review focuses on summarizing the recent progress in the development of bifunctional electrocatalysts for several important electrochemical redox reactions which are critical to implement conversion between electrical energy and chemical energy, especially for bifunctional electrocatalysts applied in a single electrochemical conversion system, including water electrolyzers with the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), zinc–air batteries with the OER and oxygen reduction reaction (ORR), and fuel cells with small molecule (e.g., glucose, urea, and hydrazine hydrate) oxidation reactions (MOR) and the ORR. Special emphasis has been placed on investigating the progress of electrocatalyst synthesis and strategies for improving the electrocatalytic performance and the associated devices' performance in terms of activity, stability, power density etc. We also put forward the major challenges and prospects in the development of bifunctional electrocatalysts for potential applications in a variety of energy devices. [ABSTRACT FROM AUTHOR]

Abstract We here report the fabrication of a core-shell WO 3 @ZnIn 2 S 4 heterostructure by an interfacial seeding growth strategy, which is implemented by direct growth of ZnIn 2 S 4 nanosheets on the surface of WO 3 nanorods with forming a strong electronic interaction between two semiconductors that are beneficial for promoting the interfacial charge transfer. Systematic studies demonstrate that the WO 3 @ZnIn 2 S 4 nanohybrids hold superior performance for photocatalytic hydrogen generation under visible light irradiation with a production rate of 3900 μmol g−1 h−1. This work provides an effective approach to construct the direct Z-scheme photocatalytic systems for efficient photocatalytic hydrogen evolution, which would be significant for the design of more direct Z-scheme system for various photocatalytic applications. [ABSTRACT FROM AUTHOR]

Sodium-ion hybrid capacitors (SIHCs) have shown great promise in achieving both high energy density and high power density by virtue of synergizing the merits of batteries and capacitors. However, the lack of favorable anode material with superior sodium-ion storage capability is still a major challenge in the development of high-performance SIHCs. Herein, we report the design and synthesis of a promising sodium-ion storage nanohybrid with FeS quantum dots embedded in three-dimensional (3D) inverse opal (IO)-structured N-doped carbon (3D-IO FeS-QDs@NC). By virtue of the robust 3D conductive architecture, the 3D-IO FeS-QDs@NC nanohybrid exhibits favorable features of excellent electron/ion transport kinetics, superior structural stability, as well as impressive sodium-ion storage capability with high specific capacity, outstanding rate capability, and ultra-long cyclic stability. Such highly desirable sodium storage performance inspired us to study their potential application in SHICs by coupling with commercial activated carbon (AC) as a cathode. The as-developed SHICs can deliver a maximum energy density and power output of 151.8 W h kg−1 and 9280 W kg−1, respectively, and an excellent cycling lifespan with 91% capacity retention after 5000 cycles at 1 A g−1, which holds promise for bridging the performance gap between conventional batteries and capacitors. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR), as one of the most critical but promising reactions for energy conversion, has attracted increasing research interest. Recent reports have evidenced that carbonization of heteroatoms doped porous organic polymers (POPs) is an effective approach toward highly efficient ORR electrocatalysts. We herein report a versatile ternary copolymerization strategy to synthesize stable POPs gel with tunable doping of heteroatoms (N, S, F) and Fe species, leading to significant enhancement in surface area and porosity. Carbonization of these POPs afford efficient ORR electrocatalyst with optimized composition, hierarchical porous structure and prominent catalytic activities in both alkaline and neutral conditions. The optimized catalyst (TF‐C‐900) exhibited an onset potential (Eonset) of 1.01 V and half‐wave potential (E1/2) of 0.88 V in 0.1 M KOH solution. These performance metrics are even comparable to those of the Pt/C (0.99 and 0.85). In addition, the TF‐C‐900 also showed superior stability and advantage of methanol tolerance, enabling them to be a competitive cathode electrocatalysts for alkaline fuel cell. Porous organic polymer gels synthesized via ternary polymerization were used to fabricate heteroatom‐doped catalysts for the oxygen reduction reaction and as cathode material in Zn‐air batteries. The porous structure showed prominent catalytic activity under both alkaline and neutral conditions, superior stability and advantage of methanol tolerance, enabling them to be a competitive cathode electrocatalysts for alkaline fuel cell. [ABSTRACT FROM AUTHOR]

Abstract: Developing cost‐effective electrocatalysts for high‐selectivity CO2 electroreduction remains challenging. We herein report a perfluorinated covalent triazine framework (CTF) electrocatalyst that displays very high selectivity in the electroreduction of CO2 to CH4 with a faradaic efficiency of 99.3 % in aqueous electrolyte. Systematic characterization and electrochemical studies, in combination with density functional theory calculations, demonstrate that the presence of both nitrogen and fluorine in the CTF provides a unique pathway that is inaccessible with the individual components for CO2 electroreduction. [ABSTRACT FROM AUTHOR]

Although the fundamental processes of electrolytic hydrogen generation are relatively well understood, fundamental studies and explorations of the new concepts and materials for electrolysis are highly desirable to make renewable hydrogen sufficiently cost-competitive. Herein, we report a proof-of-concept for an alkaline–acid-based hydrogen generating hydrazine fuel cell by coupling the hydrazine oxidation reaction (HzOR) at the alkaline anode with the hydrogen evolution reaction (HER) at the acidic cathode. Furthermore, we verified that such a hybrid cell could simultaneously fulfill hydrogen production and electricity generation owing to harvesting of two types of electrochemical energies, i.e., electrochemical energy of the HzOR and the electrochemical neutralization energy. To this end, a bifunctional electrode comprising a three-dimensional nanoporous Ni–Co perselenide nanorod array (NixCo1−xSe) was designed and prepared by a facile two-step synthesis process, involving the initial in situ electroplating on a carbon cloth followed by subsequent selenization. The optimized electrode, i.e., Ni0.5Co0.5Se2, showed high electrocatalytic activity toward HzOR in alkaline electrolyte and HER in acidic medium. The optimized alkaline–acid hydrazine fuel cell, with the Ni0.5Co0.5Se2 electrode as both the cathode and anode, could potentially deliver a power density of 13.3 mW cm−2 at a current density of 54.7 mA cm−2 with good long-term stability and a faradaic efficiency of nearly 100% for hydrogen production. [ABSTRACT FROM AUTHOR]

Abstract: Sodium‐ion batteries (SIBs) have recently attracted increasing attention as the promising alternative to lithium‐ion batteries due to their multiple advantages of abundant reserves and low cost. However, the development of highly desirable anode materials suitable for SIBs is still hampered by a rather low capacity, poor rate capability, and cycling stability. Herein, a deliberate design to implement reliable and simple fabrication of an inverse opal structured nanohybrid of carbon‐confined various transition metal sulfides quantum dots (QDs) is presented. Comprehensive characterizations demonstrate that the hybrids hold a 3D architecture with uniform dispersion of QDs in a conductive carbon matrix that in turn encapsulates these quantum dots. With Co9S8 as an example, such a unique architecture, when applied as the anode of SIBs, endows the hybrids with multiple advantages including a high reversible specific capacity, extraordinary high rate capability, and excellent durability over 2000 cycles charging–discharging process. [ABSTRACT FROM AUTHOR]

Developing high-active, good-stable, and cost-effective electrocatalyst for oxygen reduction reaction (ORR) in all-pH medium is highly desired for the application of various fuel cell systems. Here, a network architecture hybrid with porous nitrogen-doped graphene encapsulated β-FeOOH nanoparticals (β-FeOOH/PNGNs) as ORR electrocatalyst, which exhibits remarkable enhancement ORR performance in terms of activity and stability in pHuniversal medium is reported. Systematic characterization combining with X-ray absorption fine structure analysis and the first principles simulations reveal that the as-formed surface FeO6 active sites that induced by a mass of Fe vacancies in β-FeOOH/PNGNs can significantly lower the thermodynamic barrier of the total reaction, and hence contribute to a remarkable enhancement in ORR activity. [ABSTRACT FROM AUTHOR]

We report the fabrication of self-supported Cu/Cu2O–CuO/rGO nanowire arrays on commercial porous copper foam, which exhibit excellent activity and durability for electrochemical hydrogen evolution, presenting a small onset potential of 84 mV and a low overpotential of 105 mV at a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Abstract: Here, we reported the synthesis of a three‐dimensional (3D) interconnected network nanostructure of reduced graphene oxide (rGO), enwrapping mesoporous ZnS nanospheres (m‐ZnS NSs@rGO). The synthesis is implemented by a simple gelatin‐assisted hydrothermal reaction followed by self‐assembly between mesoporous ZnS NSs and rGO. As a result of the synergic effect of the special nanostructure of ZnS nanospheres and rGO enwrapping, the m‐ZnS NSs@rGO composite exhibits favorable features as anode material in sodium‐ion batteries. These features include good cycling stability (513 mAh g−1 at 0.1 A g−1 after 80 cycles) and good rate capability (320 mAh g−1 at 1 A g−1). The 3D conductive structure, in conjunction with the mesoporous ZnS nanoparticles, provide advantageous features to the hybrids to buffer volume expansion/contraction upon the sodiation/desodiation process and facilitate mass (ions and electron) transportation and electron transfer. [ABSTRACT FROM AUTHOR]

The heteroporous MoS2/Ni3S2 catalyst exhibits excellent electrocatalytic activity for the overall urea splitting with only a cell voltage of 1.45 V at 20 mA cm−2 in 1 M KOH with 0.33 M urea. This value is the best of all the bifunctional urea splitting electrocatalysts, including Pt, reported to date. [ABSTRACT FROM AUTHOR]

Abstract: An alkaline–acid Zn–H2O fuel cell is proposed for the simultaneous generation of electricity with an open circuit voltage of about 1.25 V and production of H2 with almost 100 % Faradic efficiency. We demonstrate that, as a result of harvesting energy from both electrochemical neutralization and electrochemical Zn oxidation, the as‐developed hybrid cell can deliver a power density of up to 80 mW cm−2 and an energy density of 934 Wh kg−1 and maintain long‐term stability for H2 production with an output voltage of 1.16 V at a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite solar cells have delivered power conversion efficiency beyond 22% in less than seven years, implying the potential for the paradigm shift of low‐cost photovoltaics with high efficiency and low embedded energy. Besides the “perovskite fever,” the development of new hole transport materials (HTM), especially dopant‐free HTMs, is another research hotspot. This is because the currently used HTMs, such as spiro‐OMeTAD derivatives, require additional chemical doping process to ensure sufficient conductivity and proper ionic potential level for efficient hole transport and collection. However, the commonly used dopants are volatile and hygroscopic which not only increase the complexity and cost of device fabrication but also deteriorate the device stability. So far, there have been several reviews on new HTMs, but review or analysis on dopant‐free HTMs is scarce. In this review, all reported dopant‐free HTMs are categorized into four primary different types and lessons will be learned during the separate discussions. The stability test behavior of all the intrinsic HTMs will be evaluated directly. In the end, the correlations between the properties of the intrinsic HTMs and parameters of the devices will be plotted to shed light on the future direction of development of this field. [ABSTRACT FROM AUTHOR]

The ability to reduce the energy consumed and the cost in water splitting is crucial for the generation of hydrogen, which can be stored and then oxidized to deliver clean, abundant, and sustainable energy with the regeneration of water. Herein, we report an asymmetric electrolyzer with three-dimensional (3D) Ni2P nanorod networks as bifunctional electrocatalysts for acidic cathode and alkaline anode that are separated by a bipolar membrane; this type of electrolyzer affords us with optimization in decreasing the energy required and maximizing the electrocatalysts: (1) pH gradient between an anolyte and a catholyte separated by a bipolar membrane provides the electrolyzer with additional electrochemical neutralization energy for facilitating water splitting and (2) efficiency of electrocatalysts can be maximized by offsetting the well-known mismatch of optimal conditions for electrocatalysts between the anode (normally alkaline) and the cathode (generally acidic). This unprecedented water electrolysis system can activate water splitting at an applied voltage of around 0.79 V that is significantly lower than the minimum theoretical voltage requirement (1.23 V), reducing electricity energy consumed by more than 35.8%. [ABSTRACT FROM AUTHOR]

An unprecedented asymmetric-electrolyte electrolyzer is proposed using an acidic cathode for the hydrogen evolution reaction (HER) and an alkaline anode for the urea oxidation reaction (UOR), which significantly decreases the electrical energy required for electrolytic hydrogen production. [ABSTRACT FROM AUTHOR]

Abstract: Zn−air batteries have attracted enormous research interest, driven by the promise for vehicle propulsion owing to their advantages of high‐level safety, low cost, and high specific energy density. Here, we report an asymmetric‐electrolyte Zn−air battery with acid catholyte and alkaline anolyte separated by a bipolar membrane. We demonstrate that the as‐designed Zn−air battery, thanks to the as‐formed concentration cell, can deliver a maximum power density of 380 mW cm−2 and a specific energy density of 1522 Wh kg−1 with an open‐circuit voltage of 2.25 V. The as‐proposed Zn−air battery performance is superior to the conventional Zn−air battery in terms of these pivotal performance parameters. [ABSTRACT FROM AUTHOR]

A strategy was developed to fabricate a set of MnO@C nanohybrids with MnO nanoparticles (NPs) embedded in an ultrathin three-dimensional (3D) carbon framework for use as anode materials for lithium-ion batteries (LIBs). The 3D carbon frameworks provide MnO NPs with electrical pathways and mechanical robustness, which efficiently improved the reaction kinetics, prevented the MnO from fracturing and agglomerating, and limited the formation of a solid electrolyte interface (SEI) at the MnO-electrolyte interface. Benefitting from the unique 3D framework structure, the MnO/C nanohybrids carbonized at 500 °C exhibited a highly reversible specific capacity of 1,420 mAh·g at 0.2 A·g, excellent cycling stability with 98% capacity retention, and enhanced rate performance of 680 mAh·g at 2 A·g. The feasibility of the large-scale production of such MnO/C nanohybrids, associated with their outstanding Li-ion storage properties, opens a promising avenue for the development of high-performance anodes for nextgeneration LIBs. [ABSTRACT FROM AUTHOR]

Abstract: Hybrids of Fe/Fe3C embedded in N‐doped carbon nanotubes (Fe/Fe3C@NCNTs) are prepared by pyrolyzing mixtures of Fe3O4 nanoparticles and dicyandiamide. The systematic electrochemical study of Fe/Fe3C@NCNTs shows a decent catalytic activity toward the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The sample of Fe/Fe3C@NCNTs at 750 °C exhibits a remarkably high activity with an onset potential of 1.47 V for the OER, and an onset potential of 0.96 V and half‐wave potential 0.88 V for the ORR, which inspired us to set up a rechargeable Zn‐air battery with such Fe/Fe3C@NCNT nanohybrids as the cathode materials, showing a maximum power density of 198 mW cm−2 and long‐term stability after 500 cycles. We also demonstrate that Fe/Fe3C@NCNTs present favorable electrocatalytic activity towards the CO2 reduction reaction (CO2RR) with a low onset potential and good selectivity. The major products are a mixture of H2 and CO gases that can be used for methanol production in the Fischer−Tropsch process. [ABSTRACT FROM AUTHOR]

The development of high-activity electrocatalysts for water splitting that comprise only inexpensive, earth-abundant elements is critical but remains a daunting challenge. In this work, yolk-shell Ni3Fe/Ni3FeN was prepared by a spray-pyrolysis technique, which could be scaleable. The yolk-shell Ni3Fe/Ni3FeN presents excellent catalytic activity for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) with overpotentials of 268 and 166 mV at 10 mA cm−2, respectively, and bears a prominent electrochemical durability. Overall water splitting with an electrolyzer containing the yolk-shell Ni3Fe/Ni3FeN as the cathode and anode only requires a cell voltage of 1.62 V to reach a current density of 10 mA cm−2. The present research not only introduces a new route for the synthesis of advanced functional electrocatalysts for overall water splitting but also sheds light on their potential commercial applications. [ABSTRACT FROM AUTHOR]

Two nitrogen-rich porous organic polymers (POPs) were prepared via facile and low-cost Schiff base chemistry with ferrocene (Fc) and melamine/melem as building blocks. Carbonization of these POP precursors results in porous carbon nanohybrids with carbon composites containing crystalline Fe3C/Fe. Characterization based on a variety of techniques demonstrates that the porous carbon nanohybrids feature rich-nitrogen doping, good conductivity and high BET surface area with unique porous structure, endowing them with an excellent catalytic activity toward the oxygen reduction reaction (ORR) in alkaline electrolytes. The catalysts obtained by carbonization at 800 °C (N-Fc-800) exhibit favorable activity with a rather high onset potential and half wave potential of 0.96 and 0.82 V, respectively. Furthermore, a rechargeable zinc-air battery was assembled using the N-Fc-800 as the cathode catalyst. Compared with the commercial Pt/C, the N-Fc-800 based battery displays a considerably high power density of 178 mW cm−2 with a smaller charge–discharge voltage gap of 0.94 V, and holds excellent stability with a less activity decay (1.0%) over long charge–discharge cycles (200 cycles). [ABSTRACT FROM AUTHOR]

Nanohybrids with hollow CoNiP nanoparticles decorating reduced graphene oxide (h-CoNiP/rGO) are prepared by a low-temperature phosphorization method. The h-CoNiP/rGO present favorable electrocatalytic advantages toward the oxygen evolution reaction (OER) in alkaline solution, including an onset potential of 1.44 V, a low overpotential of 280 mV at a current density of 10 mA cm − 2 , a small Tafel slope of 65.2 mV dec − 1 , and pretty good durability. The use of earth-abundant elements in a high-activity OER electrocatalyst may provide an effective way of advancing the development of full water splitting. [ABSTRACT FROM AUTHOR]

Electrocatalytic carbon dioxide reduction reaction (CO2RR) is a promising strategy to mitigate or to address the issues caused by increasing CO2 emissions, but the implementation of such a technique highly depends on the exploration of highly efficient electrocatalysts toward the CO2RR. Here, we report a reliable route for the synthesis of hollow CuS microcubes (h-CuS MCs) through a galvanic replacement reaction of the Cu2O microcube (Cu2O MC) precursor. A variety of characteristic techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy, were performed to study the morphology, crystalline structure, and surface properties. Systematic electrochemical studies demonstrate that the electrocatalytic activity for CO2RR is sensitive to crystalline structure, morphology, and size of Cu-based materials. The h-CuS MCs manifest the highest electrocatalytic activity upon electrocatalyzing CO2RR among the set of Cu-based materials tested, as evidenced by a rather low overpotential and an enhanced faradaic efficiency for CO production. [ABSTRACT FROM AUTHOR]

Exploring high-performance electrocatalysts is of great importance for developing clean and renewable energy conversion systems such as fuel cells and metal–air batteries. Hybrid nanostructures with transition metal nanoparticles embedded in a carbon matrix exhibit outstanding electrocatalytic activity and have emerged as promising low-cost alternatives to precious metal catalysts for a variety of electrochemical reactions. Herein, we report a convenient synthesis route to prepare a three-dimensional porous nanoarchitecture with Co nanoparticles (Co NPs) inlayed in nitrogen-doped macroporous carbon (Co/N-MC). The hybrids show an outstanding electrocatalytic activity for the oxygen reduction (ORR) and glucose oxidation reaction (GOR) due to the synergistic contribution of the Co NPs and nitrogen doping in macroporous carbon. Benefitting from their outstanding electrocatalytic activity in the ORR and GOR, a home-made glucose fuel cell (GFC) was set up using Co/N-MC as the anode and cathode material, delivering a considerable power density with decent stability. [ABSTRACT FROM AUTHOR]

Two redox-active porous organic frameworks (POFs) with a built-in radical moiety (TEMPO) and hierarchical porous structures were synthesized through a facile bottom-up strategy and studied as cathode materials for lithium-sulfur (Li−S) batteries. The sulfur loading in these two POFs reached 61 %, benefitting from their large pore volumes. Owing to the highly dense docking sites of TEMPO, sulfur could be covalently immobilized within the porous networks and efficiently inhibit the shuttle effect, thereby significantly improving the cycling performance. The composites TPE-TEMPO-POF-S (TPE=tetraphenylethene) deliver a capacity in excess of 470 mAh g−1 after 200 cycles with a coulombic efficiency of around 100 % at a current rate of 0.1 C. Furthermore, TEMPO-POFs with sulfur embedded showed excellent rate capability with limited capacity loss at rates of 0.1-1 C. [ABSTRACT FROM AUTHOR]