Banerjee, Amitava

Electrochemical urea synthesis is a promising technology for carbon utilization. Herein, we report a CoPc-MoS2 system for promoting urea synthesis by a C-N coupling reaction. Dual metal sites mediate N2 activation and CO2 adsorption insertion to produce a urea yield of 175.6 μg h−1 mgcat−1 at −0.7 V vs. RHE.

A primary concern towards achieving a robust and sustainable water-splitting strategy consists in the development and designing of non-precious hydrogen evolution electrocatalysts capable of operating at relatively high current densities. In the present density functional theory (DFT) based study, we explored and identified α-NbB2-based catalysts consisting of Borophene as graphene-like noble metal-free networks in Niobium-metal based networks, as promising catalysts for the hydrogen-evolution reaction (HER). Our results unveiled that Fe/Co covalent doping in α-NbB2 {001} surface provides high-efficiency HER activity sites, namely, TNb-sites in Nb-terminated Fe/Co-NbB2 {001} surface with the lowest ΔGH∗ Gibbs free energy value of about 0.264/0.278 eV, which further drops to a very optimal value in the range of ΔGH∗ ≤ ± 0.10 eV upon the implementation of an external electric field. Furthermore, it was also revealed that in contrast to the extensively used Pt-based surface catalysts, both α-NbB2 and Fe/Co-NbB2 catalysts can sustain consistently high catalytic activity for HER over a very large hydrogen coverage and thus ensure a large density of effective catalytic free sites.

Lithium-ion batteries continue to be a critical part of the search for enhanced energy storage solutions. Understanding the stability of interfaces (surfaces and grain boundaries) is one of the most crucial aspects of cathode design to improve the capacity and cyclability of batteries. Interfacial engineering through chemical modification offers the opportunity to create metastable states in the cathodes to inhibit common degradation mechanisms. Here, we demonstrate how atomistic simulations can effectively evaluate dopant interfacial segregation trends and be an effective predictive tool for cathode design despite the intrinsic approximations. We computationally studied two surfaces, {001} and {104}, and grain boundaries, ς3 and ς5, of LiCoO2 to investigate the segregation potential and stabilization effect of dopants. Isovalent and aliovalent dopants (Mg2+, Ca2+, Sr2+, Sc3+, Y3+, Gd3+, La3+, Al3+, Ti4+, Sn4+, Zr4+, V5+) were studied by replacing the Co3+ sites in all four of the constructed interfaces. The segregation energies of the dopants increased with the ionic radius of the dopant. They exhibited a linear dependence on the ionic size for divalent, trivalent, and quadrivalent dopants for surfaces and grain boundaries. The magnitude of the segregation potential also depended on the surface chemistry and grain boundary structure, showing higher segregation energies for the ς5 grain boundary compared with the lower energy ς3 boundary and higher for the {104} surface compared to the {001}. Lanthanum-doped nanoparticles were synthesized and imaged with scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) to validate the computational results, revealing the predicted lanthanum enrichment at grain boundaries and both the {001} and the {104} surfaces.

The successful deployment of technologies for the electrocatalytic nitrogen reduction reaction (e-NRR) to synthesize ammonia would enable distributed ammonia production with lower greenhouse gas emissions compared to the Haber-Bosch process. However, electrocatalysts that can readily activate N2, promote selective ammonia formation over the competing hydrogen evolution reaction, and maintain stability under reaction conditions are needed to enable this technology. Herein, we give our perspective on metal oxynitrides (AxByOwNz) as an emerging and underexplored materials class for e-NRR. We contrast the activity, selectivity, and stability of metal oxynitrides with those of their metal nitride and metal oxide counterparts. We discuss the different possible e-NRR reaction mechanisms on metal oxynitrides, emphasize challenges related to using metal oxynitrides for e-NRR, and provide an outlook for future research. Ultimately, the huge design space of metal oxynitrides is ripe for exploration to find catalyst formulations that overcome some of the limitations of traditional metal oxides and metal nitrides for e-NRR.

Point defect formation and migration in oxides governs a wide range of phenomena from corrosion kinetics and radiation damage evolution to electronic properties. In this study, we examine the thermodynamics and kinetics of anion and cation point defects using density functional theory in hematite ( α -Fe2O3), an important iron oxide highly relevant in both corrosion of steels and water-splitting applications. These calculations indicate that the migration barriers for point defects can vary significantly with charge state, particularly for cation interstitials. Additionally, we find multiple possible migration pathways for many of the point defects in this material, related to the low symmetry of the corundum crystal structure. The possible percolation paths are examined, using the barriers to determine the magnitude and anisotropy of long-range diffusion. Our findings suggest highly anisotropic mass transport in hematite, favoring diffusion along the c-axis of the crystal. In addition, we have considered the point defect formation energetics using the largest Fe2O3 supercell reported to date.

Sustainable and energy-efficient ammonia production is of direct interest for a range of applications including production of inorganic fertilizers, energy storage and chemical feedstock. Going beyond the Haber Bosch process, a decentralization of catalytic ammonia production requires new and improved electrocatalysts that can produce ammonia at relatively low temperatures and ambient pressure. In recent past, zirconium nitride has emerged as a potential candidate catalyst for electrochemical reduction of N2 to ammonia. However, the effect of local composition (e.g., doping by oxygen to go to zirconium oxynitride) and configuration (e.g., surface steps leading to under-coordinated surface Zr and N sites) on the catalytic performance is not well understood. Here, we use systematic density functional theory computations to study energetics and electronic structure of the intermediates involved in the various elementary reactions associated with the electrochemical reduction of dinitrogen to ammonia. Our study provides a comparative analysis of the (100) pristine zirconium nitride, pristine zirconium oxynitride and stepped zirconium nitride surfaces. We find that the potential-determining step is highly sensitive toward the type of the surface considered and can change significantly going from one surface to the other. However, surface N vacancy formation is always the rate-determining step, which shows a tradeoff with the NH3 desorption step and can be tuned by changing the N chemical potential. Lastly, the stability and kinetics of the surface nitrogen vacancy against the subsurface diffusion as well as its poisoning due to other competing adsorbates such as H, O and OH species in an electrochemical environment is considered. Overall, our results provide atomic-level understanding of the ZrN surface chemistry and surface structure-dependent activity toward nitrogen reduction reaction for ammonia synthesis.

Under ambient conditions, nitrogen reduction to ammonia through electrochemical reactions could be a promising strategy to circumvent the energy and capital-intensive commercial Haber−Bosch (HB) process. But developing suitable catalysts to compete with the similar reaction rate of the commercial HB process is the main bottleneck. In this paper, 3d, 4d, and 5d transition metals anchored on χ3 borophene have been considered as single-atom catalysts for ammonia synthesis. Comprehensive computational screening and systematic evaluation have been carried out to understand the catalytic activity and selectivity of these catalysts through two different reaction pathways: distal and alter. Fe and Mn-based SAC has the lowest overpotential (0.64 V and 0.79 V) in the distal and alter process, respectively. These catalysts also has depicted better selectivity to NRR compared to HER.

Organic electrode materials are becoming increasingly important as they reduce the C-footprint as well as the production cost of currently used and studied rechargeable batteries. With increasing demand for high-energy-density devices, over the past few decades, various innovative new materials based on the fundamental structure-property relationships and molecular design have been explored to enable high-capacity next-generation battery chemistries. One critical dimension that catalyzes this study is the building up of an in-depth understanding of the structure-property relationship and mechanism of alkali ion batteries. In this review, we present a critical overview of the progress in the technical feasibility of organic battery electrodes for use in long-term and large-scale electrical energy-storage devices based on the materials designing, working mechanisms, performance, and battery safety. Specifically, we discuss the underlying alkali ion storage mechanisms in specific organic batteries, which could provide the designing requirements to overcome the limitations of organic batteries. We also discuss the promising future research directions in the field of alkali ion organic batteries, especially multivalent organic batteries along with monovalent alkali ion organic batteries.

A simple approach was employed to fabricate hybrid titanium dioxide (TiO2) nanoparticles and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) embedded with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and carbon quantum dots (CQDs) on a p-type of silicon (p-Si) substrate by utilizing the drop-casting method. The structural analysis was conducted using Raman spectroscopy. A UV radiation source with a wavelength of 365 nm and an intensity of 200 mW cm−2 was utilized to observe the alteration in conductivity under both illuminated and non-illuminated conditions. The device consisting of TiO2/PEDOT:PSS/LiTFSI demonstrated a responsivity of 25.3%, and the response/recovery times were obtained to be 467/577 seconds, respectively. The responsivity of the CQDs:TiO2/PEDOT:SS/LiTFSI device was measured to be 22.2%, and the response/recovery times were found to be 300/393 seconds, respectively. The design methodology employed in our approach holds promise for application in the fabrication of different sensors capable of detecting harmful UV rays, which is known to contribute to premature aging, sunburn, cataracts, skin cancer, and a range of other UV-related dermatological conditions.