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While attention is focused on Li–CO2 batteries due to their high energy density and ability to utilize carbon, their detailed cathodic reaction mechanism remains unclear. Thus far, the recognized reaction formula involves CO2 reduction with carbon as the reduced product (3CO2 + 4Li+ + 4e− → 2Li2CO3 + C, E° = 2.8 V vs. Li+/Li). However, evidence of carbon formation is seldom provided in previous studies. The potential of the potential-determining step (CO2 + e− → CO2−, E° = 1.1 V vs. Li+/Li) in the reaction is much lower than the common working potential (2.6 V). Furthermore, the calculated redox potential at 2.8 V itself is incorrect since the calculation includes chemical reaction(s) that does not involve electron transfer. These findings do not suggest that the proposed cell reaction is correct. Herein, we propose that the previously observed reaction is caused by O2 and H2O participating in the electrochemical reaction to give such a high working potential. The formation of Li2CO3 as the only discharge product can support our statement through examination by soft X-ray absorption spectroscopy. Moreover, we find that the reaction of sole CO2 reduction can only happen at a low potential of 1.1 V with a current density of 100 mA g−1. CO, rather than C, is found to be the discharge product. Thus, both O2 and H2O contamination should be considered when studying Li–CO2 batteries, and the discharge product should be characterized carefully to claim the reaction formula. [ABSTRACT FROM AUTHOR]

Limiting the carbon emission to the atmosphere requires the efficient utilization of carbonaceous gases and their capture via well‐designed platforms. Metal–CO2 batteries are currently being demonstrated as the route to utilize CO2 and produce energy simultaneously. In particular, Na–CO2 batteries are considered an alternative to Li‐batteries because of their abundance and low cost. In the current review, the developments in the field of Na–CO2 batteries are discussed. Carbon dioxide reactions to the decomposition of discharge products have been discussed elaborately. The main discharge products of Na–CO2 batteries are Na2CO3 and C. In the current review, various strategies are discussed to decompose the discharge products and hence improve cycle stability. The fraction of CO2 has a substantial influence on cell cycles. A plausible route of battery reaction can be drawn with the help of an ex situ analysis of the electrodes. The final part of the review focuses on the use of solid‐state Na‐ion conductors in Na–CO2 batteries. [ABSTRACT FROM AUTHOR]

The generation of clean energy is necessary for future technological developments. The utilization of solar illumination to produce H2 from water electrolysis is an alternative route to address the issue. However, the reaction is a thermodynamically uphill task. Furthermore, designing a photocathode, which can use most of the incident radiation for the photoelectrochemical (PEC) reaction, plays an important role. Surface-modified p-Si can be an economically viable option. The sluggish electro-kinetics on the Si surface has been rectified with coatings of cocatalyst materials. In the current review, we have discussed the possible modifications performed on the p-Si surface to reduce the loss due to reflection and coating of the cocatalyst, e.g. MoS2 on p-Si to improve H2 evolution. The facile charge carrier kinetics at the electrode–electrolyte interface has also been discussed. The development of cocatalysts has been focused on our previous experience for two decades. From surface plasmon resonance to heteroatom doping, that is, intentional defect formation and heterostructure design, we have included a comprehensive discussion on cocatalysts. The energetics of single atom replacement and its implications for efficiency has been included. This review gives insights into the currently emerging cocatalyst design for PEC water splitting. In this regard, the review presents insights into the phase transformation in MoS2 during the PEC process using operando techniques. A discussion on the effect of single atom replacement in the inactive basal-MoS2 plane has been included. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) phosphors have gained a substantial amount of attention in the past few years simply due to their numerous applications. Recent publications have reported interesting findings regarding the fundamentals of phosphors. However, the unclear application of these phosphors limits their potential. This mini review aims to provide insights for researchers regarding the potential applications of NIR phosphors and their perspectives for further development of NIR phosphor technology. [ABSTRACT FROM AUTHOR]

Rechargeable Na–CO2 batteries are promising energy storage devices as they not only provide high energy density but also utilize earth-abundant Na and the greenhouse gas CO2. However, Na–CO2 battery development is deterred due to the sluggish electrochemical reactions at the cathode. The cathode catalyst is unable to decompose the insulating discharge product Na2CO3, thereby leading to increasing charge overpotential and poor cycle performance of the Na–CO2 battery. Herein, we report spinel ZnCo2O4 porous nanorods with multiwall carbon nanotubes (ZnCo2O4@CNT) as a cathode composite in the Na–CO2 batteries to effectively decompose Na2CO3 and improve the cycle performance. The battery shows stable discharge–charge for at least 150 cycles with a limited capacity of 500 mA h g−1 at 100 mA g−1. Moreover, the battery with the ZnCo2O4@CNT cathode catalyst exhibits a reversible discharge–charge capacity of 12 475 mA h g−1. Theoretical simulations suggest that the adsorption energies of CO2, Na, and Na2CO3 on the three surfaces of ZnCo2O4 are favorable for the CO2RR and CO2ER during the charge–discharge of the Na–CO2 battery. The surfaces of ZnCo2O4 investigated for catalytic activity include the [001] surface, the [111] surface with only exposed Co atoms, and the [111] surface with exposed Co and Zn atoms. The density of states calculation results further reveal that Co atoms on these three surfaces are possibly the catalytic active sites for the CO2RR and CO2ER during the charge–discharge of the Na–CO2 battery. [ABSTRACT FROM AUTHOR]

Phosphor-converted light-emitting diodes (LEDs) have recently become a promising candidate for next-generation devices used in agriculture and horticulture. In principle, they can overcome the limitations of regular daily sunshine. Here, the principle of LED-promoted plant growth was demonstrated by using the Ga2O3:Cr3+ phosphor with an extremely high quantum yield of 92.4%. The detailed structural and luminescent properties were characterized using X-ray diffraction, temperature-dependent photoluminescence, and pressure-dependent photoluminescence. The results reveal the unique two electronic spin-forbidden transition emissions (R1 and R2) of the Ga2O3:Cr3+ phosphor. Plant growth experiments were also conducted to evaluate the practical applications of the as-prepared phosphors, showing that they exhibit obvious positive effects on plants. This work reveals the important role of LEDs in agriculture and horticulture, as well as their potential practical applications. [ABSTRACT FROM AUTHOR]

Li–air batteries are limited to lab‐scale research owing to the uninterrupted formation of discharge products. In the case of Li–CO2 batteries, the increase in overpotential caused by Li2CO3 formation results in cell death. In this study, Cu2O crystals having three different types of shapes (i.e., cubic, octahedral, and rhombic) were synthesized to compare their catalytic activity toward CO2 reactions. The full‐cycle and long‐term stability test revealed that rhombohedral Cu2O facilitates Li2CO3 decomposition more efficiently than that of cubic and octahedral Cu2O. The cycle was extended to investigate the photocatalytic activity of the rhombic Cu2O by illuminating the cell. The repeated cycles to 1 h showed a maximum overpotential of 1.5 V, which is 0.5 V lower than that of the cell without illumination. A postmortem analysis of the cell after dividing the cycles into segments demonstrated interesting results concerning the role of light and Cu2O during the cell cycle. [ABSTRACT FROM AUTHOR]

Lithium-ion (Li+) batteries suffer from problems caused by the chemical instability of their organic electrolytes. Solid-state electrolytes that exhibit high ionic conductivities and are stable to lithium metal are potential replacements for flammable organic electrolytes. Garnet-type Li7La3Zr2O12 is a promising solid-state electrolyte for next-generation solid-state Li batteries. In this study, we prepared mono-, dual-, and ternary-doped lithium (Li) garnets by doping tantalum (Ta), tantalum–barium (Ta–Ba), and tantalum–barium–gallium (Ta–Ba–Ga) ions, along with an undoped Li7La3Zr2O12 (LLZO) cubic garnet electrolyte, using a conventional solid-state reaction method. The effect of multi-ion doping on the Li+ dynamics in the garnet-type LLZO was studied by combining joint Rietveld refinement against X-ray diffraction and high-resolution neutron powder diffraction analyses with the results of Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and multinuclear magic angle spinning nuclear magnetic resonance. Our results revealed that Li+ occupancy in the tetrahedrally coordinated site (24d) increased with increased multi-ion doping in LLZO, whereas Li+ occupancy in the octahedrally coordinated site (96h) remained constant. Among the investigated compounds, the ternary-doped garnet structure Li6.65Ga0.05La2.95Ba0.05Zr1.75Ta0.25O12 (LGLBZTO) exhibited the highest total ionic conductivity of 0.72 and 1.24 mS cm−1 at room temperature and 60 °C, respectively. Overall, our findings revealed that the dense microstructure and increased Li+ occupancy in the tetrahedral-24dLi1 site played a key role in achieving the maximum room-temperature Li-ion conductivity in the ternary-doped LGLBZTO garnet, and that the prepared ternary-doped LGLBZTO was a potential solid electrolyte for Li-ion batteries without polymer adhesion. [ABSTRACT FROM AUTHOR]