Molybdenum Disulfide Catalytic Coatings via Atomic Layer Deposition for Solar Hydrogen Production from Copper Gallium Diselenide Photocathodes

We demonstrate that applying atomic layer deposition-derived molybdenum disulfide (MoS2) catalytic coatings on copper gallium diselenide (CGSe) thin film absorbers can lead to efficient wide band gap photocathodes for photoelectrochemical hydrogen production. We have prepared a device that is free of precious metals, employing a CGSe absorber and a cadmium sulfide (CdS) buffer layer, a titanium dioxide (TiO2) interfacial layer, and a MoS2 catalytic layer. The resulting MoS2/TiO2/CdS/CGSe photocathode exhibits a photocurrent onset of +0.53 V vs RHE and a saturation photocurrent density of -10 mA cm-2, with stable operation for >5 h in acidic electrolyte. Spectroscopic investigations of this device architecture indicate that overlayer degradation occurs inhomogeneously, ultimately exposing the underlying CGSe absorber

Highly Stable Molybdenum Disulfide Protected Silicon Photocathodes for Photoelectrochemical Water Splitting

© 2017 American Chemical Society. Developing materials, interfaces, and devices with improved stability remains one of the key challenges in the field of photoelectrochemical water splitting. As a barrier to corrosion, molybdenum disulfide is a particularly attractive protection layer for photocathodes due to its inherent stability in acid, the low permeability of its basal planes, and the excellent hydrogen evolution reaction (HER) activity the MoS2 edge. Here, we demonstrate a stable silicon photocathode containing a protecting layer consisting of molybdenum disulfide, molybdenum silicide, and silicon oxide which operates continuously for two months. We make comparisons between this system and another molybdenum sulfide-silicon photocathode embodiment, taking both systems to catastrophic failure during photoelectrochemical stability measurements and exploring mechanisms of degradation. X-ray photoelectron spectroscopy and transmission electron microscopy provide key insights into the origins of stability

Investigating Catalyst–Support Interactions To Improve the Hydrogen Evolution Reaction Activity of Thiomolybdate [Mo3S13]2– Nanoclusters

© 2017 American Chemical Society. Molybdenum sulfides have been identified as promising materials for catalyzing the hydrogen evolution reaction (HER) in acid, with active edge sites that exhibit some of the highest turnover frequencies among nonpreciousmetal catalysts. The thiomolybdate [Mo 3 S 13 ] 2- nanocluster catalyst contains a structural motif that resembles the active site of MoS2 and has been reported to be among the most active forms of molybdenum sulfide. Herein, we improve the activity of the [Mo 3 S 13 ] 2- catalysts through catalyst-support interactions. We synthesize [Mo 3 S 13 ] 2- on gold, silver, glassy carbon, and copper supports to demonstrate the ability to tune the hydrogen binding energy of [Mo 3 S 13 ] 2- using catalyst-support electronic interactions and optimize HER activity

Ultrahigh-current-density niobium disulfide catalysts for hydrogen evolution

Metallic transition metal dichalcogenides (TMDs)1???8 are good catalysts for the hydrogen evolution reaction (HER). The overpotential and Tafel slope values of metallic phases and edges9 of two-dimensional (2D) TMDs approach those of Pt. However, the overall current density of 2D TMD catalysts remains orders of magnitude lower (~10???100 mA cm???2) than industrial Pt and Ir electrolysers (>1,000 mA cm???2)10,11. Here, we report the synthesis of the metallic 2H phase of niobium disulfide with additional niobium (2H Nb1+xS2, where x is ~0.35)12 as a HER catalyst with current densities of >5,000 mA cm???2 at ~420 mV versus a reversible hydrogen electrode. We find the exchange current density at 0 V for 2H Nb1.35S2 to be ~0.8 mA cm???2, corresponding to a turnover frequency of ~0.2 s???1. We demonstrate an electrolyser based on a 2H Nb1+ xS2 cathode that can generate current densities of 1,000 mA cm???2. Our theoretical results reveal that 2H Nb1+ xS2 with Nb-terminated surface has free energy for hydrogen adsorption that is close to thermoneutral, facilitating HER. Therefore, 2H Nb1+ xS2 could be a viable catalyst for practical electrolysers

Identification of distinct nanoparticles and subsets of extracellular vesicles by asymmetric flow field-flow fractionation

The heterogeneity of exosomal populations has hindered our understanding of their biogenesis, molecular composition, biodistribution and functions. By employing asymmetric flow field-flow fractionation (AF4), we identified two exosome subpopulations (large exosome vesicles, Exo-L, 90-120 nm; small exosome vesicles, Exo-S, 60-80 nm) and discovered an abundant population of non-membranous nanoparticles termed 'exomeres' (~35 nm). Exomere proteomic profiling revealed an enrichment in metabolic enzymes and hypoxia, microtubule and coagulation proteins as well as specific pathways, such as glycolysis and mTOR signalling. Exo-S and Exo-L contained proteins involved in endosomal function and secretion pathways, and mitotic spindle and IL-2/STAT5 signalling pathways, respectively. Exo-S, Exo-L and exomeres each had unique N-glycosylation, protein, lipid, DNA and RNA profiles and biophysical properties. These three nanoparticle subsets demonstrated diverse organ biodistribution patterns, suggesting distinct biological functions. This study demonstrates that AF4 can serve as an improved analytical tool for isolating extracellular vesicles and addressing the complexities of heterogeneous nanoparticle subpopulations.The authors also acknowledge the Genomics Resource Core facility (WCM) for their high-quality service. The authors thank C. Ghajar and J. Weiss for feedback on the manuscript and members of the Lyden laboratory for discussions. Our study was supported by the National Cancer Institute (U01-CA169538 to D.L.), the National Institutes of Health (NIH; R01-CA169416 to D.L. and H.P.; R01-CA218513 to D.L. and H.Z.), the US Department of Defense (W81XWH-13-10249 to D.L.), W81XWH-13-1-0425 (to D.L., J.Br.), the Sohn Conference Foundation (D.L., I.M., H.P. and H.Z.), the Children’s Cancer and Blood Foundation (D.L.), The Manning Foundation (A.H. and D.L.), The Hartwell Foundation (D.L.), The Nancy C. and Daniel P. Paduano Foundation (D.L.), The Starr Cancer Consortium (H.P. and D.L.; D.L. and H.Z.), the Pediatric Oncology Experimental Therapeutic Investigator Consortium (POETIC; D.L.), the James Paduano Foundation (D.L. and H.P.), the NIH/WCM CTSC (NIH/NCATS: UL1TR00457 to H.M. and H.Z.; UL1TR002384 to D.L., H.M. and H.Z.), the Malcolm Hewitt Wiener Foundation (D.L.), the Champalimaud Foundation (D.L.), the Thompson Family Foundation (D.L., R.S.), U01-CA210240 (D.L.), the Beth Tortolani Foundation (J.Br.), the Charles and Marjorie Holloway Foundation (J.Br.), the Sussman Family Fund (J.Br.), the Lerner Foundation (J.Br.), the Breast Cancer Alliance (J.Br.), the Manhasset Women’s Coalition Against Breast Cancer (J.Br.), the National Institute on Minority Health and Health Disparities (NIMHD) of the NIH (MD007599 to H.M.), NIH/NCATS (UL1TR00457 to H.M.). C.R., A.M., D.F., A.F., A.S. and H.O. acknowledge FEDER (Fundo Europeu de Desenvolvimento Regional funds through COMPETE 2020) POCI, Portugal 2020 (NORTE-01-0145-FEDER-000029) and FCT – Fundação para a Ciência e a Tecnologia in the framework of the project ‘Institute for Research and Innovation in Health Sciences’ (POCI-01-0145-FEDER-007274) and the FCT project POCI-01-0145-FEDER-016585 (PTDC/BBB-EBI/0567/2014). The authors acknowledge FCT for grants to A.M. (SFRH/BPD/75871/2011) and A.F. (SFRH/BPD/111048/2015). D.F. acknowledges FCT (SFRH/BD/110636/2015), the BiotechHealth PhD Programme (PD/0016/2012) and the American Portuguese Biomedical Research Fund.S