131 research outputs found
Data for "Tailoring Hot-Carrier Distributions of Plasmonic Nanostructures through Surface Alloying"
No full text<p>This upload includes the data presented and analyzed in the article "Tailoring Hot-Carrier Distributions of Plasmonic Nanostructures through Surface Alloying" by Jakub Fojt, Tuomas P. Rossi, Priyank V. Kumar, and Paul Erhart.</p>
<p>The codes for reproducing the data are provided at <a href="https://doi.org/10.5281/zenodo.10663218">doi:10.5281/zenodo.10663218</a>.</p>
<p>See <em>README.md</em> in <em>data.zip</em> for a detailed description.</p>
Graphene Oxide as a Promising Hole Injection Layer for MoS[subscript 2]-based Electronic Devices
No full textThe excellent physical and semiconducting properties of transition metal dichalcogenide (TMDC) monolayers make them promising materials for many applications. The TMDC monolayer MoS[subscript 2] has gained significant attention as a channel material for next-generation transistors. However, while n-type single-layer MoS2 devices can be made with relative ease, fabrication of p-type transistors remains a challenge as the Fermi-level of elemental metals used as contacts are pinned close to the conduction band leading to large p-type Schottky barrier heights (SBH). Here, we propose the utilization of graphene oxide (GO) as an efficient hole injection layer for single-layer MoS[subscript 2]-based electronic and optoelectronic devices. Using first-principles computations, we demonstrate that GO forms a p-type contact with monolayer MoS[subscript 2], and that the p-type SBH can be made smaller by increasing the oxygen concentration and the fraction of epoxy functional groups in GO. Our analysis shows that this is possible due to the high work function of GO and the relatively weak Fermi-level pinning at the MoS[subscript 2]/GO interfaces compared to traditional MoS[subscript 2]/metal systems (common metals are Ag, Al, Au, Ir, Pd, Pt). The combination of easy-to-fabricate and inexpensive GO with MoS[subscript 2] could be promising for the development of hybrid all-2D p-type electronic and optoelectronic devices on flexible substrates.Eni S.p.A. (Firm) (Eni-MIT Alliance Solar Frontiers Program
Nanocarbon-Based Photovoltaics
No full textCarbon materials are excellent candidates for photovoltaic solar cells: they are Earth-abundant, possess high optical absorption, and maintain superior thermal and photostability. Here we report on solar cells with active layers made solely of carbon nanomaterials that present the same advantages of conjugated polymer-based solar cells, namely, solution processable, potentially flexible, and chemically tunable, but with increased photostability and the possibility to revert photodegradation. The device active layer composition is optimized using ab initio density functional theory calculations to predict type-II band alignment and Schottky barrier formation. The best device fabricated is composed of PC[subscript 70]BM fullerene, semiconducting single-walled carbon nanotubes, and reduced graphene oxide. This active-layer composition achieves a power conversion efficiency of 1.3%—a record for solar cells based on carbon as the active material—and we calculate efficiency limits of up to 13% for the devices fabricated in this work, comparable to those predicted for polymer solar cells employing PCBM as the acceptor. There is great promise for improving carbon-based solar cells considering the novelty of this type of device, the high photostability, and the availability of a large number of carbon materials with yet untapped potential for photovoltaics. Our results indicate a new strategy for efficient carbon-based, solution-processable, thin film, photostable solar cells.MIT Energy Initiative Seed FundIntel Corporation (Intel Ph.D. Fellowship
Interface-Controlled Phase Separation of Liquid Metal-Based Eutectic Ternary Alloys
No full textLiquid metals (LMs) are immiscible in many common electrolytic
solutions and, when immersed in them, establish phase boundaries that
display intriguing interfacial characteristics. The application of
a cathodic potential to such interfaces may trigger phase separation
of solute elements out of the LMs. Here, we investigate this possibility
in two of the most researched and industrially used eutectic ternary
LMs of Galinstan (Ga-In-Sn) and Field’s metal (FM, In–Bi–Sn).
We observe that upon surface perturbation by an applied electric potential,
solute elements compete to segregate out of the LM alloys according
to their energy levels. The nature of the electrolytic solutions plays
a key role in the separation process as they dictate whether solute
metals are expelled selectively in their pure form or as binary compounds.
For example, in a phosphate-based aqueous electrolyte, nano-sized
Sn-based entities are selectively expelled from Galinstan, while only
Bi-based structures leave the surface of FM. In contrast, in a non-aqueous
electrolyte, nano-sized binary compounds of Sn–In and Bi–Sn
are separated from the surfaces of Galinstan and FM, respectively.
We show that selectivity in the surface separation process, achieved
by the alteration of the electrolytic solutions, is due to the interplay
between the electrodynamic interactions and the electrocapillary effect.
This study presents two key findings: (a) it is essential to carefully
consider the possibility of component separation in electrochemical
systems based on LMs and (b) it demonstrates interfacial metallurgical
pathways to process alloys for refining metals into specific purities,
component ratios, and dimensions
Enhanced Nitrate-to-Ammonia Activity on Fe/ZnO Nanoparticles via Tuning Intermediate Adsorption in Alkaline Electrolyte
No full textThe electrocatalytic recycling of waste nitrate (NO3RR) is a promising decentralized route for green ammonia synthesis. Nonetheless, it suffers from the competing hydrogen evolution reaction and the insufficient proton supply in high pH conditions. Herein, iron oxide nanoparticles anchored on ZnO is introduced as a strategy to enhance the water dissociation ability and proton transfer rate, advancing NH4 + production from alkaline NO3RR. Supported by a set of ex situ and in situ characterization, the findings reveal the reduction of iron oxides, along with improvements in charge transfer properties and proton generation from H2O. Theoretical calculations show that iron oxides reduce the kinetic barrier of the rate-limiting step (*NO2-to-*NO2H) and result in a thermodynamically favorable process to hydrogenation steps, which in turn reduce the overall energy barrier of alkaline NO3RR. Optimal catalytic activity is realized with a Fe loading of 0.5 wt.%, delivering a Faradaic efficiency of ≈83% for ammonium with a NH4 + yield rate of 31 nmol s−1 cm−2 at −0.7 V versus RHE. The results pave the way for the utilization of bi-metal interaction to tune the reaction pathway for achieving sustainable ammonium synthesis in alkaline, contributing to ongoing efforts to achieve a sustainable nitrogen cycle via N-based electrochemistry.Thanh Son Bui, Zhipeng Ma, Jodie A. Yuwono, Priyank V. Kumar, George E.P. O, Connell, Lingyi Peng, Yuwei Yang, Maggie Lim, Rahman Daiyan, Emma C. Lovell, and Rose Ama
Cr-dopant induced crystal orientation and shape modulation in Ni<sub>2</sub>P nanocrystals for improving electrosynthesis of methanol to formate coupled with hydrogen production
No full textSimultaneously improving the electrochemical methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER) using the electrolysis technique is a significant yet challenging task. To tackle this, we report a colloidal synthesis of Cr-dopant induced crystal orientation and shape modulation in Ni2P nanocrystals (NCs) as an advanced bifunctional electrocatalyst for electrosynthesis of value-added formate from the MOR at the anode and hydrogen at the cathode. We demonstrate that a two-electrode overall methanol splitting (OMeS) system using Cr-doped Ni2P nanorods (NRs) as a bifunctional catalyst can achieve a lowest voltage of 1.16 V to reach a current density of 10 mA cm−2 , compared to the cell voltage of 1.65 V for overall water splitting. Combined experimental and theoretical investigations revealed that the Cr-dopant induces shape modulation and crystal orientation in Ni2P, which favors the thermodynamics of the dehydrogenation process in the MOR and hydrogen adsorption in the HER, leading to enhanced electrocatalytic activities. Interestingly, a proof-of-concept solar-driven system fabricated using a commercial Si photovoltaic cell integrated with an OMeS cell employing bifunctional Cr-doped Ni2P NRs generated a stable photocurrent density of ∼12.3 mA cm−2 for 60 min., demonstrating its promise for energy-efficient and selective electrosynthesis, enabling the production of valuable chemicals and clean hydrogen in a sustainable manner.Umesh P. Suryawanshi, Uma V. Ghorpade, Jodie A. Yuwono, Priyank V. Kumar, Mayur A. Gaikwad, Seung Wook Shin, Jun Sung Jang, Hyo Rim Jung, Mahesh P. Suryawanshi, and Jin Hyeok Ki
Unraveling the structure-activity-selectivity relationships in furfuryl alcohol photoreforming to H2 and hydrofuroin over ZnxIn2S3+x photocatalysts
No full textZnxIn2S3+x has emerged as a promising candidate for alcohol photoreforming based on C-H activation and C-C coupling. However, the underlying structure-activity-selectivity relationships remain unclear. Here we report on ZnxIn2S3+x with varying Zn:In:S ratios for visible-light-driven furfuryl alcohol reforming into H2 and hydrofuroin, a jet fuel precursor, via C-H activation and C-C coupling. S-• radicals are directly identified as the catalytically active sites responsible for C-H activation in furfuryl alcohol, promoting selectivity toward H2 and hydrofuroin. The optimum ZnxIn2S3+x activity derives from a trade-off between enhanced carrier dynamics and diminished visible light absorption as the x value in ZnxIn2S3+x increases. Further, a higher Zn-S:In-S layer ratio prolongs the S-• lifetime in the Zn-S layer, promoting C-H activation and delivering a higher C-C coupling product selectivity. The findings represent a step toward further establishing sulfide-based photocatalysts for sustainable H2 production via organic photoreforming.Denny Gunawan, Jodie A. Yuwono, Priyank V. Kumar, Akasha Kaleem, Michael P. Nielsen, Murad J.Y. Tayebjee, Louis Oppong-Antwi, Haotian Wen, Inga Kuschnerus, Shery L.Y. Chang, Yu Wang, Rosalie K. Hocking, Ting-Shan Chan, Cui Ying Toe, Jason Scott, Rose Ama
Atomically Dispersed Cu Catalysts on Sulfide-Derived Defective Ag Nanowires for Electrochemical CO2 Reduction
No full textPublished: February 2, 2023Single-atom catalysts (SACs) have shown potential for achieving an efficient electrochemical CO2 reduction reaction (CO2RR) despite challenges in their synthesis. Here, Ag2S/Ag nanowires provide initial anchoring sites for Cu SACs (Cu/Ag2S/Ag), then Cu/Ag(S) was synthesized by an electrochemical treatment resulting in complete sulfur removal, i.e., Cu SACs on a defective Ag surface. The CO2RR Faradaic efficiency (FECO2RR) of Cu/Ag(S) reaches 93.0% at a CO2RR partial current density (jCO2RR) of 2.9 mA/cm2 under −1.0 V vs RHE, which outperforms sulfur-removed Ag2S/Ag without Cu SACs (Ag(S), 78.5% FECO2RR with 1.8 mA/cm2jCO2RR). At −1.4 V vs RHE, both FECO2RR and jCO2RR over Cu/Ag(S) reached 78.6% and 6.1 mA/cm2, which tripled those over Ag(S), respectively. As revealed by in situ and ex situ characterizations together with theoretical calculations, the interacted Cu SACs and their neighboring defective Ag surface increase microstrain and downshift the d-band center of Cu/Ag(S), thus lowering the energy barrier by ∼0.5 eV for *CO formation, which accounts for the improved CO2RR activity and selectivity toward related products such as CO and C2+ products.Zhipeng Ma, Tao Wan, Ding Zhang, Jodie A. Yuwono, Constantine Tsounis, Junjie Jiang, Yu-Hsiang Chou, Xunyu Lu, Priyank V. Kumar, Yun Hau Ng, Dewei Chu, Cui Ying Toe, Zhaojun Han, and Rose Ama
Seeing the light: The role of cobalt in light-assisted CO(2) methanation
No full textIlluminating thermal catalysts with visible light is an effective strategy to reduce the thermal requirements of CO₂ methanation. In this study, we systematically varied the cobalt loading and properties of xCo/CeO₂ catalysts (between 0 and 10 wt%) to understand changes in the visible light-assisted reaction mechanism with cobalt loading. 10Co/CeO₂ had the highest CO₂ conversion of 90% at 450 ◦C. The light promoted the CO₂ conversion of all catalysts from 300 to 450◦C, peaking for 7.5Co/CeO₂ with a 125% improvement relative to thermal conditions (300 ◦C) before diminishing for 10Co/CeO₂. The light facilitated the conversion of the formate intermediate adsorbed onto CeO₂. In-situ DRIFTS and DFT unveiled a particle size trade-off between maximising CO₂ adsorbed at the Co-Ce interface while minimising CO₂ adsorbed onto cobalt, which is required for the best light enhancement. These findings underscore the importance of careful deposit size optimisation to unlock the lightassisted methanation’s full potential.George E.P. O, Connell, Tze Hao Tan, Jodie A. Yuwono, Yu Wang, Amanj Kheradmand, Yijiao Jiang, Priyank V. Kumar, Rose Amal, Jason Scott, Emma C. Lovel
Ru-Induced Defect Engineering in Co3O4 Lattice for High Performance Electrochemical Reduction of Nitrate to Ammonium
No full textAmidst these growing sustainability concerns, producing NH4 + via electrochemical NO3 − reduction reaction (NO3RR) emerges as a promising alternative to the conventional Haber-Bosch process. In a pioneering approach, this study introduces Ru incorporation into Co3O4 lattices at the nanoscale and further couples it with electroreduction conditioning (ERC) treatment as a strategy to enhance metal oxide reducibility and induce oxygen vacancies, advancing NH4 + production from NO3RR. Here, supported by a suite of ex situ and in situ characterization measurements, the findings reveal that Ru enrichment promotes Co species reduction and oxygen vacancy formation. Further, as evidenced by the theoretical calculations, Ru integration lowers the energy barrier for oxygen vacancy formation, thereby facilitating a more energy-efficient NO3RR-to-NH4 + pathway. Optimal catalytic activity is realized with a Ru loading of 10 at.% (named 10Ru/Co3O4), achieving a high NH4 + production rate (98 nmol s−1 cm−2), selectivity (97.5%) and current density (≈100 mA cm−2) at −1.0 V vs RHE. The findings not only provide insights into defect engineering via the incorporation of secondary sites but also lay the groundwork for innovative catalyst design aimed at improving NH4 + yield from NO3RR. This research contributes to the ongoing efforts to develop sustainable electrochemical processes for nitrogen cycle management.Maggie Lim, Zhipeng Ma, George O'Connell, Jodie A. Yuwono, Priyank Kumar, Rouhollah Jalili, Rose Amal, Rahman Daiyan, and Emma C. Lovel
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