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Through the use of 2,5-dihydroxyterephthalic acid (DOBDC) as both an etching and a doping agent, a surface modified ZIF-8 (denoted as ZIF-8-5%) has been synthesized and used in the eCO2RR, showing a 2.5 times higher partial current and boosted faradaic efficiency.

The adsorption and activation of CO2 on the electrode interface is a prerequisite and key step for electrocatalytic CO2 reduction reaction (eCO2 RR). Regulating the interfacial microenvironment to promote the adsorption and activation of CO2 is thus of great significance to optimize overall conversion efficiency. Herein, a CO2-philic hydroxyl coordinated ZnO (ZnO-OH) catalyst is fabricated, for the first time, via a facile MOF-assisted method. In comparison to the commercial ZnO, the as-prepared ZnO-OH exhibits much higher selectivity toward CO at lower applied potential, reaching a Faradaic efficiency of 85% at -0.95 V versus RHE. To the best of our knowledge, such selectivity is one of the best records in ZnO-based catalysts reported till date. Density functional theory calculations reveal that the coordinated surficial -OH groups are not only favorable to interact with CO2 molecules but also function in synergy to decrease the energy barrier of the rate-determining step and maintain a higher charge density of potential active sites as well as inhibit undesired hydrogen evolution reaction. Our results indicate that engineering the interfacial microenvironment through the introduction of CO2-philic groups is a promising way to achieve the global optimization of eCO2 RR via promoting adsorption and activation of CO2., The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. X.H., T.Z., J.R.M., and J.A. acknowledge funding from the projects (PID2020-116093RB-C42 and -C43), funded by MCIN/AEI/10.13039/501100011033/. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (grant no. SEV-2017-0706). ICN2 and IREC are funded by the CERCA Programme/Generalitat de Catalunya. X.Z. acknowledges funding from FWO project (12ZV320N). X.H. thanks China Scholarship Council for scholarship support (201804910551).

Co-free Li-rich layered oxides are gaining interest as feasible positiveelectrode materials in lithium-ion batteries (LIBs) in terms of energy density, costreduction, and alleviating safety concerns. Unfortunately, their commercialization ishindered by severe structural degradation that occurs during electrochemical operation.The study at hand demonstrates advanced structural engineering of a Li-rich Co-freeoxide with composition Li1.1Ni0.35Mn0.55O2by spray pyrolysis and subsequentcalcination of an aqueous precursor, creating a segregated structure of two distinctlayered phases with space groupsR3??m(rhombohedral) andC2/m(monoclinic). Thisparticular structure was investigated with powder neutron diffraction, high-resolutionanalytical transmission electron microscopy imaging, and electron energy loss spectroscopic characterization. This complex structurecontributes to the high electrochemical stability and good rate capability observed for this compound (160 mAh/g at C/3 and 100mAh/g at 1C).These results provide new insights into the feasibility of developing and commercializing cobalt-free positiveelectrode materials for LIBs The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 1246 and 2017 SGR 327 and the Spanish MINECO project ENE2017-85087-C3 and PID2020- 116093RB-C43 / AEI / 10.13039/501100011033. IREC is funded by the CERCA Programme/Generalitat de Catalunya. IREC also acknowledges additional support from the European Regional Development Funds (ERDF, FEDER). This research was funded by HORIZON 2020-supported EU project COBRA, grant number H2020-EU.3.4.-875568. The authors also acknowledge Stephen Hull and Ron Smith for collecting neutron data at the ISIS neutron and the muon source using rapid access. The experiment number was 2000189.

Lithium-sulfur batteries (LSBs) are still limited by the shuttle of lithium polysulfides (LiPS) and the slow Li-S reaction. Herein, we demonstrate that when using cobalt sulfide as a catalytic additive, an external magnetic field generated by a permanent magnet can significantly improve the LiPS adsorption ability and the Li-S reaction kinetics. More specifically, the results show both experimentally and theoretically how an electron spin polarization of Co ions reduces electron repulsion and enhances the degree of orbital hybridization, thus resulting in LSBs with unprecedented performance and stability. Under an external magnetic field, LSBs with 0.0084 % per cycle decay rate at 2 C during 8150 cycles are produced. Overall, this work not only demonstrates an effective strategy to promote LiPS adsorption and electrochemical conversion in LSBs at no additional energy cost but also enriches the application of the spin effect in the electrocatalysis fields., This work was supported by the National Natural Science Foundation of China (Grant Nos.: 51572118 and 21975123) and partially by the Fundamental Research Funds for the Central Universities (Grant Nos.: lzujbky-2021-it33). C. Y. Zhang, C. Q. Zhang, and L. Gong thank the China Scholarship Council for the scholarship support. A. Cabot thanks financial support from the Combenergy project (PID2019-105490RB-C32) from the Spanish Ministerio de Ciencia e Innovación. The authors also greatly acknowledge the support supported by the Supercomputing Center of Lanzhou University, China., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Tetraaza[14]annulenes (TAA) are synthetic macrocycles which are analogue to porphyrins. However, there are almost no reports about the synthesis of polymers based on TAA and neither on their use as electrocatalysts. The study of new catalysts to promote an efficient electrochemical conversion of carbon dioxide to valuable chemicals is a promising approach to relieve the pressure of carbon emissions and realize the carbon cycle. Herein, we first report the synthesis of a novel tetraaza[14]annulene (TAA) based organic polymeric metal complex (PMC) by a non-template method. This PMC is used as ligand to construct a π-d conjugated cobalt coordination polymer (Poly-TAA-Co) with CoN structure which is supported on multi-wall carbon nanotubes (CNTs) to work as an atomically dispersed efficient electrocatalyst for the CO reduction reaction (CORR). The resulting catalyst (Poly-TAA-Co-CNT) exhibits excellent performance, with a 90% CO faradaic efficiency, a low overpotential (390 mV) and good stability in 0.5 M KHCO aqueous solution. Density functional theory calculations confirmed that the cobalt tetra[14]annulene is an excellent active site for electrocatalytic CORR. This work not only inspires the design of novel TAA based macromolecules, but also paves the way to the development and application of new molecular-based catalysts for electrocatalytic CORR., The present work is supported by the projects SEHTOP, ENE2016-77798-C4-3-R, COMBENERGY (PID2019-105490RB-C32) and NANOGEN (PID2020-116093RB-C43), funded by MCIN/ AEI/10.13039/501100011033/ and by “ERDF A way of making Europe”, by the “European Union”. This study was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and the Government of Catalonia. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and ICN2 and IREC are funded by the CERCA Programme /Generalitat de Catalunya. Part of the present work has been performed in the of the Universitat Autònoma de Barcelona Materials Science PhD program. Z.F Liang acknowledges funding from MINECO SO-FPT PhD grant (SEV-2013-0295-17-1). X. Wang and T. Zhang thank the China Scholarship Council, China, for the scholarship support. W. Tang thanks China Postdoctoral Science Foundation (Nos.2021M691008). Authors acknowledge funding from Generalitat de Catalunya 2017SGR327 and 2017SGR1246. This research was supported by JSPS KAKENHI Grant Numbers JP20K15293 (TY).

The shuttling of soluble lithium polysulfides (LiPS) and the sluggish Li-S conversion kinetics are two main barriers toward the practical application of lithium-sulfur batteries (LSBs). Herein, we propose the addition of copper selenide nanoparticles at the cathode to trap LiPS and accelerate the Li-S reaction kinetics. Using both computational and experimental results, we demonstrate the crystal phase and concentration of copper vacancies to control the electronic structure of the copper selenide, its affinity toward LiPS chemisorption, and its electrical conductivity. The adjustment of the defect density also allows for tuning the electrochemically active sites for the catalytic conversion of polysulfide. The optimized S/Cu1.8Se cathode efficiently promotes and stabilizes the sulfur electrochemistry, thus improving significantly the LSB performance, including an outstanding cyclability over 1000 cycles at 3 C with a capacity fading rate of just 0.029% per cycle, a superb rate capability up to 5 C, and a high areal capacity of 6.07 mAh cm-2 under high sulfur loading. Overall, the present work proposes a crystal phase and defect engineering strategy toward fast and durable sulfur electrochemistry, demonstrating great potential in developing practical LSBs., The authors thank the support from the projects ENE2016-77798-C4-3-R and NANOGEN (PID2020-116093RB-C43), funded by MCIN/AEI/10.13039/501100011033/and by “ERDF A way of making Europe”, by the “European Union”. D.Y., M.L., X.H., and C.Z. thank the China Scholarship Council for the scholarship support. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706). IREC and ICN2 are both funded by the CERCA Program/Generalitat de Catalunya. This project received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 823717-ESTEEM3. Calculations at UT Austin were supported by the Welch Foundation (F-1841) and the Texas Advanced Computing Center. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to the ICREA Academia program.

Photoelectrochemical (PEC) water splitting is a very attractive approach to produce clean hydrogen using abundant natural resources such as solar energy and (sea)water. As its primary step, light absorption controls the available amount of photons for the subsequent processes. Light management in PEC water splitting is essential to obtain high performance and efficiency. Herein, light management strategies via selective material choices and device engineering are comprehensively reviewed from two aspects: (1) improving light trapping ability; and (2) extending light absorption range. From a material design standpoint, morphology control of the photoelectrode components and application of surface-plasmon resonance are priorities. Besides these design priorities, approaches and strategies such as doping, solid–solution formation, and photon up-conversion will be briefly discussed. From a device engineering standpoint, tandem PEC devices are proposed to extend light absorption. The concentration of light is involved as an effective route to regulate the photon flux. In addition to experimental work, simulations of light distribution and absorption in PEC water splitting are examined to provide new device-oriented recommendations. This work features realistic and practical light management approaches for efficient and stable PEC water splitting materials, systems and devices by considering the synergistic effects of light absorption, charge transfer, and surface reactivity.

The Semi-Solid Flow Battery (SSFB) is an interesting energy storage system (ESS) for stationary applications but, in spite of the significant work presented on this technology so far, understanding the chemical and physical factors limiting its electrochemical performance is still blurred by measurements under static conditions rather than under real operando conditions. In this study, we have used Vulcan carbon as a conductive additive to formulate LiNi1/3Co1/3Mn1/3O2 (NCM) based slurries as the catholyte to characterize electrical and electrochemical performances using a 3-electrode flow cell by electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD), respectively. The results are correlated with post-mortem analyses of recovered slurries using Scanning Electron Microscopy (SEM), Raman spectroscopy and Rietveld refinement of the NCM crystal structure. Due to the improved electrochemical cycling stability of the Vulcan-based NCM slurry and cell configuration used for measurements, we have been able to characterize the system in terms of electrical contributions and correlate them with particle degradation as well as detect antisite defect formation on cycling. The electrical stability of the contact resistance and cation mixing are identified as factors limiting the performance of the semi-solid slurry. The latter is frequently reported in porous electrodes for Li-ion batteries but, to our knowledge, it has not been reported for SSFBs to date.

The technical feasibility of synthetic natural gas production from biogenic source was evaluated under industrially relevant conditions. The biogas produced from anaerobic digestion in a waste water treatment plant was considered as renewable carbon dioxide source and renewable hydrogen was produced by alkaline electrolysis (37 kWhe) of tap water. In the present work, the catalytic methanation of biogas, partially upgraded biogas and carbon dioxide released by a membrane upgrading unit was performed through innovative micro-structured heat-exchange reactors. A 2-step methanation process, including gas pre-heating, catalytic reaction and water condensation was implemented. Experimentation revealed that, through this process strategy, the outlet gas mixture (CH4 ≥ 95%, H2 ≤ 5% and CO2 ≤ 2.5%) fulfils the requirements for gas grid injection. It was observed that most reaction occurred in the first reactor (T ≈ 400 °C), while the second reactor (T ≈ 300 °C) was necessary to assure a high methane content. The introduction of methane together with carbon dioxide was found to be positive, namely biogas or partially upgraded biogas instead of pure carbon dioxide. The methanation of biogas reduced the reaction hot-spots and increased the methane content at the outlet. Finally, a proper balance between injection requirements and costs was found at 4–5 bar (g).

Photoelectrochemical (PEC) water splitting has attracted great attention during past decades thanks to the possibility to reduce the production costs of hydrogen or other solar fuels, by doing so in a single step and powered by the largest source of renewable energy: the sun. Despite significant efforts to date, the productivities of stable semiconductor materials in contact with the electrolyte are limited, pushing a growing scientific community towards more complex photoelectrode structures. During the last decade, several groups have focused on the strategy of incorporating state of the art photovoltaic absorber materials (such as silicon, III–V compounds and chalcogenide-based thin films). The stability of these devices in harsh acidic or alkaline electrolytes has become a key issue, pushing transparent, conductive and protective layer research. The present review offers a detailed analysis of PEC devices from metal oxide electrodes forming a semiconductor–liquid junction to protected and catalyst-decorated third generation solar cells adapted into photoelectrodes. It consists of a complete overview of PEC systems, from nanoscale design to full device scheme, with a special focus on disruptive advances enhancing efficiency and stability. Fundamental concepts, fabrication techniques and cell schemes are also discussed, and perspectives and challenges for future research are pointed out.

MXenes have demonstrated high performance as negative electrodes in supercapacitors with aqueous electrolytes due to their high redox capacitance. However, oxidation limits their use under positive potential, requiring asymmetric devices with positive electrodes made of other materials which are usually less capacitive compared to MXenes and therefore limit the device performances. Here, we report the synthesis of two-dimensional molybdenum vanadium carbides (MoxV4 xC3), previously unexplored double transition metal MXenes, by selective etching of aluminum from MoxV4 xAlC3 MAX phase precursors. Unlike the ordered double transition metal MXenes reported previously, MoxV4 xC3 exhibits a Mo-V solid solution in the transition metal layers. We have synthesized and characterized four different compositions of MoxV4 xC3 with x ¼ 1, 1.5, 2, and 2.7. We showed that by changing the Mo : V ratio, the surface terminations (O : F ratio), and electrical and electrochemical properties of the resulting MXenes can be tuned. The Mo2.7V1.3C3 composition showed a remarkable volumetric capacitance (up to 860 F cm 3) and high electrical conductivity (830 S cm 1) at room temperature. Moreover, these solid solution MXenes have demonstrated the ability to operate in a wider range of positive potentials compared to other MXenes. Following this discovery, we coupled a Mo2.7V1.3C3 positive electrode with a well-studied Ti3C2 MXene negative electrode to create an all-MXene supercapacitor, as a proof of concept.

The shuttling behavior and sluggish conversion kinetics of the intermediate lithium polysulfides (LiPS) represent the main obstructions to the practical application of lithium–sulfur batteries (LSBs). Herein, a 1D π–d conjugated metal–organic framework (MOF), Ni-MOF-1D, is presented as an efficient sulfur host to overcome these limitations. Experimental results and density functional theory calculations demonstrate that Ni-MOF-1D is characterized by a remarkable binding strength for trapping soluble LiPS species. Ni-MOF-1D also acts as an effective catalyst for S reduction during the discharge process and LiS oxidation during the charging process. In addition, the delocalization of electrons in the π–d system of Ni-MOF-1D provides a superior electrical conductivity to improve electron transfer. Thus, cathodes based on Ni-MOF-1D enable LSBs with excellent performance, for example, impressive cycling stability with over 82% capacity retention over 1000 cycles at 3 C, superior rate performance of 575 mAh g at 8 C, and a high areal capacity of 6.63 mAh cm under raised sulfur loading of 6.7 mg cm. The strategies and advantages here demonstrated can be extended to a broader range of π–d conjugated MOFs materials, which the authors believe have a high potential as sulfur hosts in LSBs., D.Y., Z.L., and P.T. contributed equally to this work. This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the projects ENE2016-77798-C4-3-R and PID2020-116093RB-C43. D.Y. and C.Z. thank the China Scholarship Council for the scholarship support. M.T. thanks the financial support from the National Natural Science Foundation of China (Grants 21974007 and U1930401). Z.L. acknowledges funding from MINECO SO FPI Ph.D. Grant (SEV-2013-0295-17-1). P.T. acknowledges the Humboldt Research Fellowship. Authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, Grant no. SEV-2017-0706). IREC and ICN2 are both funded by the CERCA Programme/Generalitat de Catalunya. This work was supported by Fundamental Research Funds for the Central Universities (buctrc202112). J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128 and to ICREA Academia program. This project received funding from the European Union's Horizon 2020 Research and Innovation Programme under Grant agreement no. 823717 – ESTEEM3. Part of the present work was performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program.

Funding Information: Funding from the European Comission and Tecnio Spring under the Grant agreement TECSPR18-1-0049 Towards High Energy All Solid State Lithium Batteries (SOLBAT) is gratefully acknowledged. IREC acknowledges support of Generalitat de Catalunya. The authors like to acknowledge the support of Aalto University. Publisher Copyright: © 2022, The Author(s). This paper presents the electrochemical performance and characterization of nano Si electrodes coated with titanicone (TiGL) as an anode for Li ion batteries (LIBs). Atomic layer deposition (ALD) of the metal combined with the molecular layer deposition (MLD) of the organic precursor is used to prepare coated electrodes at different temperatures with improved performance compared to the uncoated Si electrode. Coated electrodes prepared at 150 °C deliver the highest capacity and best current response of 1800 mAh g−1 at 0.1 C and 150 mAh g−1 at 20 C. This represented a substantial improvement compared to the Si baseline which delivers a capacity of 1100 mAh g−1 at 0.1 C but fails to deliver capacity at 20 C. Moreover, the optimized coated electrode shows an outstanding capacity of 1200 mAh g−1 at 1 C for 350 cycles with a capacity retention of 93%. The improved discharge capacity, electrode efficiencies, rate capability and electrochemical stability for the Si-based electrode presented in this manuscript are directly correlated to the optimized TiGL coating layer deposited by the ALD/MLD processes, which enhances lithium kinetics and electronic conductivity as demonstrated by equivalent circuit analysis of low frequency impedance data and conductivity measurements. The coating strategy also stabilizes SEI film formation with better Coulombic efficiencies (CE) and improves long cycling stability by reducing capacity lost.

The shuttling behavior and sluggish conversion kinetics of intermediate lithium polysulfides (LiPS) represent the main obstacles to the practical application of lithium–sulfur batteries (LSBs). Herein, an innovative sulfur host is proposed, based on an iodine-doped bismuth selenide (I-Bi2Se3), able to solve these limitations by immobilizing the LiPS and catalytically activating the redox conversion at the cathode. The synthesis of I-Bi2Se3 nanosheets is detailed here and their morphology, crystal structure, and composition are thoroughly. Density-functional theory and experimental tools are used to demonstrate that I-Bi2Se3 nanosheets are characterized by a proper composition and micro- and nano-structure to facilitate Li+ diffusion and fast electron transportation, and to provide numerous surface sites with strong LiPS adsorbability and extraordinary catalytic activity. Overall, I-Bi2Se3/S electrodes exhibit outstanding initial capacities up to 1500 mAh g−1 at 0.1 C and cycling stability over 1000 cycles, with an average capacity decay rate of only 0.012% per cycle at 1 C. Besides, at a sulfur loading of 5.2 mg cm−2, a high areal capacity of 5.70 mAh cm−2 at 0.1 C is obtained with an electrolyte/sulfur ratio of 12 µL mg−1. This work demonstrated that doping is an effective way to optimize the metal selenide catalysts in LSBs., The authors thank the support from the projects ENE2016-77798-C4-3-R and NANOGEN (PID2020-116093RB-C43), funded by MCIN/ AEI/10.13039/501100011033/ and by “ERDF A way of making Europe”, by the “European Union”. M.L., D.Y., X.H., and C.Z. thank the China Scholarship Council for the scholarship support. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706). IREC and ICN2 are both funded by the CERCA Program/Generalitat de Catalunya. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 823717-ESTEEM3.

Regulating the coordination environment via heteroatoms to break the symmetrical electronic structure of M-N active sites provides a promising route to engineer metal-nitrogen-carbon catalysts for electrochemical CO reduction reaction. However, it remains challenging to realize a site-specific introduction of heteroatoms at atomic level due to their energetically unstable nature. Here, this paper reports a facile route via using an oxygen- and nitrogen-rich metal–organic framework (MOF) (IRMOF-3) as the precursor to construct the Fe-O and Fe-N chelation, simultaneously, resulting in an atomically dispersed axial O-coordinated FeN active site. Compared to the FeN active sites without O coordination, the formed FeN-O sites exhibit much better catalytic performance toward CO, reaching a maximum FE of 95% at −0.50 V versus reversible hydrogen electrode. To the best of the authors’ knowledge, such performance exceeds that of the existing Fe-N-C-based catalysts derived from sole N-rich MOFs. Density functional theory calculations indicate that the axial O-coordination regulates the binding energy of intermediates in the reaction pathways, resulting in a smoother desorption of CO and increased energy for the competitive hydrogen production., T.Z, X.H., and H.L contributed equally to this work. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327. IREC acknowledges Generalitat de Catalunya for financial support M2E 2017 SGR 1246. T.Z., J.R.M., and J.A. thank support from the project NANOGEN (PID2020-116093RB-C43), funded by MCIN/AEI/10.13039/501100011033/. ICN2 was supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706). ICN2 and IREC were funded by the CERCA Programme/Generalitat de Catalunya. This project received funding from the European Union's Horizon research and innovation programme under Grant Agreement No. 823717-ESTEEM3. J.L acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodovska-Curie Grant Agreement No 101030637. X.Z. acknowledges funding from FWO project (12ZV320N). Part of the present work was performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. T.Z. and X.H. thank China Scholarship Council for scholarship support (201706180028, 201804910551).

The shuttle effect and the sluggish reaction kinetics of lithium polysulfide (LiPS) seriously compromise the performance of lithium–sulfur batteries (LSBs). To overcome these limitations and enable the fabrication of robust LSBs, here the use of a Mott–Schottky catalyst based on bimetallic phosphide CoFeP nanocrystals supported on carbon nitride tubular nanostructures as sulfur hosts is proposed. Theoretical calculations and experimental data confirm that CoFeP@CN composites are characterized by a suitable electronic structure and charge rearrangement that allows them to act as a Mott–Schottky catalyst to accelerate LiPS conversion. In addition, the tubular geometry of CoFeP@CN composites facilitates the diffusion of Li ions, accommodates volume change during the reaction, and offers abundant lithiophilic/sulfiphilic sites to effectively trap soluble LiPS. Therefore, S@CoFeP@CN electrodes deliver a superior rate performance of 630 mAh g at 5 C, and remarkable cycling stability with 90.44% capacity retention over 700 cycles. Coin cells with high sulfur loading, 4.1 mg cm, and pouch cells with 0.1 Ah capacities are further produced to validate their superior cycling stability. In addition, it is demonstrated here that CoFeP@CN hosts greatly alleviate the often overlooked issues of low energy efficiency and serious self-discharging in LSBs., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the project ENE2016-77798-C4-3-R, and ENE2017-85087-C3. C.Q.Z., R.F.D., K.X., D.W.Y., T.Z., and X.W. thank the China Scholarship Council for the scholarship support. The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and was funded by the CERCA Programme/Generalitat de Catalunya. J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128 and to ICREA Academia program.

This work is an investigation of the properties of semiconductor materials based on metal oxides, their catalytic properties, and their application as gas sensors, which were shown to exhibit high sensitivity, stability, and selectivity to target gases. The aim of this work is the comparison of gas sensing properties of tin dioxide in the form of individual nanowires and nanopowders obtained by sol–gel synthesis. This comparison is necessary because the traditional synthesis procedures of small particle, metal oxide materials seem to be approaching their limit. Because of this, there is increasing interest in the fabrication of functional materials based on nanowires, i.e., quasi-one-dimensional objects. In this work, nanocrystalline tin dioxide samples with different morphology were synthesized. The gas-transport method was used for the fabrication of well-faceted wire-like crystals with diameters ranging between 15–100 nm. The sol–gel method allowed us to obtain fragile gels from powders with grain sizes of about 5 nm. By means of X-ray photoelectron spectroscopy (XPS) it was proven that the nanowires contain considerably smaller amounts of hydroxy groups compared to the nanopowders. This leads to a decrease in the parasitic sensitivity of the sensing materials to humidity. In addition, we demonstrated that the nanowires are characterized by a nearly single-crystalline structure, ensuring higher stability of the sensor response due to the unlikelihood of sample recrystallization. The results from the ammonia detection experiments showed that the ratio of the sensor response to the surface area exhibits similar values for both the individual nanowire and nanopowders-based sensor materials.

This work describes the design of an electrode with enhanced performance applied to all-vanadium redox flow batteries (VRFBs). This new electrode consists of a structural porous carbon felt decorated with TiO2 rutile nanoparticles, which has been nitrided using ammonolysis at 900 °C. An outstanding charge and mass transfer over the electrode-electrolyte interface was observed as a consequence of the synergetic effect of N- and O-functionalization over carbon felt (CF) and the partial formation of TiN (metallic conductor) phase. Moreover, this material has not only improved in terms of catalysis towards the V3+/V2+ redox reaction (k0 = 1.6 × 10−3 cm s−1), but also inhibited the hydrogen evolution reaction (HER), which is one of the main causes of imbalances that lead to battery failure. This led to an impressive high-power peak output value up to 700 mW cm−2, as well as work at high current density in galvanostatic conditions (i.e. 150 mA cm−2), exhibiting low ohmic losses (overpotential) and great redox single cell reversibility, with a superior energy efficiency of 71%. An inexpensive, earth abundant and scalable synthesis method to boost VRFBs technology based on nitrided CF@TiO2 is presented, being able to overcome certain constrains, and therefore to achieve high energy and power densities.

A multilayered p-type photoabsorber based on kesterite Cu2ZnSnSe4 has been functionalized with inexpensive and easily scalable amorphous MoS2 electrocatalyst by cathodic photoelectrodeposition. The resulting photocathodes with a final composition of Mo/MoSe2/Cu2ZnSnSe4/CdS/ZnO/ITO/MoS2 (where ITO = indium tin oxide) feature one of the highest hydrogen evolution catalytic current densities reported to date at a potential E = 0 V vs. RHE (−18 mA cm−2 in pH 2) under 1 sun illumination. A comparison of the performance of the photoelectrode with an analogous dark electrode with composition ITO/MoS2 allows us to estimate a photovoltage of 430 mV, which is very close to the working voltage of an equivalent photovoltaic cell with open circuit voltage VOC = 464 mV. The photoelectrodes show sustained activity at −10 mA cm−2 above the thermodynamic potential of the H+/H2 redox couple (E = +86 mV vs. RHE in pH 2) for 1 hour without any loss of activity. Prolonged reaction times up to 4 hours show no degradation of the photoabsorber multilayered architecture but a decrease in the thickness of the MoS2 electrocatalytic film due to the mechanical stress caused by the hydrogen bubbles forming on the surface of the electrode. The MoS2 layer is key not only to catalyze the catalytic reaction but also to protect the photoabsorber from the corrosive electrolyte solution. The adhesion of the MoS2 electrocatalytic film on the ITO top layer is critical for the stability during hydrogen evolution catalysis.

Hydrogen, produced by water splitting, has been proposed as one of the main green energy vectors of the future if produced from renewable energy sources. However, to substitute fossil fuels, large amounts of pure water are necessary, scarce in many world regions. In this work, we fabricate efficient and earth-abundant electrodes, study the challenges of using real seawater, and propose an electrode regeneration method to face undesired salt deposition. Ni−Mo−Fe trimetallic electrocatalyst is deposited on non-expensive graphitic carbon felts both for hydrogen (HER) and oxygen evolution reactions (OER) in seawater and alkaline seawater. Cl pitting and the chlorine oxidation reaction are suppressed on these substrates and alkalinized electrolyte. Precipitations on the electrodes, mainly CaCO, originating from seawater-dissolved components have been studied, and a simple regeneration technique is proposed to rapidly dissolve undesired deposited CaCO in acidified seawater. Under alkaline conditions, Ni−Mo−Fe-based catalyst is found to reconfigure, under cathodic bias, into Ni−Mo−Fe alloy with a cubic crystalline structure and Ni : Fe(OH) redeposits whereas, under anodic bias, it is transformed into a follicular Ni:FeOOH structure. High productivities over 300 mA cm and voltages down to 1.59 V@10 mA cm for the overall water splitting reaction have been shown, and electrodes are found stable for over 24 h without decay in alkaline seawater conditions and with energy efficiency higher than 61.5 % which makes seawater splitting promising and economically feasible., Authors from IREC acknowledge Generalitat de Catalunya for financial support through the CERCA Programme. J.R.M. acknowledges Generalitat de Catalunya for financial support through the CERCA Programme, M2E (2017 SGR 1246). IREC and ICN2 also acknowledge additional support by the European Regional Development Funds (ERDF, FEDER) and by MINECO coordinated project ENE2017-85087-C3. ICN2 was supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. ICN2 acknowledges funding from Generalitat de Catalunya SEV-2017-0706). J.L. and X.G. are grateful to projects MICINN/FEDER RTI2018-093996-B−C31 and Generalitat de Catalunya 2017 SGR 128. X.G. is grateful to Generalitat de Catalunya for PhD grant 2017 FI_B 00137. JL is a Serra Húnter fellow and is grateful to ICREA Academia program.

Utilization of the renewable energy sources is one of the main challenges in the state-of-the-art technologies for CO recycling. Here we have taken advantage of the solar light harvesting in the thermocatalytic approach to carbon dioxide methanation. The large-surface-area Ni/CeO catalyst produced by a scalable low-cost method was characterized and tested in the dark and under solar light irradiation conditions. Light-assisted CO conversion experiments as well as in-situ DRIFT spectrometry, performed at different illumination intensities, have revealed a dual effect of the incident photons on the catalytic properties of the two-component Ni/CeO catalyst. On the one hand, absorbed photons induce a localized surface plasmon resonance in the Ni nanoparticles followed by dissipation of the heat to the oxide matrix. On the other hand, the illumination activates the photocatalytic properties of the CeO support, which leads to an increase in the concentration of the intermediates being precursor for methane production. Analysis of the methane production at different temperatures and illumination conditions has shown that the methanation reaction in our case is controlled by a photothermally-activated process. The used approach has allowed us to increase the reaction rate up to 2.4 times and consequently to decrease the power consumption by 20 % under solar illumination, thus replacing the conventional thermal activation of the reaction with a green energy source., This work has been done in the framework of the doctorate programme in Materials Science of the Autonomous University of Barcelona. V. Golovanova has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 754397. Authors acknowledge Generalitat de Catalunya for financial support through the CERCA Programme, M2E (2017 SGR 1246) and the CSC – IT Center for Science, Espoo, Finland for provided resources. IREC also acknowledges additional support by the European Regional Development Funds (ERDF, FEDER) and by MINECO coordinated projects MAT2014-59961-C2, ENE2016-80788-C5-5-R and ENE2017-85087-C3. M. C. Spadaro and J. Arbiol acknowledge funding from Generalitat de Catalunya 2017 SGR 327. ICN2 is supported by the Severo Ochoa programme from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme / Generalitat de Catalunya. M. C. Spadaro has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 754510 (PROBIST) and the Severo Ochoa programme.

Although the Faraday efficiencies (FEs) obtained on most of the Ni based single-atom catalysts (Ni-N-C) are satisfactory (generally >90%) for the electrochemical transfer CO2 to CO, their practical application is still limited by their high overpotentials (>600 mV vs. RHE), which implies a higher energy consumption to drive the CO2 RR. In this work, we have prepared a quasi-double star catalyst composed of nearby Ni and Fe active sites via a simple pyrolysis of Ni and Fe co-doped Zn-based MOFs in order to achieve a high selectivity at a low overpotential during the CO2 RR. Specifically, the optimized Ni/Fe-N-C catalyst shows an exclusive selectivity (a maximum FE(CO) of 98%) at a low overpotential of 390 mV vs. RHE, which is superior to both the single metal counterparts (Ni-N-C and Fe-N-C catalysts) and other state-of-the-art M-N-C catalysts. The DFT results further reveal that regulating the catalytic CO2 RR performance via nearby Ni and Fe active sites can potentially break the activity benchmark of the single metal counterparts because the neighboring Ni and Fe active sites not only function in synergy to decrease the reaction barrier for the formation of COOH∗ and desorption of CO∗ in comparison to their single metal counterparts, but also prevent the undesired hydrogen evolution reaction (HER). This work presents a quasi-double-star catalyst composed of two metal sites for high-efficiency CO2 reduction, which paves the way for the rational design of bimetallic catalysts with separated active sites for other reactions., Authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. T. Z., J. R. M. and J. A. acknowledge funding from the Spanish MINECO project NANOGEN (PID2020-116093RB-C43). ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706). ICN2 and IREC are funded by the CERCA Programme/Generalitat de Catalunya. P. T. acknowledges Humboldt Research Fellowship (Ref 3.5-CHN-1206832-HFST-P) for Postdoctoral Researchers sponsored by the Alexander von Humboldt Foundation. X. Z. acknowledges funding from FWO project (12ZV320N). Part of the present work was performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. T. Z. and X. H. thank China Scholarship Council for scholarship support (201706180028, 201804910551). The authors thank Guillaume Sauthier, Javier Saiz, Yunhui Yang for the XPS spectrum, FTIR, and 1H-NMR tests.

Lithium–sulfur batteries (LSBs) are considered to be one of the most promising next generation energy storage systems due to their high energy density and low material cost. However, there are still some challenges for the commercialization of LSBs, such as the sluggish redox reaction kinetics and the shuttle effect of lithium polysulfides (LiPS). Here a 2D layered organic material, C2N, loaded with atomically dispersed iron as an effective sulfur host in LSBs is reported. X‐ray absorption fine spectroscopy and density functional theory calculations prove the structure of the atomically dispersed Fe/C2N catalyst. As a result, Fe/C2N‐based cathodes demonstrate significantly improved rate performance and long‐term cycling stability. Fe/C2N‐based cathodes display initial capacities up to 1540 mAh g−1 at 0.1 C and 678.7 mAh g−1 at 5 C, while retaining 496.5 mAh g−1 after 2600 cycles at 3 C with a decay rate as low as 0.013% per cycle. Even at a high sulfur loading of 3 mg cm−2, they deliver remarkable specific capacity retention of 587 mAh g−1 after 500 cycles at 1 C. This work provides a rational structural design strategy for the development of high‐performance cathodes based on atomically dispersed catalysts for LSBs., ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV‐2017‐0706) and is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. J.D. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowka‐Curie grant agreement No 665919 (P‐SPHERE) co‐funded by Severo Ochoa Programme. Z.L. acknowledges funding from MINECO SO‐FPT PhD grant (SEV‐2013‐0295‐17‐1). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 823717‐ESTEEM3. The present work is supported by the European Regional Development Funds and by the Spanish MINECO through the projects SEHTOP, ENE2016‐77798‐C4‐3‐R, and ENE2017‐85087‐C3. D.Y., X.W., and C.Z. thank the China Scholarship Council for the scholarship support. P.T. acknowledges Humboldt Research Fellowship for Postdoctoral Researchers sponsored by the Alexander von Humboldt Foundation. J.L. obtained International Postdoctoral Exchange Fellowship Program (Talent‐Introduction program) in 2019 and is grateful for the project (2019M663468) funded by the China Postdoctoral Science Foundation. Authors acknowledge funding from Generalitat de Catalunya 2017SGR327 and 2017SGR1246. J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018‐093996‐B‐C31, GC 2017 SGR 128 and to ICREA Academia program. The authors thank Jessica Padilla, Dr. Albert Llorente Mola, and Dr. Tariq Jawhari support in ICN2, IREC and UB, respectively for the help in additional analyses performed in the samples.

The design of the earth‐abundant, nonprecious, efficient, and stable electrocatalysts for efficient hydrogen evolution reaction (HER) in alkaline media is a hot research topic in the field of renewable energies. A heterostructured system composed of MoSx deposited on NiO nanostructures (MoSx@NiO) as a robust catalyst for water splitting is proposed here. NiO nanosponges are applied as cocatalyst for MoS2 in alkaline media. Both NiO and MoS2@NiO composites are prepared by a hydrothermal method. The NiO nanostructures exhibit sponge‐like morphology and are completely covered by the sheet‐like MoS2. The NiO and MoS2 exhibit cubic and hexagonal phases, respectively. In the MoSx@NiO composite, the HER experiment in 1 m KOH electrolyte results in a low overpotential (406 mV) to produce 10 mA cm−2 current density. The Tafel slope for that case is 43 mV per decade, which is the lowest ever achieved for MoS2‐based electrocatalyst in alkaline media. The catalyst is highly stable for at least 13 h, with no decrease in the current density. This simple, cost‐effective, and environmentally friendly methodology can pave the way for exploitation of MoSx@NiO composite catalysts not only for water splitting, but also for other applications such as lithium ion batteries, and fuel cells., A.V. and Z.H.I. acknowledge Knut and Alice Wallenberg Foundation, the Kempe Foundation, and the LTU Lab fund program for partial funding. J.A. and P.Y.T. acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and JRM 2017 SGR 1246. J.A., P.Y.T., and J.R.M. acknowledge the Spanish MINECO project ENE2017‐85087‐C3. ICN2 acknowledges support from the Severo Ochoa Programme (MINECO, Grant no. SEV‐2013‐0295‐17‐1). ICN2 and IREC are funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work was performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program.

The shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPS) hamper the practical application of lithium–sulfur batteries (LSBs). Toward overcoming these limitations, herein an in situ grown CN@NbSe heterostructure is presented with remarkable specific surface area, as a Li–S catalyst and LiPS absorber. Density functional theory (DFT) calculations and experimental results comprehensively demonstrate that CN@NbSe is characterized by a suitable electronic structure and charge rearrangement that strongly accelerates the LiPS electrocatalytic conversion. In addition, heterostructured CN@NbSe strongly interacts with LiPS species, confining them at the cathode. As a result, LSBs cathodes based on CN@NbSe/S exhibit a high initial capacity of 1545 mAh g at 0.1 C. Even more excitingly, CN@NbSe/S cathodes are characterized by impressive cycling stability with only 0.012% capacity decay per cycle after 2000 cycles at 3 C. Even at a sulfur loading of 5.6 mg cm, a high areal capacity of 5.65 mAh cm is delivered. These results demonstrate that CN@NbSe heterostructures can act as multifunctional polysulfide mediators to chemically adsorb LiPS, accelerate Li-ion diffusion, chemically catalyze LiPS conversion, and lower the energy barrier for LiS precipitation/decomposition, realizing the “adsorption-diffusion-conversion” of polysulfides., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economíay Competitividad through the project SEHTOP, ENE2016- 77798-C4-3-R, and ENE2017-85087-C3. D.Y., C.Z. and M.L. thank the China Scholarship Council for the scholarship support (CSC 201806090276, CSC 201706650011 and CSC 201706890005, respectively). Z.L. acknowledges funding from MINECO SO FPI Ph.D. grant (SEV-2013-0295-17-1). The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to ICREA Academia program. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. M.C.S. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No 754510 (PROBIST). M.B. acknowledges support from SUR Generalitat de Catalunya and the EU Social Fund; project ref. 2020 FI 00103.

CoxNi1–xTiO3 systems evaluated as photo- and electrocatalytic materials for oxygen evolution reaction (OER) from water have been studied. These materials have shown promising properties for this half-reaction both under (unbiased) visible-light photocatalytic approach in the presence of an electron scavenger and as electrocatalysts in dark conditions in basic media. In both situations, Co0.8Ni0.2TiO3 exhibits the best performance and is proved to display high faradaic efficiency. A synergetic effect between Co and Ni is established, improving the physicochemical properties such as surface area and pore size distribution, besides affecting the donor density and the charge carrier separation. At higher Ni content, the materials exhibit behavior more similar to that of NiTiO3, which is a less suitable material for OER than CoTiO3.

Zinc-iodide flow battery (ZIFB) is one of the best potential candidates for future grid-scale energy storage, due to its eye-catching features of benign, high energy density and non-corrosive nature. However major investigations have not done yet on the negative electrode of this battery where the Zn deposition/dissolution mechanism takes place, which may have an impact on the battery performance. Herein, we have reported a comparative study of different carbon-based anodes which are conventional graphite felt, carbon paper and graphite foil. Single-cell charge/discharge performances among these three different anodes depicts that the cell with planar, hydrophilic graphite foil anode is showing the best energy efficiency and the lowest cell resistance among the carbonaceous electrodes. Zinc dissolution process during discharge process seems to be the bottleneck for having a stable cell, which was corroborated by the use of a Zn foil anode that shows excellent efficiencies along the successive cycles.

Atomically dispersed metals maximize the number of catalytic sites and enhance their activity. However, their challenging synthesis and characterization strongly complicates their optimization. Here, the aim is to demonstrate that tuning the electronic environment of atomically dispersed metal catalysts through the modification of their edge coordination is an effective strategy to maximize their performance. This article focuses on optimizing nickel-based electrocatalysts toward alcohol electrooxidation in alkaline solution. A new organic framework with atomically dispersed nickel is first developed. The coordination environment of nickel within this framework is modified through the addition of carbonyl (CO) groups. The authors then demonstrate that such nickel-based organic frameworks, combined with carbon nanotubes, exhibit outstanding catalytic activity and durability toward the oxidation of methanol (CHOH), ethanol (CHCHOH), and benzyl alcohol (CHCHOH); the smaller molecule exhibits higher catalytic performance. These outstanding electrocatalytic activities for alcohol electrooxidation are attributed to the presence of the carbonyl group in the ligand chemical environment, which enhances the adsorption for alcohol, as revealed by density functional theory calculations. The work not only introduces a new atomically dispersed Ni-based catalyst, but also demonstrates a new strategy for designing and engineering high-performance catalysts through the tuning of their chemical environment., ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme /Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. Z.L. acknowledges funding from MINECO SO-FPT Ph.D. grant (SEV-2013-0295-17-1). This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 823717-ESTEEM3. The present work is supported by the European Regional Development Fund and by the Spanish MINECO through the projects ENE2016-77798-C4-3-R, ENE2017-85087-C3, and project NANOGEN (PID2020-116093RB-C43). X.W. and T.Z. thank the China Scholarship Council for the scholarship support. P. Tang acknowledges the Humboldt Research Fellowship. Authors acknowledge funding from Generalitat de Catalunya 2017SGR327 and 2017SGR1246. L.L. acknowledges the support from Natural Sciences and Engineering Research Council of Canada (NSERC, DG RGPIN-2020-06675). J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to ICREA Academia program.

Author(s): Bell, Alexis; Deretzis, Ioannis; Donat, Felix; Gallant, Betar; Lee, Jung-Ho; Morante, Joan Ramon; Ogale, Satishchandra; Risch, Marcel; Simonov, Alexandr; Warren, Emily; Neil, Simon; Darby, Claire

To commercially realize the enormous potential of lithium–sulfur batteries (LSBs) several challenges remain to be overcome. At the cathode, the lithium polysulfide (LiPS) shuttle effect must be inhibited and the redox reaction kinetics need to be substantially promoted. In this direction, this work proposes a cathode material based on a transition-metal selenide (TMSe) as both adsorber and catalyst and a hollow nanoreactor architecture: ZnSe/N-doped hollow carbon (ZnSe/NHC). It is here demonstrated both experimentally and by means of density functional theory that this composite provides three key benefits to the LSBs cathode: (i) A highly effective trapping of LiPS due to the combination of sulfiphilic sites of ZnSe, lithiophilic sites of NHC, and the confinement effect of the cage-based structure; (ii) a redox kinetic improvement in part associated with the multiple adsorption sites that facilitate the Li+ diffusion; and (iii) an easier accommodation of the volume expansion preventing the cathode damage due to the hollow design. As a result, LSB cathodes based on S@ZnSe/NHC are characterized by high initial capacities, superior rate capability, and an excellent stability. Overall, this work not only demonstrates the large potential of TMSe as cathode materials in LSBs but also probes the nanoreactor design to be a highly suitable architecture to enhance cycle stability., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economíay Competitividad through the project SEHTOP, ENE2016-77798-C4-3-R, and ENE2017-85087-C3. D. Yang, C. Zhang, and X. Han thank the China Scholarship Council for the scholarship support. Z. Liang acknowledges funding from a MINECO SO FPI PhD grant (SEV-2013-0295-17-1). J. Li obtained an International Postdoctoral Exchange Fellowship (Talent-Introduction program) in 2019 and is grateful for the project (2019M663468) funded by the China Postdoctoral Science Foundation. The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J. Llorca is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to the ICREA Academia program.

Atom-thin transition metal dichalcogenides (TMDs) have emerged as fascinating materials and key structures for electrocatalysis. So far, their edges, dopant heteroatoms and defects have been intensively explored as active sites for the hydrogen evolution reaction (HER) to split water. However, grain boundaries (GBs), a key type of defects in TMDs, have been overlooked due to their low density and large structural variations. Here, we demonstrate the synthesis of wafer-size atom-thin TMD films with an ultra-high-density of GBs, up to ~1012 cm−2. We propose a climb and drive 0D/2D interaction to explain the underlying growth mechanism. The electrocatalytic activity of the nanograin film is comprehensively examined by micro-electrochemical measurements, showing an excellent hydrogen-evolution performance (onset potential: −25 mV and Tafel slope: 54 mV dec−1), thus indicating an intrinsically high activation of the TMD GBs., Z.L. gratefully acknowledges funding supports from Ministry of Education (MOE) under AcRF Tier 1 (M4011782.070 RG4/17 and M4011993.070 RG7/18), AcRF Tier 2 (2015-T2-2-007, 2016-T2-1-131, 2016-T2-2-153, and 2017-T2-2-136), AcRF Tier 3 (2018-T3-1-002), National Research Foundation – Competitive Research Program (NRF-CRP21-2018-0092), and A*Star QTE programme. P.T., S.M.S., J.R.M., and J.A. acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 1246 and the Spanish MINECO coordinated projects between IREC and ICN2 VALPEC (ENE2017-85087-C2-C3). ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2017-0706). IREC and ICN2 are funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. S.M.S. acknowledges funding from ‘Programa Internacional de Becas “la Caixa”-Severo Ochoa’. J.R.M. recognizes also its affiliation to University of Barcelona. Part of the electron microscopy aspects of this work were supported by the EPSRC (UK), as the SuperSTEM Laboratory is the EPSRC National Research Facility for Advanced Electron Microscopy. Q.J.W. acknowledges the supports from MOE, Singapore grant (MOE2016-T2-2-159, MOE2016-T2-1-128, and MOE Tier 1 RG164/15) and National Research Foundation, Competitive Research Program (NRF-CRP18-2017-02) and NSFC (61704082) as well as Natural Science Foundation of Jiangsu Province (BK20170851). X.W. and B.K.T. gratefully acknowledge funding support from MOE, Singapore (grant no. MOE2015-T2-2-043). H.Z. acknowledges the supports from MOE under AcRF Tier 2 (MOE2015-T2-2-057; MOE2016-T2-2-103; and MOE2017-T2-1-162), AcRF Tier 1 (2016-T1-002-051; 2017-T1-001-150; and 2017-T1-002-119), Agency for Science, Technology and Research (A*STAR) under its AME IRG (Project No. A1783c0009), and NTU under Start-Up Grant (M4081296.070.500000) in Singapore. The authors would like to acknowledge the Facility for Analysis, Characterization, Testing, and Simulation, Nanyang Technological University, Singapore, for their electron microscopy and X-ray facilities. H.Z. also thanks the support from ITC via Hong Kong Branch of National Precious Metals Material Engineering Research Center, and the Start-Up Grant from City University of Hong Kong. Theory and simulations work at Rice university (Z.H., L.W., and B.I.Y.) was supported by the Office of Naval Research grant N00014-18-1-2182.

The development of cheap and efficient catalysts for the oxygen evolution reaction (OER) plays a critical role for sustainable energy conversion and storage. Herein, we report on Mn2O3-based systems supported on nickel foams and functionalized with first-row transition-metal (Fe, Co, Ni) oxide nanoparticles (NPs) as OER electrocatalysts in alkaline media, fabricated by a plasma-assisted process. The remarkable substrate porosity and high Mn2O3 active area, due to the quasi-one-dimensional nano-organization, enabled an efficient ultradispersion of Fe2O3, Co3O4, and NiO NPs into Mn2O3 and an intimate oxide-oxide interfacial contact, enhancing thus charge carrier transport and facilitating reactants and products diffusion. Among the developed systems, Fe2O3-Mn2O3 yielded the highest electrocatalytic activity, corresponding to a low overpotential of ~350 mV at 10 mA × cm-2 and a Tafel slope of 70 mV × dec-1, allowing high current density values. The obtained performances, discussed in relation to the material properties, are superior to almost all the state-of-the-art manganese oxide catalysts and compare favorably with various noble-metal-based systems, paving the way to additional activity improvements via compositional and interfacial engineering.

In the present work the effects of the structure composition in terms of Si/Al ratio and Ce addition in the performances of Ni-based zeolites for CO2 methanation under DBD plasma-assisted catalysis were evaluated. Results were compared with the obtained for a commercial Ni/γ-Al2O3 catalyst and all samples were tested both under thermal and non-thermal DBD plasma conditions. It was found that a higher Si/Al ratio led to better performances not only under thermal but, especially, under plasma conditions, which was attributed to the lower affinity of this sample to water and, thus, to a decrease in the inhibitory role of this compound in Sabatier reaction. Furthermore, the addition of Ce as promoter favoured the dielectric properties of the materials and gave additional sites for CO2 activation leading to much better results than the obtained for a commercial Ni/γ-Al2O3 sample and for the Ni/zeolite, especially under plasma conditions. Indeed, the best zeolite of this work (NiCe/Zeolite) reported a CH4 yield of 75% with a power supply of 25 W while, under the same conditions, the commercial sample and the un-promoted Ni/Zeolite presented just 23% and 15%, CH4 yield, respectively. To our knowledge, this is the first time that a structure-reactivity relationship is attempted with zeolite catalysts under DBD plasma-assisted methanation conditions at atmospheric pressure. These facts also indicate that an important route is being opened, allowing answering to the essential question “what are the important characteristics a catalyst must have to show a better performance under plasma-assisted catalysis?”

Zinc-based hybrid flow batteries are one of the most promising systems for medium- to large-scale energy storage applications, with particular advantages in terms of cost, cell voltage and energy density. Several of these systems are amongst the few flow battery chemistries that have been scaled up and commercialized. The existing zinc-based systems rely on zinc electrodeposition in flowing electrolytes as the negative electrode reaction, which is coupled with organic or inorganic positive active species in either solid, liquid or gaseous phases. These reactions are facilitated with specific cell architectures under certain circumstances. To improve the performance and cycle life of these batteries, this review provides fundamental information on zinc electrodeposition and summarizes recent developments in the relevant flow battery chemistries, along with recent applications. The future challenges and opportunities for this technology are discussed.

Power-to-Gas is a chemical energy storage technology based on converting electrical energy into chemical energy in the form of a certain gas, typically hydrogen or methane. The main advantage of methane, namely synthetic natural gas (SNG), is that in this way the already existing gas infrastructure can be used as transport and storage medium. This article evaluates the economic viability of SNG production from CO2 capture and utilization. As representative examples, California, Ontario, Spain, Sweden, Paraguay, Germany and India electricity markets were considered. At present, the estimated cost of SNG is 70–125 EUR/MWh, from 2 to 7 times higher than fossil natural gas. In a feasible future scenario, the costs can be reduced to 40 EUR/MWh, competing directly with the fossil fuel, especially in countries where it is mainly imported as Germany or Spain. To achieve this goal, further R&D is needed, especially on two key parameters: electrolysis efficiency and methanation capex costs. In any case, the economic viability of SNG is subject to high annual operating hours in order to return the initial investment. Therefore, the SNG process, rather than an intermittent grid storage technology, seems a promising in continuously or seasonal production, having a unique niche market among energy storage technologies.

A facile and cost-effective process to synthesize nanostructured silicon from rice husk-originated silica is introduced. Rice husk was acid-washed and then calcined at various temperatures in the range of 600–900 °C. Nanostructured silicon was obtained through magnesiothermic reduction process of SiO2. Products of the magnesiothermic process, elemental silicon together with magnesia and magnesium silicate, were subjected to leaching to remove the latter two phases. Based on XRD and XRF results, nanometric silica powder obtained after 3 h calcination at 700 °C was selected for further processing. After reduction process, the formation of a three-dimensional silicon skeleton 70–90 nm in thickness with the specific surface area of 53.02 m2/g was confirmed through HRTEM, SEM and BET observations, in agreement with X-ray pattern. The electrical response of the silicon-based electrode was measured to be 0.0023 Ω m, indicating the employed synthesis route as a promising one for electrode fabrication.

Both electronic properties and light absorption are key features in materials engineering to achieve efficient photoelectrodes for water splitting. Adjusting the potential drop inside the nanostructured semiconductor material through modification of the electronic properties is mandatory to drive efficiently the photogenerated charges. In this work, a hydrogen reduction treatment on titanium dioxide rutile nanorod based photoanodes has been performed in order to adjust the donor density to maximize electron–hole separation. Also, incident photon-to-current efficiency (IPCE) measurements and the effect of a light bias have been elucidated, finding relevant differences in low illumination conditions due to nonfilled trap states. A physical model is proposed to show the role of the donor density on the overall performance of the photoanodes under study. The obtained productivity was enhanced by structuring the conductive glass substrates where TiO2 nanorods were grown, resulting in a 20% increase of the phot...