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In recent years, lithium oxygen batteries (Li-O 2 ) have received considerable research attention due to their extremely high energy density. However, the poor conductivity and ion conductivity of the discharge product lithium peroxide (Li 2 O 2 ) result in a high charging overpotential, poor cycling stability, and low charging rate. Therefore, studying and improving catalysts is a top priority. This study focuses on the commonly used heterogeneous catalyst ruthenium (Ru). The local distribution of this catalyst is controlled by using sputtering technology. Moreover, X-ray nanodiffraction is applied to observe the relationship between the decomposition of Li 2 O 2 and the local distribution of Ru. Results show that Li 2 O 2 decomposes homogeneously in liquid systems and heterogeneously in solid-state systems. This study finds that the catalytic effect of Ru is related to electrolyte decomposition and that its soluble byproducts act as electron acceptors or redox mediators, effectively reducing charging overpotential but also shortening the cycle life.

This review article discusses the recent advances in rechargeable metal-CO 2 batteries (MCBs), which include the Li, Na, K, Mg, and Al-based rechargeable CO 2 batteries, mainly with nonaqueous electrolytes. MCBs capture CO 2 during discharge by the CO 2 reduction reaction and release it during charging by the CO 2 evolution reaction. MCBs are recognized as one of the most sophisticated artificial modes for CO 2 fixation by electrical energy generation. However, extensive research and substantial developments are required before MCBs appear as reliable, sustainable, and safe energy storage systems. The rechargeable MCBs suffer from the hindrances like huge charging-discharging overpotential and poor cyclability due to the incomplete decomposition and piling of the insulating and chemically stable compounds, mainly carbonates. Efficient cathode catalysts and a suitable architectural design of the cathode catalysts are essential to address this issue. Besides, electrolytes also play a vital role in safety, ionic transportation, stable solid-electrolyte interphase formation, gas dissolution, leakage, corrosion, operational voltage window, etc. The highly electrochemically active metals like Li, Na, and K anodes severely suffer from parasitic reactions and dendrite formation. Recent research works on the aforementioned secondary MCBs have been categorically reviewed here, portraying the latest findings on the key aspects governing secondary MCB performances.

With magnesium being a cost-effective anode metal compared to the other conventional Li-based anodes in the energy market, it could be a capable source of energy storage. However, Mg-O 2 batteries have struggled its way to overcome the poor cycling stability and sluggish reaction kinetics. Therefore, Ru metallic nanoparticles on carbon nanotubes (CNTs) were introduced as a cathode for Mg-O 2 batteries, which are known for their inherent electronic properties, large surface area, and increased crystallinity to favor remarkable oxygen reduction reactions and oxygen evolution reactions (ORR and OER). Also, we deployed a first-of-its-kind, conducive mixed electrolyte (CME) (2 M Mg(NO 3 ) 2 :1 M Mg(TFSI) 2 /diglyme). Hence, this synergistic incorporation of CME-based Ru/CNT Mg-O 2 batteries could unleash long cycle life with low overpotential, excellent reversibility, and high ionic conductivity and also reduces the intrinsic corrosion behavior of Mg anodes. Correspondingly, this novel amalgamation of CME with Ru/CNT cathode has displayed superior cyclic stability of 65 cycles and a maximum discharge potential of 25 793 mAh g -1 with a small overvoltage plateau of 1.4 V, noticeably subjugating the findings of conventional single electrolyte (CSE) (1 M Mg(TFSI) 2 /diglyme). This CME-based Ru/CNT Mg-O 2 battery design could have a significant outcome as a future battery technology.

All-solid-state lithium-ion batteries (ASSLIBs) have attracted much attention owing to their high energy density and safety and are known as the most promising next-generation LIBs. The biggest advantage of ASSLIBs is that it can use lithium metal as the anode without any safety concerns. This study used a high-conductivity garnet-type solid electrolyte (Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 , LLZTO) and Li-Ga-N composite anode synthesized by mixing melted Li with GaN. The interfacial resistance was reduced from 589 to 21 Ω cm 2 , the symmetry cell was stably cycled for 1000 h at a current density of 0.1 mA cm -2 at room temperature, and the voltage range only changed from ±30 to ±40 mV. The full cell of Li-Ga-N|LLZTO|LFP exhibited a high first-cycle discharge capacity of 152.2 mAh g -1 and Coulombic efficiency of 96.5% and still maintained a discharge capacity retention of 91.2% after 100 cycles. This study also demonstrated that Li-Ga-N had been shown as two layers. Li 3 N shows more inclined to be closer to the LLZTO side. This method can help researchers understand what interface improvements can occur to enhance the performance of all-solid-state batteries in the future.

Solar-driven water electrolysis to produce hydrogen is one of the clean energy options for the current energy-related challenges. Si as a photocathode exhibits a large overpotential due to the slow hydrogen evolution reaction (HER) kinetics and hence needs to be modified with a cocatalyst layer. MoS 2 is a poor HER cocatalyst due to its inert basal plane. Activation of the MoS 2 basal plane will facilitate HER kinetics. In this study, we have incorporated SnS 2 into MoS 2 ultrathin sheets to induce defect formation and phase transformation. MoS 2 /SnS 2 composite ultrathin sheets with a Sn 2+ state create a large number of S vacancies on the basal sites. The optimized defect-rich MoS 2 /SnS 2 ultrathin sheets decorated on surface-modified Si micro pyramids as photocathodes show a current density of -23.8 mA/cm 2 at 0 V with an onset potential of 0.23 V under acidic conditions, which is higher than that of the pristine MoS 2 . The incorporation of SnS 2 into 2H-MoS 2 ultrathin sheets not only induces a phase but also can alter the local atomic arrangement, which in turn is verified by their magnetic response. The diamagnetic SnS 2 phase causes a decrease in symmetry and an increase in magnetic anisotropy of the Mo 3+ ions.

An effective Ru/CNT electrocatalyst plays a crucial role in solid-state lithium-carbon dioxide batteries. In the present article, ruthenium metal decorated on a multi-walled carbon nanotubes (CNTs) is introduced as a cathode for the lithium-carbon dioxide batteries with Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 solid-state electrolyte. The Ru/CNT cathode exhibits a large surface area, maximum discharge capacity, excellent reversibility, and long cycle life with low overpotential. The electrocatalyst achieves improved electrocatalytic performance for the carbon dioxide reduction reaction and carbon dioxide evolution reaction, which are related to the available active sites. Using the Ru/CNT cathode, the solid-state lithium-carbon dioxide battery exhibits a maximum discharge capacity of 4541 mA h g -1 and 45 cycles of battery life with a small voltage gap of 1.24 V compared to the CNT cathode (maximum discharge capacity of 1828 mA h g -1 , 25 cycles, and 1.64 V as voltage gap) at a current supply of 100 mA g -1 with a cutoff capacity of 500 mA h g -1 . Solid-state lithium-carbon dioxide batteries have shown promising potential applications for future energy storage.

Alkali metal-carbon dioxide (Li/Na-CO 2 ) batteries have generated widespread interest in the past few years owing to the attractive strategy of utilizing CO 2 while still delivering high specific energy densities. Among these systems, Na-CO 2 batteries are more cost effective than Li-CO 2 batteries because the former uses cheaper and abundant Na. Herein, a Ru/carbon nanotube (CNT) as a cathode material was used to compare the mechanisms, stabilities, overpotentials, and energy densities of Li-CO 2 and Na-CO 2 batteries. The potential of Na-CO 2 batteries as a viable energy storage technology was demonstrated.

The systematic substitution of Ba in the Sr site of Sr[Mg 2 Al 2 N 4 ]:Eu 2+ generates a deep-red-emitting phosphor with enhanced thermal luminescence properties. Gas pressure sintering (GPS) of all-nitride starting materials in Molybdenum (Mo) crucibles yields pure-phase red-orange-colored phosphors. Peaks in the synchrotron X-ray diffraction (SXRD) data show a systematic shift toward smaller angles due to the introduction of the larger Ba cation in the same crystal structure. The photoluminescence property reveals that Ba substitution shifts the original emission wavelength of Sr[Mg 2 Al 2 N 4 ]:Eu 2+ (625 nm) toward ∼690 nm for Ba[Mg 2 Al 2 N 4 ]:Eu 2+ . Thermal stability measurement of Sr 1- x Ba x [Mg 2 Al 2 N 4 ] indicates a systematic increase in stability from x = 0 to x = 1. X-ray absorption near-edge spectroscopy (XANES) results demonstrate the coexistence of Eu 2+ and Eu 3+ . The red-shift and the enhanced thermal stability reveals that the distance of the emitting 5 d level to the conduction band of Ba[Mg 2 Al 2 N 4 ]:Eu 2+ is large. The ionic size mismatch of Eu occupying a Ba site reduces the symmetry, thereby further splitting the degenerate emitting 5 d level and lowering the energy of the emitting center. The development of deep-red phosphors emitting at 670-690 nm ( x = 0.8-1.0) offers possible candidates for plant lighting applications.

Li-CO 2 batteries are of great interest among researchers due to their high energy density and utilization of the greenhouse gas CO 2 to produce energy. However, several shortcomings have been encountered in the practical applications of Li-CO 2 batteries, among which their poor cyclability and high charge overpotential necessary to decompose the highly insulating discharge product (Li 2 CO 3 ) are the most important. Herein, the spinel zinc cobalt oxide porous nanorods with carbon nanotubes (ZnCo 2 O 4 @CNTs) composite is employed as a cathode material in Li-CO 2 batteries to improve the latter's cycling performance. The ZnCo 2 O 4 @CNT cathode-based Li-CO 2 battery exhibited a full discharge capacity of 4275 mAh g -1 and excellent cycling performance over 200 cycles with a charge overpotential below 4.3 V when operated at a current density of 100 mA g -1 and fixed capacity of 500 mAh g -1 . The superior performance of the ZnCo 2 O 4 @CNT cathode composite was attributed to the synergistic effects of ZnCo 2 O 4 and CNT. The highly porous ZnCo 2 O 4 nanorod structures in the ZnCo 2 O 4 @CNT catalyst showed enhanced catalytic activity/stability, which effectively promoted CO 2 diffusion during the discharging process and accelerated Li 2 CO 3 decomposition at a low charge overpotential.

Cobalt sulfide (CoS x ) functioned as a co-catalyst to accelerate the kinetics of photogenerated electrons on Si photocathode, leading to the enhancement of solar hydrogen evolution efficiency. By doping phosphorus heteroatoms, CoS x materials showed an improved catalytic activity because of superior surface area and quantity of active sites. Furthermore, increased vacancies in unoccupied electronic states were observed, as more phosphorus atoms doped into CoS x co-catalysts. Although these vacant sites improved the capability to accept photoinduced electrons from Si photoabsorber, chemisorption energy of atomic hydrogen on catalysts was the dominant factor affecting in photoelectrochemical performance. We suggested that P-doped CoS x with appropriate doping quantities showed thermoneutral hydrogen adsorption. Excess phosphorus dopants in CoS x contributed to excessively strong adsorption with H atoms, causing the poor consecutive desorption ability of photocatalytic reaction. The optimal P-doped CoS x -decorated Si photocathode showed a photocurrent of -20.6 mA cm -2 at 0 V. Moreover, a TiO 2 thin film was deposited on the Si photocathode as a passivation layer for improving the durability. The current density of 10 nm TiO 2 -modified photocathode remained at approximately -13.3 mA cm -2 after 1 h of chronoamperometry.

The initiation of hydrogen energy production from sunlight through photoelectrochemical (PEC) system is an important strategy for resolving contemporary issues in energy requirement. Although precious Pt and other noble metals offer a desirable catalytic activity for this method, earth-abundant nonprecious metal catalysts must be developed for wide-scale application. In this regard, P-type silicon (P-Si) micropyramids (Si MPs) are a favorable photocathode because of their effective light-conversion properties and appropriate band gap position. In this study, we developed amorphous tungsten phosphosulfide nanosheets (WS 2- x P x NSs) on Si MPs through a simple thermal annealing process for solar-driven hydrogen evolution reaction. The P substitution in the nanostructure effectively produced many defective sites at the edges. The product exhibited an efficient photocurrent density of 19.11 mA cm -2 at 0 V and a low onset potential of 0.21 V RHE compared with tungsten disulfide (WS 2 ; 13.43 mA cm -2 ). The fabricated catalyst also showed desirable stability for up to 8 h for the WS 0.60 P 1.40 @Si MPs photocathode. The extraordinary activity could be due to numerous active sites provided by heteroatoms (sulfur and phosphorus) in the edges, resulting in dwindling reaction kinetics barrier and enhanced PEC activity.

An efficient H 2 evolution catalyst is developed by grafting CoSe 2 nanorods into C 3 N 4 nanosheets. The as-obtained C 3 N 4 -CoSe 2 heterostructure can show excellent performance in H 2 evolution with outstanding durability. To generate phatocathode for photoelectrochemical water splitting CoSe 2 grafted in C 3 N 4 was decorated on the top of p-Si microwires (MWs). p-Si/C 3 N 4 -CoSe 2 heterostructure can work as an efficient photocathode material for solar H 2 production in PEC water splitting. In 0.5 M H 2 SO 4 , p-Si/C 3 N 4 -CoSe 2 can afford photocurrent density -4.89 mA/cm 2 at "0" V vs RHE and it can efficiently work for 3.5 h under visible light. Superior activity of C 3 N 4 -CoSe 2 compared to CoSe 2 toward H 2 evolution is explained with the help of impedance spectroscopy.

This study employed silicon@cobalt dichalcogenide microwires (MWs) as wide range pH-tolerable photocathode material for solar water splitting. Silicon microwire arrays were fabricated through lithography and dry etching technologies. Si@Co(OH)2 MWs were utilized as precursors to synthesize Si@CoX2 (X = S or Se) photocathodes. Si@CoS2 and Si@CoSe2 MWs were subsequently prepared by thermal sulfidation and hydrothermal selenization reaction of Si@Co(OH)2, respectively. The CoX2 outer shell served as cocatalyst to accelerate the kinetics of photogenerated electrons from the underlying Si MWs and reduce the recombination. Moreover, the CoX2 layer completely deposited on the Si surface functioned as a passivation layer by decreasing the oxide formation on Si MWs during solar hydrogen evolution. Si@CoS2 photocathode showed a photocurrent density of -3.22 mA cm(-2) at 0 V (vs RHE) in 0.5 M sulfuric acid electrolyte, and Si@CoSe2 MWs revealed moderate photocurrent density of -2.55 mA cm(-2). However, Si@CoSe2 presented high charge transfer efficiency in neutral and alkaline electrolytes. Continuous chronoamperometry in acid, neutral, and alkaline solutions was conducted at 0 V (vs RHE) to evaluate the photoelectrochemical durability of Si@CoX2 MWs. Si@CoS2 electrode showed no photoresponse after the chronoamperometry test because it was etched through the electrolyte. By contrast, the photocurrent density of Si@CoSe2 MWs gradually increased to -5 mA cm(-2) after chronoamperometry characterization owing to the amorphous structure generation.

A successive preparation of FeCo2O4 nanoflakes arrays on nickel foam substrates is achieved by a simple hydrothermal synthesis method. After 170 cycles, a high capacity of 905 mAh g(-1) at 200 mA g(-1) current density and very good rate capabilities are obtained for lithium-ion battery because of the 2D porous structures of the nanoflakes arrays. The distinctive structural features provide the battery with excellent electrochemical performance. The symmetric supercapacitor on nonaqueous electrolyte demonstrates high specific capacitance of 433 F g(-1) at 0.1 A g(-1) and 16.7 F g(-1) at high scan rate of 5 V s(-1) and excellent cyclic performance of 2500 cycles of charge-discharge cycling at 2 A g(-1) current density, revealing excellent long-term cyclability of the electrode even under rapid charge-discharge conditions.

The orange-red emitting phosphors based on M(2)Si(5)N(8):Eu (M = Sr, Ba) are widely utilized in white light-emitting diodes (WLEDs) because of their improvement of the color rendering index (CRI), which is brilliant for warm white light emission. Nitride-based phosphors are adopted in high-performance applications because of their excellent thermal and chemical stabilities. A series of nitridosilicate phosphor compounds, M(2-x)Si(5)N(8):Eu(x) (M = Sr, Ba), were prepared by solid-state reaction. The thermal degradation in air was only observed in Sr(2-x)Si(5)N(8):Eu(x) with x = 0.10, but it did not appear in Sr(2-x)Si(5)N(8):Eu(x) with x = 0.02 and Ba analogue with x = 0.10. This is an unprecedented investigation to study this phenomenon in the stable nitrides. The crystal structural variation upon heating treatment of these compounds was carried out using the in situ XRD measurements. The valence of Eu ions in these compounds was determined by electron spectroscopy for chemical analysis (ESCA) and X-ray absorption near-edge structure (XANES) spectroscopy. The morphology of these materials was examined by transmission electron microscopy (TEM). Combining all results, it is concluded that the origin of the thermal degradation in Sr(2-x)Si(5)N(8):Eu(x) with x = 0.10 is due to the formation of an amorphous layer on the surface of the nitride phosphor grain during oxidative heating treatment, which results in the oxidation of Eu ions from divalent to trivalent. This study provides a new perspective for the impact of the degradation problem as a consequence of heating processes in luminescent materials.

Instead of developing a novel red phosphor individually, this work proposes the production of white light by combining a near-ultraviolet/ultraviolet diode chip with blue and special yellow phosphors: the yellow phosphor includes the red and green components with high color saturation. The availability of this scheme is demonstrated by preparing a white light-emitting diode (WLED) with color rendering index (Ra) up to 90.3. The desired single-mass yellow phosphor is successfully screened out from the YVO(4):Bi(3+),Eu(3+) system by using a combinatorial chemistry approach. When the emission color and luminous efficiency are both considered, the best composition for producing white light is (Y(1-s-t)Bi(s)Eu(t))VO(4) with 0.040 < or = s < or = 0.050 and 0 < t < or = 0.015. The red component that is required for a high-Ra WLED is obtained through sensitizing luminescence of Eu(3+) by Bi(3+) in a YVO(4) host; meanwhile, both Bi(3+) and Eu(3+) emission are improved by keeping the Bi(3+) and Eu(3+) contents close to the critical concentration.

This investigation demonstrates the magnetic properties and nanostructures of CoPt(3) wire arrays that were fabricated by electrodeposition using a porous alumina template. The X-ray absorption analysis clearly verified the occurrence of a phase transition in CoPt(3) nanowires. This phase transition significantly influences the magnetic properties and enhances coercivity and squareness. The phase transition of CoPt(3) nanowires was from a random alloy distribution to anisotropically ordered CoPt(3) (L1(2)). The thermally induced phase transition of CoPt(3) nanowires to ordered L1(2) CoPt(3) through a "cluster-in-cluster" intermediate state via interdiffusion processes is revealed. The mechanism exhibited by these CoPt(3) nanowires is proposed to explain the strong correlation between their magnetic character and their atomic distribution.

This investigation describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters. The galvanic replacement reaction between silver and chloroauric acid was adopted to prepare hollow metal nanoparticles. This approach is extended to produce nanorattles of Au cores and Au shells by starting with Au(core)Ag(shell) nanoparticles as templates. The effect of temperature on the nanostructure of the final product is also considered. The composition of the shell in nanorattles can be controlled by varying the reaction temperature (to form pure gold or gold-silver alloy, for example). X-ray absorption fine structure spectroscopy is conducted to elucidate the fine structure of these nanoparticles. Partial alloying between the Au core and the Ag shell is observed by extended X-ray absorption fine structure (EXAFS).