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This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Low Temperature Physics 43, 383 (2017) and may be found at https://doi.org/10.1063/1.4979362 ; The kinetics of the sorption and the subsequent desorption of 4He by the starting graphite oxide (GtO) and the thermally reduced graphene oxide samples (TRGO, Treduction = 200, 300, 500, 700 and 900 °C) have been investigated in the temperature interval 1.5–20 K. The effect of the annealing temperature on the structural characteristics of the samples was examined by the x-ray diffraction (XRD) technique. On lowering the temperature from 20 to 11–12 K, the time of 4He sorption increased for all the samples, which is typically observed under the condition of thermally activated diffusion. Below 5 K the characteristic times of 4He sorption by the GtO and TRGO-200 samples were only weakly dependent on temperature, suggesting the dominance of the tunnel mechanism. In the same region (T < 5 K) the characteristic times of the TRGOs reduced at higher temperatures (300, 500, 700 and 900 °C) were growing with lowering temperature, presumably due to the defects generated in the carbon planes on removing the oxygen functional groups (oFGs). The estimates of the activation energy (Ea) of 4He diffusion show that in the TRGO-200 sample the Ea value is 2.9 times lower as compared to the parent GtO, which is accounted for by GtO exfoliation due to evaporation of the water intercalated in the interlayer space of carbon. The nonmonotonic dependences Ea(T) for the GtO samples treated above 200 °C are determined by a competition between two processes—the recovery of the graphite carbon structure, which increases the activation energy, and the generation of defects, which decreases the activation energy by opening additional surface areas and ways for sorption. The dependence of the activation energy on Treduction correlates well with the contents of the crystalline phase in GtO varying with a rise of the annealing temperature. ; Financial support from Spanish Ministry MINECO and the European Regional Development Fund (Project No. ENE2013-48816-C5-5-R), the Regional Government of Aragon and the European Social Fund DGA-ESF (Project No. T66) and Targeted Comprehensive Fundamental Research Program of NASU (Project No. 6/16-H) is gratefully acknowledged. ; Peer reviewed

5 figures.-- Supporting information available.-- This ACS article is provided under the terms of this ACS AuthorChoice/Editors' Choice via Creative Commons CC-BY agreement: https://pubs.acs.org/page/policy/authorchoice_ccby_termsofuse.html ; Developing highly efficient and stable photoelectrochemical (PEC) water-splitting electrodes via inexpensive, liquid phase processing is one of the key challenges for the conversion of solar energy into hydrogen for sustainable energy production. ZnO represents one the most suitable semiconductor metal oxide alternatives because of its high electron mobility, abundance, and low cost, although its performance is limited by its lack of absorption in the visible spectrum and reduced charge separation and charge transfer efficiency. Here, we present a solution-processed water-splitting photoanode based on Co-doped ZnO nanorods (NRs) coated with a transparent functionalizing metal–organic framework (MOF). The light absorption of the ZnO NRs is engineered toward the visible region by Co-doping, while the MOF significantly improves the stability and charge separation and transfer properties of the NRs. This synergetic combination of doping and nanoscale surface functionalization boosts the current density and functional lifetime of the photoanodes while achieving an unprecedented incident photon to current efficiency (IPCE) of 75% at 350 nm, which is over 2 times that of pristine ZnO. A theoretical model and band structure for the core–shell nanostructure is provided, highlighting how this nanomaterial combination provides an attractive pathway for the design of robust and highly efficient semiconductor-based photoanodes that can be translated to other semiconducting oxide systems. ; A.G.-G., A.K.S., F.M., A.G., D.A.Z., and D.A. acknowledge funding received from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No 722176. W.K.M., A.M.B., and J.H.F. acknowledge financial support from Spanish Ministry MINEICO under Project ENE2016-79282-C5-1-R (AEI/UE/FEDER) and the Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER/UE y DGA T03_20R). ; Peer reviewed

6 Figuras. 3 Tablas. ; The effect of doping on the electronic properties in bulk single-walled carbon nanotube (SWCNT) samples is studied for the first time using a new in situ Raman spectroelectrochemical method, and further verified by DFT calculations and photoresponse. We use p-/n-doped SWCNTs prepared by diazonium reactions as a versatile chemical strategy to control the SWCNT behavior. The measured and calculated data testify an acceptor effect of 4-aminobenzenesulfonic acid (p-doping), and a donor effect (n-doping) in the case of benzyl alcohol. In addition, pristine and covalently functionalized SWCNTs were used for the preparation of photoactive film electrodes. The photocathodic current in the photoelectrochemical cell is consistently modulated by the doping group. These results validate the in situ Raman spectroelectrochemistry as a unique tool box for predicting the electronic properties of functionalized SWCNTs in the form of thin films and their operational functionality in thin film devices for future optoelectronic applications. ; The authors acknowledge financial support from the European Union FP7 RADDEL programme (ITN Marie Curie Actions PEOPLE-2011-290023) and the MEYS Inter Excellence Project no. LTC18039 and H2020-MSCA RISE Agreement no. 734834 (INFUSION). This work at the Instituto de Carboquímica has been funded by the MINECO and the European Regional Development Fund (ENE 2016-79282-C5-1-R), the Government of Aragon (T03-17R), and the European Commission (H2020-MSCA-ITN-2014-ETN 642742 'Enabling Excellence'). The work in Mons is supported by the European Union H2020 iSwitch programme (H2020-MSCA-ITN-2014-ETN 642196). Computational resources in Mons were provided by the Consortium des Équipements de Calcul Intensif (CÉCI) funded by the Belgian National Fund for Scientific Research (F.R.S.-FNRS) under Grant 2.5020.11. J. C. is an FNRS research director. The authors acknowledge the assistance provided by the Research Infrastructures NanoEnviCz (Project No. LM2015073) supported by the Ministry of Education, Youth and Sports of the Czech Republic and the project Pro-NanoEnviCz (Reg. no. CZ.02.1.01/0.0/0.0/16_013/0001821) supported by the Ministry of Education, Youth and Sports of the Czech Republic and the European Union – European Structural and Investments Funds in the frame of Operational Programme Research Development and Education. J. M. G.-D. is grateful to Spanish Ministry of Science, Innovation and Universities for his 'Juan de la Cierva – Incorporación' research grant. A. S. is grateful to Dr Sara Costa and Dr Johan Ek Weis for fruitful discussions and helpful comments. ; We also acknowledge institutional support from the Unit of Information Resources for Research at the "Consejo Superior de Investigaciones Científicas" (CSIC) for the article-processing charges contribution ; Peer reviewed

Carbon nanofoam (CNF) is a highly porous, amorphous carbon nanomaterial that can be produced through the interaction of a high-fluence laser and a carbonbased target material. The morphology and electrical properties of CNF make it an ideal candidate for supercapacitor applications. In this paper, we prepare and characterize CNF supercapacitor electrodes through two different processes, namely, a direct process and a water-transfer process. We elucidate the influence of the production process on the microstructural properties of the CNF, as well as the final electrochemical performance. We show that a change in morphology due to capillary forces doubles the specific capacitance of the wet-transferred CNF electrodes. ; This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 642742. A.M.B., J.H.-F., and W.K.M. acknowledge Spanish MINEICO (project ENE2016-79282-C5-1-R), the Gobierno de Aragón (Grupo Reconocido DGA-T03_17R), and associated EU Regional Development Funds. S.V.-R. thanks Spanish MINEICO for her Ph.D. grant (BES2014-068727 and associated EU Social Funds). ; Peer reviewed

AbstractZinc/air batteries are convenient energy storage devices for both small and massive applications. While future perspectives indicate the need for low‐cost components and sustainable fabrication processes, the battery performance is in part controlled by the kinetics of the oxygen reduction reaction (ORR), which typically involves transition metals as catalysts. In this context, we prepare a series of metal‐free water‐based carbon inks, which are tested for their catalytic performance, once deposited on a gas‐diffusion substrate, in the air cathode of a simple battery prototype. The inks contain a variety of well‐defined carbon nanomaterials and additives, exhibiting different physicochemical properties that critically influence the interaction with the gas diffusion hydrophobic substrate. The intrinsic ORR catalytic activity of the ink material is also analyzed on a glassy carbon electrode by the rotating ring‐disc electrode (RRDE) method and specific capacitance measurements. The discharge capacity on our zinc/air battery prototype correlates well with the intrinsic catalytic activity in the RRDE. However, only the activity in the RRDE does not actually assure the performance on the commercial cathode of the prototype, since other chemical compatibility issues play a role. Thus, we highlight the importance of catalyst testing, not only on the RRDE but also under realistic device conditions.

8 figures.-- Supplementary information available. ; The controlled modification of the electronic properties of ZnO nanorods via transition metal doping is reported. A series of ZnO nanorods were synthesized by chemical bath growth with varying Co content from 0 to 20 atomic % in the growth solution. Optoelectronic behavior was probed using cathodoluminescence, time-resolved luminescence, transient absorbance spectroscopy, and the incident photon-to-current conversion efficiency (IPCE). Analysis indicates the crucial role of surface defects in determining the electronic behavior. Significantly, Co-doping extends the light absorption of the nanorods into the visible region, increases the surface defects, shortens the non-radiative lifetimes, while leaving the radiative lifetime constant. Furthermore, for 1 atomic % Co-doping the IPCE of the ZnO nanorods is enhanced. These results demonstrate that doping can controllably tune the functional electronic properties of ZnO nanorods for applications. ; This work has received funding from the Horizon 2020 program of the European Union for research and innovation, under grant agreement no. 722176 (INDEED) and SNSF via project nr-40B2-0_176680 and BSCGI0-157705. WKM, AMB acknowledge Spanish MINEICO under project ENE2016-79282-C5-1-R (AEI/FEDER, UE) and Gobierno de Aragón (Grupo Reconocido DGAT03_17R (FEDER, UE and T03_20R). ; Peer reviewed

5 Figuras.- Información complementaria disponible en línea en la página web del editor ; Carbon nanofoam (CNF) is a low-density, high-surface-area material formed by aggregation of amorphous carbon nanoparticles into porous nanostructures. We report the use of a pulsed infrared laser to prepare CNF from a graphene oxide (GO) target material. Electron microscopy shows that the films consist of dendritic strings that form web-like three-dimensional structures. The conductivity of these structures can be modified by using the CNF as a nanostructured scaffold for gold nanoparticles deposited by sputter coating, controllably increasing the conductivity by up to 4 orders of magnitude. The ability to measure the conductivity of the porous structures allows electrochemical measurements in the environment. Upon decreasing humidity, the pristine CNF exhibits an increase in resistance with a quick response and recovery time. By contrast, the gold-sputtered CNF showed a decrease in resistance, indicating modification of the doping mechanism due to water adsorption. The sensitivity to humidity is eliminated at the percolation threshold of the metal on the CNF. ; Graham Booth's work is highly appreciated, helping to set up the deposition system. This work has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement 642742 as well as from EU H2020 program "Graphene Flagship" (Grant Agreement 696656). R.A. gratefully acknowledges the support from the Spanish Ministerio de Economia y Competitividad (Grant MAT2016-79776-P, (AEI/FEDER, UE)), from the Government of Aragon and the European Social Fund under the project "Construyendo Europa desde Aragon" 2014–2020 (Grant E/26). A.M.B and W.K.M gratefully acknowledge the financial support from Spanish MINECO and AEI (Project ENE2016-79282-C5-1-R and associated EU Regional Development Funds) and the Gobierno de Aragón (Consolidated Group DGA-T66-GCNN and associated EU Social Funds). S.V.-R. thanks Spanish MINECO for her Ph.D. grant (BES2014-068727 and associated EU Social Funds). ; Peer reviewed

5 Figuras.- Información complementaria disponible en línea en la página web del editor ; Carbon nanofoam (CNF) is a low-density, high-surface-area material formed by aggregation of amorphous carbon nanoparticles into porous nanostructures. We report the use of a pulsed infrared laser to prepare CNF from a graphene oxide (GO) target material. Electron microscopy shows that the films consist of dendritic strings which form web-like three-dimensional structures. The conductivity of these structures can be modified by using the CNF as a nanostructured scaffold for gold nanoparticles deposited by sputter coating, controllably increasing the conductivity by up to four orders of magnitude. The ability to measure the conductivity of the porous structures allows electrochemical measurements in the environment. Upon decreasing humidity, the pristine CNF exhibits an increase in resistance with a quick response and recovery time. By contrast, the gold-sputtered CNF showed a decrease in resistance, indicating modification of the doping mechanism due to water adsorption. The sensitivity to humidity is eliminated at the percolation threshold of the metal on the CNF. ; Graham Booth's work is highly appreciated helping to set up the deposition system. This work has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 642742 as well as for EU H2020 program "Graphene Flagship" (Grant Agreement 696656). R.A. gratefully acknowledges the support from the Spanish Ministerio de Economia y Competitividad (MAT2016-79776-P, (AEI/FEDER, UE)), from the Government of Aragon and the European Social Fund under the project "Construyendo Europa desde Aragon" 2014-2020 (grant number E/26). A.M.B and W.K.M gratefully acknowledge the financial support from Spanish MINECO and AEI (project ENE2016-79282-C5-1-R and associated EU Regional Development Funds), and the Gobierno de Aragón (Consolidated Group DGA-T66-GCNN and associated EU Social Funds). SVR thanks Spanish MINECO for her PhD grant (BES2014-068727 and associated EU Social Funds). ; Peer reviewed