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Herein, metal indium sulfides (ZnIn2S4, NiIn2S4, and CuInS2) were synthesized using a hydrothermal method. Nanosheet-assembled microspheres were observed. According to cyclic voltammetry, CuInS2revealed 19 and 6-fold current density enhancement compared to ZnIn2S4and NiIn2S4, respectively. Also, linear sweep voltammetry results suggested a higher current density of CuInS2than the others. The lowest Tafel plot of CuInS2(189.15 mV dec−1) suggested the improvement of electrocatalytic activity compared to those of ZnIn2S4(282.53 mV dec−1) and NiIn2S4(247.32 mV dec−1). An H-type cell was used for selective electrochemical reduction of CO2into CH4. The gaseous and liquid products were analyzed by gas chromatography and 1H NMR, respectively. A higher Faraday efficiency (FE) was observed in CuInS2(80.11%) compared to those in ZnIn2S4(67.78%) and NiIn2S4(75.31%) towards the electrocatalytic reduction of CO2into methane (CH4) at −0.6 V vs.RHE. A higher turnover frequency (TOF) value was observed in CuInS2compared to those in the other catalysts. CuInS2demonstrated remarkable stability, with neither an obvious current drop nor large FE fluctuation for 20 h during electrochemical CO2reduction into CH4, indicating a superior electrocatalytic performance. The higher electrochemical performance of CuInS2is associated with a larger BET surface area/electrochemical surface area, rich structural design, and abundant active sites. This work indicates a promising strategy for developing a ternary electrocatalyst for highly selective electrochemical reduction of CO2to CH4.

We report the intercalation of polyacrylonitrile nanoparticles in Ti3C2TxMXene layers through simple sonication. The use of polyacrylonitrile, which was synthesized via radical polymerization, offered dual benefits: (1) It increased the interlayer spacing of MXene, thereby exposing more surface area and enhancing ion transport channels during charge and discharge cycles, and (2) Integrating MXene with polyacrylonitrile enables the creation of a composite with conductive properties, following percolation principle. X-ray diffraction analysis showed an increase in the c-lattice parameter, indicative of the interlayer spacing, from 22.31 Å for the pristine MXene to 37.73 Å for the MXene–polyacrylonitrile composite. The intercalated polyacrylonitrile nanoparticles facilitated the delamination by weakening the interlayer interactions, especially during sonication. Electrochemical assessments revealed significant improvement in the properties of the MXene–polyacrylonitrile composite compared to the pristine MXene. The assembled asymmetric device achieved a good specific capacitance of 32.1 F/g, an energy density of 11.42 W h/kg, and 82.2% capacitance retention after 10,000 cycles, highlighting the practical potential of the MXene–polyacrylonitrile composite.

The carbon cycle, by which carbon atoms circulate between atmosphere, oceans, lithosphere, and the biosphere of Earth, is a current hot research topic. The carbon cycle occurring in the lithosphere (e.g., sedimentary carbonates) is based on weathering and metamorphic events so that its processes are considered to occur on the geological time scale (i.e., over millions of years). In contrast, we have recently reported that carbonate anions intercalated within a hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125·yH2O), a class of a layered double hydroxide (LDH), are dynamically exchanging on time scale of hours with atmospheric CO2under ambient conditions. (Ishihara et al., J. Am. Chem. Soc.2013, 135, 18040–18043). The use of 13C-labeling enabled monitoring by infrared spectroscopy of the dynamic exchange between the initially intercalated 13C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. In this article, we report the significant influence of Mg/Al ratio of LDH on the carbonate anion exchange dynamics. Of three LDHs of various Mg/Al ratios of 2, 3, or 4, magnesium-rich LDH (i.e., Mg/Al ratio = 4) underwent extremely rapid exchange of carbonate anions, and most of the initially intercalated carbonate anions were replaced with carbonate anions derived from atmospheric CO2within 30 min. Detailed investigations by using infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, elemental analysis, adsorption, thermogravimetric analysis, and solid-state NMR revealed that magnesium rich LDH has chemical and structural features that promote the exchange of carbonate anions. Our results indicate that the unique interactions between LDH and CO2can be optimized simply by varying the chemical composition of LDH, implying that LDH is a promising material for CO2storage and/or separation.

Platinum-decorated mesoporous TiO2is synthesized by the self-assembly of polymeric micelles of an asymmetric triblock copolymer with three chemically distinct units in an acidic tetrahydrofuran solution. The strong hydrophobic interaction of platinum(II) 2,4-pentanedionate with a polystyrene core and electrostatic interaction of titanium tetraisopropoxide with a poly(vinylpyridine) shell enable us to directly synthesize crystalline mesoporous TiO2with platinum nanoparticles. A thermally stable block copolymer prevents collapse of the ordered mesostructure during the calcination process. The platinum source is in situ reduced to form the platinum nanoparticles on the TiO2walls. The sensing performance of platinum-decorated mesoporous TiO2is studied in detail using a quartz crystal microbalance technique, and it is found that it shows excellent sensitivity for acetaldehyde.

Recently, monolayer or few‐layered phosphorene nanosheets and other phosphorene‐based materials have gained huge attention due to their unique semiconducting and optical properties. But there is a huge unexplored area of research where phosphorene‐based catalysts could find new applications. Among these are the urgency of making new functionalized phosphorene materials and studying their catalytic (including photo and electrocatalytic) activities in various types of reactions. Phosphorene has a wide range of emerging applications in the field of energy conversion and storage, photovoltaic devices, and biomedical applications. However, the application of 2D phosphorene‐based catalyst in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), reduction of CO2into green fuels, and the nitrogen electroreduction reaction (N2RR) have not been explored further. Herein, state‐of‐the‐art synthetic strategies of 2D phosphorene produced from allotropes of black phosphorus with their significant role as nanocatalysts in the HER, OER, hydrogen storage, electrochemical reduction of CO2into valuable green fuels, and the N2RR are focused on. This review provides a wide range of knowledge on the current scenario to the researcher, scientist, industrialist, and professional working in the field of material research for energy applications. Black phosphorous and phosphorene‐based materials are an emerging field of research due to unique semi‐conducting and optical properties. The review focuses on state‐of‐the‐art synthetic strategies of 2D phosphorene‐based catalysts in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), hydrogen storage, electrochemical reduction of CO2into valuable green fuels, and nitrogen electroreduction reaction (N2RR).