Tailoring the Interfacial Water Structure by Electrolyte Engineering for Selective Electrocatalytic Reduction of Carbon Dioxide

Open Access via the ACS Agreement Department of Atomic Energy, Government of India - RTI4007 ACKNOWLEDGMENTS N.M. and T.N.N. acknowledge the support of the Department of Atomic Energy, Government of India, under Project Identification No. RTI4007. N.M. acknowledges the funding support of Infosys Foundation through Infosys� TIFR Leading Edge Travel Grant. N.M. acknowledges Dr. Anku Guha and Dr. Andrew Burley for useful discussions. A.C. acknowledges the continued support of the University of Aberdeen.Peer reviewedPublisher PD

MoS2/MoO3 Heterojunction: Dual Role of the Type II set-up and Band Gap Modulation of MoS2 upon Lithium-Ion Intercalation

In recent times photorechargeable metal ion batteries have garnered significant attention but the atomistic details of the mechanism of the charging process is still unknown. MoS2/MoOy, a type II semiconductor heterostructure, has been shown to function as photocathode where during discharge the lithium ion (Li-ion) intercalation happens mostly in MoS2 layers. Photoexposure leads to exciton formation and the type II set-up is supposed to generate spatially separated and longer-lived charge carriers. The Li intercalated MoS2 is known to undergo a phase transition from the semiconducting (2H) to a metallic (1T') phase. Hence, the proposal of exciton formation and its separation in LixMoS2 during photocharging needs closer inspection. In this study, with the help of density functional theory (DFT) based studies that is aptly supported by experimental data, it is shown that LixMoS2/MoO3 forms a type II heterostructure where the underlying band gap of LixMoS2 is exposed due to dispersion of electron density onto MoO3 upto a certain value of x. Further studies show that the type II arrangement is lost prior to the phase transition. In order to investigate the electronic structure and the phase transition upon lithiation in the explicit heterostructure, we introduced two unconventional computational schemes. The presence of the band gap and the ensuing type II arrangement in LixMoS2/MoO3 upto a certain concentration of the intercalated Li-ion justifies the possibility of the photocharging process. We believe that the general concepts explored in this study will be important in the rational design of type II heterostructures that can behave as photo-cathode materials in Li-ion batteries

An Atomistic View of Electrodics at the Platinum Surface

Platinum (Pt) is a benchmarked catalyst for several electrochemical processes, however an atomistic insight into its electrodics at the electrode-electrolyte interface is still lacking. In this study, we aim to capture the chemical changes of Pt surfaces brought on by an applied potential in an electrolyte of pH~5, which can address the catalytic efficacy and stability of different crystallographic orientations under varying applied bias. Through a combined experimental and reactive molecular dynamics simulation approach, we uncover the effect of charge build up on the surface of the Pt electrode, which can be directed towards capacitive and faradaic processes. By introducing a simulated applied potential, which is compared to experimental potential by equating charge density ( in the range -0.2 mC/cm2 to 0.2 mC/cm2 ), we unravel the electrochemical processes on Pt (in slightly acidic pH). At reductive potentials of ~0.3-0.0 V vs RHE, we visualize phenomenon such as under potential hydrogen adsorption (HUPD) and hydrogen evolution/oxidation reaction. While oxidative potentials in the range ~1.2-1.6 V vs RHE see platinum oxide (Pt-O) formation, and platinum leaching off the surface. The theoretical potential and plane dependence of these phenomenon (HUPD, Pt-O, etc.) are verified with experiments, and hence it brings a new platform for computationally viable electrode-electrolyte studies.</div

Ultra-Low Loaded Platinum Bonded Hexagonal Boron Nitride as Stable Electrocatalyst for Hydrogen Generation

Chemical stability of hexagonal boron nitride (hBN) ultra-thin layers in harsh electrolytes and the availability of nitrogen site to stabilize metals like Pt are used here to develop a high intrinsic activity hydrogen evolution reaction (HER) catalyst having low loaded Pt (5 weight% or < 1 atomic%). A catalyst having non-zero oxidation state for Pt (with a Pt-N bonding) is shown to be HER active even with low catalyst loadings (0.114 mgcm-2). Electronic modification of the shear exfoliated hBN sheets is achieved by Au nanoparticle-based surface decoration (hBN_Au), and further anchoring with Pt develops a catalyst (hBN_Au_Pt) with high turnover frequency for HER (~15), which is ~1.8 times higher than the benchmarked Pt/C HER catalyst. The hBN_Au_Pt is shown to be a highly durable catalyst even after the accelerated durability test for 10000 cycles and temperature annealing of 100 oC. Density functional theory-based calculations gave insights in to the electronic modifications of hBN with Au and the catalytic activity of the hBN_Au_Pt system, in line with the experimental studies, indicating the demonstration of a new class of catalyst system devoid of issues such as carbon corrosion and Pt leaching