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C 2 products are more desirable than C 1 products during CO 2 electroreduction (CO 2 ER) because the former possess higher energy density and greater industrial value. For CO 2 ER, Cu is a well-known catalyst, but the selectivity toward C 2 products is still a big challenge for researchers due to complex intermediates, different final products, and large space of the catalyst due to its morphology, plane, size, host surface etc. Using density functional theory (DFT) calculations, we find that alloying of Cu nanoparticles can help to enhance the selectivity toward C 2 products during CO 2 ER with a low overpotential. By a systematic investigation of 111 planes (which prefer the C 1 product in the case of bulk Cu), the alloys show the generation of C 2 products via *CO-*CO dimerization (* indicates adsorbed state). It also suppresses the counter-pathway of hydrogenation of *CO to *CHO, which leads to C 1 products. Further, we find that *CH 2 CHO is the bifurcating intermediate to distinguish between ethanol and ethylene as the final product. We have used simple graphical construction to identify the catalyst for CO 2 ER over HER, and vice versa. We have also defined the case of hydrogen poisoning and projected a parity plot to recognize the catalyst for C 2 product evolution over the C 1 product. Our study reveals that Cu-Ag and Cu-Zn catalysts selectively promote ethanol production on 111 planes. Moreover, an edge-doped 2SO 2 graphene nanoribbon as the host layer further lowers the barrier and selectively promotes ethanol on Cu 38 - and Cu 79 -based alloys. This work provides new theoretical insights into designing Cu-based nanoalloy catalysts for C 2 product formation on the 111 plane.

Defect engineering through modification of their surface linkage is found to be an effective pathway to escalate the solar energy conversion efficiency of metal-organic frameworks (MOFs). Herein, defect engineering using controlled decarboxylation on the NH 2 -UiO-66 surface and integration of ultrathin NiCo-LDH nanosheets synergizes the hydrogen evolution reaction (HER) under a broad visible light regime. Diversified analytical methods including positron annihilation lifetime spectroscopy were employed to investigate the role of Zr 3+ -rich defects by analyzing the annihilation characteristics of positrons in NH 2 -UiO-66, which provides a deep insight into the effects of structural defects on the electronic properties. The progressively tuned photophysical properties of the NiCo-LDH@NH 2 -UiO-66-D-heterostructured nanocatalyst led to an impressive rate of HER (∼2458 μmol h -1 g -1 ), with an apparent quantum yield of ∼6.02%. The ultrathin NiCo-LDH nanosheet structure was found to be highly favored toward electrostatic self-assembly in the heterostructure for efficient charge separation. Coordination of Zr 3+ on the surface of the NiCo-LDH nanosheet support through NH 2 -UiO-66 was confirmed by X-ray absorption spectroscopy and electron paramagnetic resonance spectroscopy techniques. Femtosecond transient absorption spectroscopy studies unveiled a photoexcited charge migration process from MOF to NiCo-LDH which favorably occurred on a picosecond time scale to boost the catalytic activity of the composite system. Furthermore, the experimental finding and HER activity are validated by density functional theory studies and evaluation of the free energy pathway which reveals the strong hydrogen binding over the surface and infers the anchoring effect of the ultrathin layered double hydroxide (LDH) in the vicinity of the Zr cluster with a strong host-guest interaction. This work provided a novel insight into efficient photocatalysis via defect engineering at the linker modulation in MOFs.

This work showcases a novel strategy for the synthesis of shape-dependent alloy nanostructures with the incorporation of solid substrates, leading to remarkable enhancements in the electrocatalytic performance. Herein, an aqueous medium approach has been used to synthesize an octahedral Pd X Cu Y alloy of different Pd:Cu ratios to better comprehend their electrocatalytic potential. With the aim to outperform high activity and efficient stability, zirconium oxide (ZrO 2 ), graphene oxide nanosheets (GONs), and hexagonal boron nitride nanosheets (hBNNs) solid substrates are occupied to decorate the optimized Pd 3 Cu 7 catalyst with a minimum 5 wt % metal loading. When compared to the counterparts and different ratios, the Pd 3 Cu 7 @hBNNs catalyst exhibited an optimal activity for hydrogen evolution reaction (HER). The lower overpotential and Tafel values observed are 64 and 51 mV/dec for Pd 3 Cu 7 @hBNNs followed by Pd 3 Cu 7 @ZrO 2 , which showed a 171 mV overpotential and a 98 mV/dec Tafel value, respectively. Meanwhile, the Pd 3 Cu 7 @GONs were found to have a 202 mV overpotential and a 110 mV/dec Tafel value. The density functional theory, which achieves a lower free energy (Δ G H* ) value for Pd 3 Cu 7 @hBNNs than the other catalysts for HER, further supports its excellent performance in achieving the Volmer-Heyrovsky mechanism path. Moreover, the superior HER activity and sturdier resilience after 8 h of stability may be due to the synergy between the metal atoms, monodisperse decoration, and the coordination effect of the support material.

The main challenges impeding the widespread use of organic-inorganic lead halide perovskites in modern-day technological devices are their long-term instability and lead contamination. Among other environmentally convivial and sustainable alternatives, Cs 2 SnX 6 (X = Cl, Br, and I) compounds have shown promise as ambient-stable, lead-free materials for energy harvesting, and optoelectronic applications. Additionally, they have demonstrated tremendous potential for the fabrication of self-powered nanogenerators in conjunction with piezoelectric polymers like polyvinylidene-fluoride (PVDF). We report on the fabrication of composites constituting solvothermally synthesized Cs 2 SnX 6 nanostructures and PVDF. The electroactive phases in PVDF were boosted by the incorporation of Cs 2 SnX 6 , leading to enhanced piezoelectricity in the composites. First-principles density functional theory (DFT) studies were carried out to understand the interfacial interaction between the Cs 2 SnX 6 and PVDF, which unravels the mechanism of physisorption between the perovskite and PVDF, leading to enhanced piezoresponse. The halide ions in the inorganic Cs 2 SnX 6 perovskites were varied systematically, and the piezoelectric behaviors of the respective piezoelectric nanogenerators (PENGs) were investigated. Further, the dielectric properties of these halide perovskite-based hybrids are quantified, and their piezoresponse amplitude, piezoelectric output signals, and charging capacity are also evaluated. Out of the several films fabricated, the optimized Cs 2 SnI 6 _PVDF film shows a piezoelectric coefficient ( d 33 ) value of ∼200 pm V -1 and a remanent polarization of ∼0.74 μC cm -2 estimated from piezoresponse force microscopy and polarization hysteresis loop measurement, respectively. The optimized Cs 2 SnI 6 _PVDF-based device produced an instantaneous output voltage of ∼167 V, a current of ∼5.0 μA, and a power of ∼835 μW across a 5 MΩ resistor when subjected to periodic vertical compression. The output voltage of this device is used to charge a capacitor with a 10 μF capacitance up to 2.2 V, which is then used to power some commercial LEDs. In addition to being used as a pressure sensor, the device is employed to monitor human physiological activities. The device demonstrates excellent operational durability over a span of several months in an ambient environment vouching for its exceptional potential in application to mechanical energy harvesting and pressure sensing applications.

The excess anthropogenic CO 2 depletion via the catalytic approach to produce valuable chemicals is an industrially challenging, demanding, and encouraging strategy for CO 2 fixation. Herein, we demonstrate a selective one-pot strategy for CO 2 fixation into "oxazolidinone" by employing stable porous trimetallic oxide foam (PTOF) as a new catalyst. The PTOF catalyst was synthesized by a solution combustion method using transition metals Cu, Co, and Ni and systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), N 2 sorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS) analysis. Due to the distinctive synthesis method and unique combination of metal oxides and their percentage, the PTOF catalyst displayed highly interconnected porous channels along with uniformly distributed active sites on its surface. Well ahead, the PTOF catalyst was screened for the fixation of CO 2 into oxazolidinone. The screened and optimized reaction parameters revealed that the PTOF catalyst showed highly efficient and selective activity with 100% conversion of aniline along with 96% selectivity and yield toward the oxazolidinone product at mild and solvent-free reaction conditions. The superiority of the catalytic performance could be due to the presence of surface active sites and acid-base cooperative synergistic properties of the mixed metal oxides. A doubly synergistic plausible reaction mechanism was proposed for the oxazolidinone synthesis experimentally with the support of DFT calculations along with bond lengths, bond angles, and binding energies. In addition, stepwise intermediate formations with the free energy profile were also proposed. Also, the PTOF catalyst displayed good tolerance toward substituted aromatic amines and terminal epoxides for the fixation of CO 2 into oxazolidinones. Very interestingly, the PTOF catalyst could be significantly reused for up to 15 consecutive cycles with stable activity and retention in physicochemical properties.

Visible light-mediated photoredox catalysis has emerged to be a fascinating approach for the activation of CO 2 and its subsequent fixation into valuable chemicals utilizing renewable and inexhaustible solar energy. Although great progress has been made in CO 2 photoreduction, visible light-assisted organic synthesis using CO 2 as a reactive substrate is rarely explored. Herein, we report an efficient, facile, and economically viable photoredox-mediated approach for the synthesis of important β-thioacids via carboxylation of olefins with CO 2 and thiols over a porous functionalized metal-organic framework (MOF), Fe-MIL-101-NH 2 , as a photocatalyst under ambient conditions. This multicomponent reaction offers wide substrate scope, mild reaction conditions, easy work-up, cost-effective and reusable photocatalysts, and higher product selectivity. Computational studies suggested that CO 2 interacts with the thiophenol-styrene adduct to facilitate the synthesis of β-thioacids in almost quantitative yields.

As a promising candidate for low-cost and eco-friendly thin-film photovoltaics, the emerging quaternary chalcogenide based solar cells have experienced rapid advances over the past decade. Here, we propose quaternary semiconducting chalcogenides CuZn 2 AlSe 4 (CZASe) through cross-substitutions (cation mutations). The nonexistence of imaginary modes in the entire Brillouin zone of CZASe represents the inherent dynamic stability of the system. The electronic, optical, and defect properties of stannite CZASe quaternary semiconducting material was systematically investigated using density functional theory calculations. We have found that the chemical-potential control is very important for growing good-quality crystals and also to avoid secondary-phase formations such as ZnSe, Al 2 ZnSe 4 , and Cu 3 Se 2 . The observed p-type conductivity is mainly due to antisite defect Cu Zn , which has the lowest formation energy with a relatively deeper acceptor level than that of the Cu vacant site (V Cu ). The electronic band structures of vacancies and antisite defects by means of hybrid functional calculations show energy band shifting and energy band narrowing or broadening, which eventually tunes the optical band gap and improves the solar energy-conversion performance of semiconducting CZASe. Our results suggest that the stannite CZASe quaternary chalcogenides could be promising candidates for the efficient earth-abundant thin-film solar cells., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Using the first-principles approach, we investigated the electronic and chemical properties of wurtzite silicon carbide (2H-SiC) monolayer and thin film structures and substantiated their catalytic activity toward CO oxidation. 2H-SiC monolayer, being planar, is quite stable and has moderate binding with O2, while CO interacts physically; thus, the Eley-Rideal (ER) mechanism prevails over the Langmuir-Hinshelwood (LH) mechanism with an easily cleared activation barrier. Contrarily, 2H-SiC thin film, which exhibits a nonplanar structure, allows moderate binding of both CO and O2 on its surface, thus favoring the LH mechanism over the ER one. Comprehending these results leads to a better understanding of the reaction mechanisms involving structural contrast. Weak overlapping between the 2p(z)(C) and 3p(z)(Si) orbitals of the SiC monolayer system has been found to be the primary reason to revert the active site toward sp(3) hybridization, during interaction with the molecules. In addition, the influences of graphite and Ag(111) substrates on the CO oxidation mechanism were also studied, and it is observed that the ER mechanism is preserved on SiC/G system, while CO oxidation on the SiC/Ag(111) system follows the LH mechanism. The calculated Sabatier activities of the SiC catalysts show that the catalysts are very efficient in catalyzing CO oxidation.

A scalable and controllable nanoscale perforation method for graphene is developed on the basis of the two-step thermal activation of a graphene aerogel. Different resistance to the thermal oxidation between graphitic and defective domains in the weakly reduced graphene oxide is exploited for the self-limiting nanoscale perforation in the graphene basal plane via selective thermal degradation of the defective domains. The resultant nanoporous graphene with a narrow pore-size distribution addresses the long-standing challenge for the high-level doping of graphene with lattice-mismatched large-size heteroatoms (S and P). Noticeably, this novel heteroatom doping strategy is demonstrated to be highly effective for oxygen reduction reaction (ORR) catalysis. Not only the higher level of heteroatom doping but also favorable spin and charge redistribution around the pore edges leads to a strong ORR activity as supported by density functional theory calculations.

We investigated the microscopic mechanism of ion transport in iodide ionic liquid, using first-principles calculations. We show that the desorption barrier of polyiodides (I3(-) or I5(-)) from the cation is in a similar energy range as or higher than the barrier for the bond dissociation and ensued desorption of neutral iodine (I2). This suggests that, instead of the physical diffusion of such a negatively charged multiatomic species, the exchange of neutral iodine (I2) between the polyiodides can be an easier channel for the movement of polyiodide. For the transport of the monoiodide anion (I(-)), we suggest the contribution of the Grotthuss-type ion exchange through the intermediately formed even-member anion (I2n(-)), in addition to drift and diffusion. As a result, we suggest that, instead of the commonly cited diffusion of the triiodide/iodide (I3(-)/I(-)) redox couple, the exchange of neutral iodine (I2) and the Grotthuss-type transport (I(-)) constitute the dominant ion transport mechanism.