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  • Journal article
    Kumar S, Regue M, Isaacs M, Freeman E, Eslava Set al., 2020,

    All-Inorganic CsPbBr3 nanocrystals: gram-scale mechanochemical synthesis and selective photocatalytic CO2 reduction to methane

    , ACS Applied Energy Materials, Vol: 3, Pages: 4509-4522, ISSN: 2574-0962

    Halide perovskite CsPbBr3 has recently gained wide interest for its application in solar cells, optoelectronics and artificial photosynthesis, but further progress is needed to develop greener and more scalable synthesis procedures and for their application in humid environments. Herein, we report a fast and convenient mechanochemical synthesis of CsPbBr3 perovskite nanocrystals with scale-up capability and control over crystal size and morphology. These perovskite nanocrystals show excellent crystallinity and tunable morphologies, from nanorods to nanospheres and nanosheets, simply changing the mechanochemical reaction conditions such as ball milling time, ball size and Cs precursor. Furthermore, we explore their use for gas-phase photocatalytic CO2 reduction using water vapor as proton source. A photocatalytic conversion of CO2 and H2O(g) to 0.43 (0.03) μmol CH4 g-1 h-1, 2.25 (0.09) μmol CO g-1 h-1 and 0.08 (0.02) μmol H2 g-1 h-1 was for example achieved with CsPbBr3 nanosheets and simulated sunlight, keeping 30% of this activity over three consecutive cycles. When these CsPbBr3 nanosheets were mechanochemically prepared together with Cu-loaded reduced graphene oxide (Cu-RGO), the photocatalytic activity significantly improved to 12.7 (0.95) μmol CH4 g-1 h-1, 0.46 (0.11) μmol CO g-1 h-1 and 0.27 (0.02) μmol H2 g-1 h-1, and a 90% of this activity was retained over three consecutive cycles. The selectivity for CH4 increased to 98.5(0.93)% on an electron basis and a remarkable apparent quantum efficiency of 1.10(0.15)% at 523 nm was achieved. This enhanced activity, selectivity and stability were assigned to the better charge separation, visible light absorption, CO2 adsorption & activation, and hydrophobic character of the obtained composites. These results will contribute to the rational design and application of halide perovskites for CO2 photocatalytic reduction.

  • Journal article
    Freeman E, Kumar S, Thomas SR, Pickering H, Fermin DJ, Eslava Set al., 2020,

    PrFeO3 Photocathodes Prepared Through Spray Pyrolysis

    , CHEMELECTROCHEM, Vol: 7, Pages: 1365-1372, ISSN: 2196-0216
  • Journal article
    Rood S, Eslava S, Manigrasso A, Bannister Cet al., 2020,

    Recent advances in gasoline three-way catalyst formulation: A review

  • Journal article
    Freeman E, Kumar S, Celorrio V, Park MS, Kim JH, Fermin DJ, Eslava Set al., 2019,

    Strategies for deposition of LaFeO3 photocathodes: improving photocurrent with a polymer template

    , Sustainable Energy and Fuels, Vol: 4, Pages: 884-894, ISSN: 2398-4902

    Renewable and sustainable alternatives to fossil fuels are needed to limit the impact of global warming. Using metal oxide semiconductors as photoelectrodes within photoelectrochemical cell devices, in which solar energy can be stored and ultimately used for electricity generation, is one such alternative. LaFeO3 (LFO) has been shown to be an active photocathode on illumination of visible light but is restricted by low surface area and relatively low photocurrents achieved. The work herein utilizes a spin coating deposition method with a solution of nitrate precursors combined with non-ionic polymeric surfactant (Triton X-100). This allowed for the formation of a uniform porous LFO film of high coverage on a fluorine-doped tin oxide coated substrate, through directing growth and preventing particle aggregation during film fabrication. These porous LFO films achieved an enhanced photocurrent of -161±6 µA cm-2 at +0.43 VRHE, in addition to a remarkable high onset potential of +1.4 VRHE for cathodic photocurrent. It was additionally shown that this attained film quality and activity was superior to other film fabrication methods such as doctor blading and spray pyrolysis. With this polymer templating method for LFO films, not only are higher photocurrents achieved but there are also added benefits such as better charge separation, higher efficiencies, higher specific electrochemically-active surface area and improved stability.

  • Journal article
    Regue M, Sibby S, Ahmet IY, Friedrich D, Abdi FF, Johnson AL, Eslava Set al., 2019,

    TiO2 photoanodes with exposed {010} facets grown by aerosol-assisted chemical vapor deposition of a titanium oxo/alkoxy cluster

    , JOURNAL OF MATERIALS CHEMISTRY A, Vol: 7, Pages: 19161-19172, ISSN: 2050-7488
  • Journal article
    Zhang J, Eslava S, 2019,

    Understanding charge transfer, defects and surface states at hematite photoanodes

    , SUSTAINABLE ENERGY & FUELS, Vol: 3, Pages: 1351-1364, ISSN: 2398-4902
  • Journal article
    Poli I, Hintermair U, Regue M, Kumar S, Sackville EV, Baker J, Watson TM, Eslava S, Cameron PJet al., 2019,

    Graphite-protected CsPbBr3 perovskite photoanodes functionalised with water oxidation catalyst for oxygen evolution in water

    , Nature Communications, Vol: 10, Pages: 1-10, ISSN: 2041-1723

    Metal-halide perovskites have been widely investigated in the photovoltaic sector due to their promising optoelectronic properties and inexpensive fabrication techniques based on solution processing. Here we report the development of inorganic CsPbBr3-based photoanodes for direct photoelectrochemical oxygen evolution from aqueous electrolytes. We use a commercial thermal graphite sheet and a mesoporous carbon scaffold to encapsulate CsPbBr3 as an inexpensive and efficient protection strategy. We achieve a record stability of 30 h in aqueous electrolyte under constant simulated solar illumination, with currents above 2 mA cm−2 at 1.23 VRHE. We further demonstrate the versatility of our approach by grafting a molecular Ir-based water oxidation catalyst on the electrolyte-facing surface of the sealing graphite sheet, which cathodically shifts the onset potential of the composite photoanode due to accelerated charge transfer. These results suggest an efficient route to develop stable halide perovskite based electrodes for photoelectrochemical solar fuel generation.

  • Conference paper
    Zhang Y, Kumar S, Marken F, Krasny M, Roake E, Eslava S, Dunn S, Da Como E, Bowen CRet al., 2019,

    Pyro-electrolytic water splitting for hydrogen generation

    , 4th International Conference on Nanogenerator and Piezotronics (NGPT), Publisher: ELSEVIER SCIENCE BV, Pages: 183-191, ISSN: 2211-2855
  • Conference paper
    Kumar S, Poli I, Isaacs MA, Regue M, Eslava Set al., 2019,

    Mechanochemical synthesis of all-Inorganic CsPbBr3 nanorods and their use in selective photocatalytic hydrogenation of CO2

    , National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
  • Journal article
    Walsh D, Zhang J, Regue M, Dassanayake R, Eslava Set al., 2019,

    Simultaneous Formation of FeOx Electrocatalyst Coating within Hematite Photoanodes for Solar Water Splitting

    , ACS APPLIED ENERGY MATERIALS, Vol: 2, Pages: 2043-2052, ISSN: 2574-0962
  • Journal article
    Castresana PA, Martinez SM, Freeman E, Eslava S, Di Lorenzo Met al., 2019,

    Electricity generation from moss with light-driven microbial fuel cells

    , ELECTROCHIMICA ACTA, Vol: 298, Pages: 934-942, ISSN: 0013-4686
  • Journal article
    Rood SC, Ahmet HB, Gomez-Ramon A, Torrente-Murciano L, Reina TR, Eslava Set al., 2019,

    Enhanced ceria nanoflakes using graphene oxide as a sacrificial template for CO oxidation and dry reforming of methane

    , APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 242, Pages: 358-368, ISSN: 0926-3373
  • Journal article
    Jo W-K, Kumar S, Eslava S, Tonda Set al., 2018,

    Construction of Bi2WO6/RGO/g-C3N4 2D/2D/2D hybrid Z-scheme heterojunctions with large interfacial contact area for efficient charge separation and high-performance photoreduction of CO2 and H2O into solar fuels

    , APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 239, Pages: 586-598, ISSN: 0926-3373
  • Journal article
    Regue M, Armstrong K, Walsh D, Richards E, Johnson AL, Eslava Set al., 2018,

    Mo-doped TiO2 photoanodes using [Ti4Mo2O8(OEt)(10)](2) bimetallic oxo cages as a single source precursor

    , SUSTAINABLE ENERGY & FUELS, Vol: 2, Pages: 2674-2686, ISSN: 2398-4902
  • Journal article
    Park MS, Walsh D, Zhang J, Kim JH, Eslava Set al., 2018,

    Efficient hematite photoanodes prepared by hydrochloric acid-treated solutions with amphiphilic graft copolymer

    , JOURNAL OF POWER SOURCES, Vol: 404, Pages: 149-158, ISSN: 0378-7753
  • Journal article
    Poli I, Baker J, McGettrick J, De Rossi F, Eslava S, Watson T, Cameron PJet al., 2018,

    Screen printed carbon CsPbBr3 solar cells with high open-circuit photovoltage

    , JOURNAL OF MATERIALS CHEMISTRY A, Vol: 6, Pages: 18677-18686, ISSN: 2050-7488
  • Journal article
    Zhang J, Garcia-Rodriguez R, Cameron P, Eslava Set al., 2018,

    Role of cobalt-iron (oxy)hydroxide (CoFeOx) as oxygen evolution catalyst on hematite photoanodes

    , Energy and Environmental Science, Vol: 11, Pages: 2972-2984, ISSN: 1754-5692

    Photoelectrochemical solar water splitting into hydrogen and oxygen offers an elegant and potentially efficient way to store solar energy in the chemical bonds of hydrogen, but the oxygen evolution rate is quite limited. The deposition of an oxygen evolution catalyst on the photoanode can enhance oxygen evolution, although the precise interplay between the semiconductor and the catalyst remains poorly understood and unoptimized. In this work, we use a combination of electrochemical approaches, including photoelectrochemical impedance spectroscopy and intensity modulated photocurrent spectroscopy, to unravel the nature of the interactions between different loadings of an electrocatalyst (CoFeOx) and a hematite (α-Fe2O3) semiconductor. A thin layer of CoFeOx mainly reduces surface charge recombination, while an extremely thin layer enhances charge transfer kinetics. Moreover, an interlayer of GaOx modifies the surface state distribution and increases the charge transfer rate even further. These findings point to new opportunities for understanding and manipulating complex photoanodes for oxygen evolution.

  • Journal article
    Poli I, Liang X, Baker R, Eslava S, Cameron PJet al., 2018,

    Enhancing the hydrophobicity of perovskite solar cells using C18 capped CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> nanocrystals

    , Journal of Materials Chemistry C, Vol: 6, Pages: 7149-7156, ISSN: 2050-7534

    © The Royal Society of Chemistry. An important limitation in the commercialisation of perovskite solar cells is lack of stability towards moisture due to fast degradation of the absorber perovskite layer. One approach to improve the stability is effective interface engineering by adding materials that can protect the underlying perovskite film. In this work, we look at the incorporation of C18 capped CH3NH3PbI3 nanocrystals (MAPI NCs) in perovskite solar cells with both standard and inverted architecture. Three different solution-processing techniques were investigated and compared. We show that solar cells with MAPI NCs integrated at the perovskite-Spiro interface can reach over 10% efficiency. The presence of long chain ligands bound to the MAPI NCs does not appear to damage hole extraction. Most importantly, the hydrophobicity of the surface is significantly enhanced, leading to a much higher device stability towards moisture.

  • Journal article
    Walsh D, Patureau P, Robertson K, Reeksting S, Lubben A, Eslava S, Weller MTet al., 2017,

    Exploring effects of intermittent light upon visible light promoted water oxidations

    , SUSTAINABLE ENERGY & FUELS, Vol: 1, Pages: 2101-2109, ISSN: 2398-4902
  • Journal article
    Poli I, Eslava S, Cameron P, 2017,

    Tetrabutylammonium cations for moisture-resistant and semitransparent perovskite solar cells

    , JOURNAL OF MATERIALS CHEMISTRY A, Vol: 5, Pages: 22325-22333, ISSN: 2050-7488
  • Journal article
    Hammond OS, Eslava S, Smith AJ, Zhang J, Edler KJet al., 2017,

    Microwave-assisted deep eutectic-solvothermal preparation of iron oxide nanoparticles for photoelectrochemical solar water splitting

    , JOURNAL OF MATERIALS CHEMISTRY A, Vol: 5, Pages: 16189-16199, ISSN: 2050-7488
  • Journal article
    Olowojoba GB, Kopsidas S, Eslava S, Saiz Gutierrez E, Kinloch AJ, Mattevi C, Garcia Rocha V, Taylor ACet al., 2017,

    A facile way to produce epoxy nanocomposites having excellent thermal conductivity with low contents of reduced graphene oxide

    , Journal of Materials Science, Vol: 52, Pages: 7323-7344, ISSN: 1573-4803

    A well-dispersed phase of exfoliated graphene oxide (GO) nanosheets was initially prepared in water. This was concentrated by centrifugation and was mixed with a liquid epoxy resin. The remaining water was removed by evaporation, leaving a GO dispersion in epoxy resin. A stoichiometric amount of an anhydride curing agent was added to this epoxy-resin mixture containing the GO nanosheets, which was then cured at 90 °C for 1 hour followed by 160 °C for 2 hours. A second thermal treatment step of 200 °C for 30 minutes was then undertaken to reduce further the GO in-situ in the epoxy nanocomposite. An examination of the morphology of such nanocomposites containing reduced graphene oxide (rGO) revealed that a very good dispersion of rGO was achieved throughout the epoxy polymer. Various thermal and mechanical properties of the epoxy nanocomposites were measured and the most noteworthy finding was a remarkable increase in the thermal conductivity when relatively very low contents of rGO were present. For example, a value of 0.25 W/mK was measured at 30 °C for the nanocomposite with merely 0.06 weight percentage (wt%) of rGO present, which represents an increase of ~40% compared with that of the unmodified epoxy polymer. This value represents one of the largest increases in the thermal conductivity per wt% of added rGO yet reported. These observations have been attributed to the excellent dispersion of rGO achieved in these nanocomposites made via this facile production method. The present results show that it is now possible to tune the properties of an epoxy polymer with a simple and viable method of GO addition.

  • Journal article
    Zhang J, Salles I, Pering S, Cameron PJ, Mattia D, Eslava Set al., 2017,

    Nanostructured WO3 photoanodes for efficient water splitting via anodisation in citric acid

    , RSC ADVANCES, Vol: 7, Pages: 35221-35227
  • Journal article
    Eslava S, Reynal A, Rocha VG, Barg S, Saiz Eet al., 2016,

    Using graphene oxide as a sacrificial support of polyoxotitanium clusters to replicate its two-dimensionality on pure titania photocatalysts

    , Journal of Materials Chemistry A, Vol: 4, Pages: 7200-7206, ISSN: 2050-7496

    The nanostructure optimisation of metal oxides is of crucial importance to exploit their qualities in artificial photosynthesis, photovoltaics and heterogeneous catalysis. Therefore, it is necessary to find viable and simple fabrication methods to tune their nanostructure. Here we reveal that graphene oxide flakes, known for their nano- and two-dimensionality, can be used as a sacrificial support to replicate their nano- and two-dimensionality in photocatalytic titania. This is demonstrated in the calcination of Ti16O16(OEt)32 polyoxotitanium clusters together with graphene oxide flakes, which results in pure titania nanoflakes of <10 nm titania nanoparticles in a two-dimensional arrangement. These titania nanoflakes outperform the titania prepared from only Ti16O16(OEt)32 clusters by a factor of forty in the photocatalytic hydrogen production from aqueous methanol suspensions, as well as the benchmark P25 titania by a factor of five. These outcomes reveal the advantage of using polyoxotitanium clusters with graphene oxide and open a new avenue for the exploitation of the vast variety of polyoxometalate clusters as precursors in catalysis and photovoltaics, as well as the use of graphene oxide as a sacrificial support for nanostructure optimisation.

  • Journal article
    D'Elia E, Eslava S, Miranda M, Georgiou TK, Saiz Eet al., 2016,

    Autonomous self-healing structural composites with bio-inspired design

    , Scientific Reports, Vol: 6, ISSN: 2045-2322

    Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks boundtogether using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Herewe show that it is possible exploit this design in order to create self-healing structural composites byusing thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-andmortarstructures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa(three orders of magnitude higher than the interfacial polymer) and fracture energies that are twoorders of magnitude higher than those of the glass bricks. More importantly, these properties can befully recovered after fracture without using external stimuli or delivering healing agents. This approachdemonstrates a very promising route towards the design of strong, ideal self-healing materials able toself-repair repeatedly without degradation or external stimuli.

  • Journal article
    Olowojoba GB, Eslava S, Gutierrez ES, Kinloch AJ, Mattevi C, Rocha VG, Taylor ACet al., 2016,

    In-situ thermally-reduced graphene oxide/epoxy composites: thermal and mechanical properties

    , Applied Nanoscience, Vol: 6, Pages: 1015-1022, ISSN: 2190-5509

    Graphene has excellent mechanical, thermal, optical and electrical properties and this has made it a prime target for use as a filler material in the development of multifunctional polymeric composites. However, several challenges need to be overcome in order to take full advantage of the aforementioned properties of graphene. These include achieving good dispersion and interfacial properties between the graphene filler and the polymeric matrix. In the present work we report the thermal and mechanical properties of reduced graphene oxide/epoxy composites prepared via a facile, scalable and commercially-viable method. Electron micrographs of the composites demonstrate that the reduced graphene oxide (rGO) is well-dispersed throughout the composite. Although no improvements in glass transition temperature, tensile strength, and thermal stability in air of the composites were observed, good improvements in thermal conductivity (about 36%), tensile and storage moduli (more than 13%) were recorded with the addition of 2 wt% of rGO.

  • Patent
    Iacopi F, Eslava S, Kirschhock CEA, Martens JAet al., 2007,

    UV light exposure for functionalization and hydrophobization of pure silica zeolite

    , USA (US2007/0189961), Europe (EP1816104) and Japan (JP2007210884).

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