Solar Hydrogen Generation from Ambient Humidity Using Functionalized Porous Photoanodes

Solar hydrogen is a promising sustainable energy vector, and steady progress has been made in the development of photoelectrochemical (PEC) cells. Most research in this field has focused on using acidic or alkaline liquid electrolytes for ionic transfer. However, the performance is limited by (i) scattering of light and blocking of catalytic sites by gas bubbles and (ii) mass transport limitations. An attractive alternative to a liquid water feedstock is to use the water vapor present as humidity in ambient air, which has been demonstrated to mitigate the above problems and can expand the geographical range where these devices can be utilized. Here, we show how the functionalization of porous TiO2 and WO3 photoanodes with solid electrolytes—proton conducting Aquivion and Nafion ionomers—enables the capture of water from ambient air and allows subsequent PEC hydrogen production. The optimization strategy of photoanode functionalization was examined through testing the effect of ionomer loading and the ionomer composition. Optimized functionalized photoanodes operating at 60% relative humidity (RH) and Tcell = 30–70 °C were able to recover up to 90% of the performance obtained at 1.23 V versus reverse hydrogen electrode (RHE) when water is introduced in the liquid phase (i.e., conventional PEC operation). Full performance recovery is achieved at a higher applied potential. In addition, long-term experiments have shown remarkable stability at 60% RH for 64 h of cycling (8 h continuous illumination–8 h dark), demonstrating that the concept can be applicable outdoors.</p

Design, development and orchestration of 5G-ready applications over sliced programmable infrastructure

5G networks design and evolution is considered as a key to support the introduction of digital technologies in economic and societal processes. Towards this direction, vertical industries' needs should be considered as drivers of 5G networks design and development with high priority. In the current manuscript, MATILDA is presented, as a holistic 5G end-to-end services operational framework tackling the overall lifecycle of design, development and orchestration of 5G-ready applications and 5G network services over programmable infrastructure, following a unified programmability model and a set of control abstractions

Pion Valence Structure from Ioffe-Time Parton Pseudodistribution Functions

We present a calculation of the pion valence quark distribution extracted using the formalism of reduced Ioffe-time pseudodistributions or more commonly known as pseudo-PDFs. Our calculation is carried out on two different 2 + 1 flavor QCD ensembles using the isotropic-clover fermion action, with lattice dimensions 243 × 64 and 323 × 96 at the lattice spacing of a = 0.127 fm, and with the quark mass equivalent to a pion mass of mπ ≃ 415 MeV. We incorporate several combinations of smeared-point and smeared-smeared pion source-sink interpolation fields in obtaining the lattice QCD matrix elements using the summation method. After one-loop perturbative matching and combining the pseudodistributions from these two ensembles, we extract the pion valence quark distribution using a phenomenological functional form motivated by the global fits of parton distribution functions. We also calculate the lowest four moments of the pion quark distribution through the “operator product expansion without operator product expansion.” We present a qualitative comparison between our lattice QCD extraction of the pion valence quark distribution with that obtained from global fits and previous lattice QCD calculations

Rational Design of Photoelectrodes for the Fully Integrated Polymer Electrode Membrane–Photoelectrochemical Water-Splitting System: A Case Study of Bismuth Vanadate

Photoelectrochemical (PEC) reactors based on polymer electrolyte membrane (PEM) electrolyzers are an attractive alternative to improve scalability compared to conventional monolithic devices. To introduce narrow band gap photoabsorbers such as BiVO4 in PEM-PEC system requires cost-effective and scalable deposition techniques beyond those previously demonstrated on monolithic FTO-coated glass substrates, followed by the preparation of membrane electrode assemblies. Herein, we address the significant challenges in coating narrow band gap metal-oxides on porous substrates as suitable photoelectrodes for the PEM-PEC configuration. In particular, we demonstrate the deposition and integration of W-doped BiVO4 on porous conductive substrates by a simple, cost-effective, and scalable deposition based on the SILAR (successive ionic layer adsorption and reaction) technique. The resultant W-doped BiVO4 photoanode exhibits a photocurrent density of 2.1 mA·cm–2, @1.23V vs RHE, the highest reported so far for the BiVO4 on any porous substrates. Furthermore, we integrated the BiVO4 on the PEM-PEC reactor to demonstrate the solar hydrogen production from ambient air with humidity as the only water source, retaining 1.55 mA·cm–2, @1.23V vs RHE. The concept provides insights into the features necessary for the successful development of materials suitable for the PEM-PEC tandem configuration reactors and the gas-phase operation of the reactor, which is a promising approach for low-cost, large-scale solar hydrogen production.</p

Gluon helicity from global analysis of experimental data and lattice QCD Ioffe time distributions

We perform a new global analysis of spin-dependent parton distribution functions with the inclusion of Ioffe time pseudo-distributions computed in lattice QCD (LQCD), which are directly sensitive to the gluon helicity distribution, $\Delta g$. These lattice data have an analogous relationship to parton distributions as do experimental cross sections, and can be readily included in global analyses. We focus in particular on the constraining capability of current LQCD data on the sign of $\Delta g$ at intermediate parton momentum fractions $x$, which was recently brought into question by analysis of data in the absence of parton positivity constraints. We find that present LQCD data cannot discriminate between positive and negative $\Delta g$ solutions, although significant changes in the solutions for both the gluon and quark sectors are observed.Comment: 24 pages, 7 figure

Towards High-Precision Parton Distributions from Lattice QCD via Distillation

We apply the Distillation spatial smearing program to the extraction of the unpolarized isovector valence PDF of the nucleon. The improved volume sampling and control of excited-states afforded by distillation leads to a dramatically improved determination of the requisite Ioffe-time Pseudo-distribution (pITD). The impact of higher-twist effects is subsequently explored by extending the Wilson line length present in our non-local operators to one half the spatial extent of the lattice ensemble considered. The valence PDF is extracted by analyzing both the matched Ioffe-time Distribution (ITD), as well as a direct matching of the pITD to the PDF. Through development of a novel prescription to obtain the PDF from the pITD, we establish a concerning deviation of the pITD from the expected DGLAP evolution of the pseudo-PDF. The presence of DGLAP evolution is observed once more following introduction of a discretization term into the PDF extractions. Observance and correction of this discrepancy further highlights the utility of distillation in such structure studies

Symmetrical Exsolution of Rh Nanoparticles in Solid Oxide Cells for Efficient Syngas Production from Greenhouse Gases

Carbon dioxide and steam solid oxide co-electrolysis is a key technology for exploiting renewable electricity to generate syngas feedstock for the Fischer–Tropsch synthesis. The integration of this process with methane partial oxidation in a single cell can eliminate or even reverse the electrical power demands of co-electrolysis, while simultaneously producing syngas at industrially attractive H2/CO ratios. Nevertheless, this system is rather complex and requires catalytically active and coke tolerant electrodes. Here, we report on a low-substitution rhodium-titanate perovskite (La0.43Ca0.37Rh0.06Ti0.94O3) electrode for the process, capable of exsolving high Rh nanoparticle populations, and assembled in a symmetrical solid oxide cell configuration. By introducing dry methane to the anode compartment, the electricity demands are impressively decreased, even allowing syngas and electricity cogeneration. To provide further insight on the Rh nanoparticles role on methane-to-syngas conversion, we adjusted their size and population by altering the reduction temperature of the perovskite. Our results exemplify how the exsolution concept can be employed to efficiently exploit noble metals for activating low-reactivity greenhouse gases in challenging energy-related applications.</p

FeP Nanocatalyst with Preferential [010] Orientation Boosts the Hydrogen Evolution Reaction in Polymer-Electrolyte Membrane Electrolyzer

The development of nonprecious metal electrocatalysts for polymer-electrolyte membrane (PEM) water electrolysis is a milestone for the technology, which currently relies on rare and expensive platinum-group metals. Half-cell measurements have shown iron phosphide materials to be promising alternative hydrogen evolution electrocatalysts, but their realistic performance in flow-through devices remains unexplored. To fill this gap, we report herein the activity and durability of FeP nanocatalyst under application-relevant conditions. Our facile synthesis route proceeds via impregnation of an iron complex on conductive carbon support followed by phosphorization, giving rise to highly crystalline nanoparticles with predominantly exposed [010] facets, which accounts for the high electrocatalytic activity. The performance of FeP gas diffusion electrodes toward hydrogen evolution was examined under application-relevant conditions in a single cell PEM water electrolysis at 22 °C. The FeP cathode exhibited a current density of 0.2 A cm–2 at 2.06 V, corresponding to a difference of merely 0.07 W cm–2 in power input as compared to state-of-the-art Pt cathode, while outperforming other nonprecious cathodes operated at similar temperature. Quantitative product analysis of our PEM device excluded the presence of side reactions and provided strong experimental evidence that our cell operates with 84–100% Faradaic efficiencies and with 4.1 kWh Nm–3 energy consumption. The FeP cathodes exhibited stable performance of over 100 h at constant operation, while their suitability with the intermittency of renewable sources was demonstrated upon 36 h operation at variable power inputs. Overall, the performance as well as our preliminary cost analysis reveal the high potential of FeP for practical applications.</p

Toward the Determination of the Gluon Helicity Distribution in the Nucleon from Lattice Quantum Chromodynamics

We present the first exploratory lattice quantum chromodynamics (QCD) calculation of the polarized gluon Ioffe-time pseudodistribution in the nucleon. The Ioffe-time pseudodistribution provides a frame-independent and gauge-invariant framework to determine the gluon helicity in the nucleon from first principles. We employ a high-statistics computation using a 323 × 64 lattice ensemble characterized by a 358 MeV pion mass and a 0.094 fm lattice spacing. We establish the pseudodistribution approach as a feasible method to address the proton spin puzzle with successive improvements in statistical and systematic uncertainties anticipated in the future. Within the statistical precision of our data, we find a good comparison between the lattice determined polarized gluon Ioffe-time distribution and the corresponding expectations from the state-of-the-art global analyses. We find a hint for a nonzero gluon spin contribution to the proton spin from the model-independent extraction of the gluon helicity pseudodistribution over a range of Ioffe-time, ν ≲ 9