Stable Silicon Research Articles

Synthesis of Silicon in the Interaction of Aluminum With a Quasi-Neutron and Estimation of the Contribution of the Aluminum Hydride Complex

Among the nuclear fusion reactions of new elements, the simplest reaction refers to the capture of a proton p by the nucleus of the original element ZXA with the formation of the Z + 1YA+1 nucleus (Z and A are the charge and mass number of the element X). In the case of cold fusion, the occurrence of such a reaction is associated with the existence of quasi-neutron (p + e) states in which the proton is “escorted” by the electron e: ZXA + (p + e) ! Z + 1YA+1 + e. For example the synthesis of zinc from copper was established. It is important to note that the ratios of the proportions of synthesized isotopes in most cases should differ significantly from natural ratios, which would certainly confirm their artificial origin. The data of preliminary mass spectrometric measurements for the synthesis of zinc from copper, gallium from zinc, and rhenium from tungsten are consistent with this conclusion. However, for relatively heavy elements, the masses of daughter atoms with Z + 1YA+1 nuclei are difficult to distinguish from the masses of hydride complexes of parent atoms with ZXA nuclei and hydrogen atoms H formed in the course of mass spectrometric measurements. In this regard, the problem of estimating the contributions of daughter atoms and hydride complexes is topical. The solution of this problem was carried out for the case of silicon synthesis from aluminum. In an air environment with water vapor, an electric arc was ignited between an aluminum anode and a tungsten cathode. Aluminum has one stable isotope 13Al27; therefore, the synthesis of only one of the three stable silicon isotopes 14Si28 was expected, which was observed in the mass spectrum of the powder formed on the anode surface (peak at ⇡ 27.977 a.m.u.). The AlH complex corresponds to a peak at ⇡ 27.989 a.m.u. This peak has a height approximately 2.5 times less than the height of the peak for the mass distribution of silicon atoms. Thus, the relatively low intensity for the mass distribution of the AlH complex suggests that it is the isotope ratios of the synthesized daughter nuclei that make the main contributions to the observed isotope mass ratios in the cases of parent atoms having several stable isotopes.

A Boat-Paddle-Like Molecule Binder with Twining-Blocked and Ultrafast Self-Healing Functionalities for Stable Silicon Anodes.

Self-healing binder is a prospective and efficient strategy to alleviate volume expansion of silicon (Si) anodes. However, excellent mechanical strength and healing ability tend to be mutually exclusive, due to enhanced tensile stress limit by twining polymer chains, while inhibiting polymer diffusion rate and inducing healing failure by blocked chains. Herein, inspired by the planning course of boat and paddles, a novel self-healing binder (PVA-4FBA-PEI) is designed and synthesized with mobile parallel structure and twining-blocked characteristics. The boat-like intermediate (4-formylphenyl) boronic acid (4FBA) blocks entanglement of poly(vinyl alcohol) (PVA) and poly(ethyleneimine) (PEI) chains, where two parallel chains as paddles can simultaneously form to ensure rapid diffusion of chains during bond breakage. Remarkably, it endows dynamic synergistic covalent bonds via C═N and B─O─C junctions within 4FBA, providing the binder with an ultrafast self-healing time of merely 2 min. Moreover, the binder integrates superior plasticity and flexibility of each chain, showing a high tensile strength (14.4 MPa) and stretchability (1163%) among state-of-the-art polymer binders, thus significantly improving structural integrity and electrochemical stability of Si anode during cycling. This work proposes a dynamic reversible structure via figurative molecular coordination, affording a rational viewpoint on synergetic functionalities of polymer binders for Si anodes.

Rectifying solid electrolyte interphase structure for stable multi-dimensional silicon anodes

Electrolyte engineering is a promising strategy to stabilize electrode structure. However, the high active material utilization of Si anode accompanied by inevitable huge volume expansion makes higher requirements than regulating Li metal deposition behaviors from dendrite growth. Herein, we rectified the solid electrolyte interphase (SEI) layer on Si surface to maintain the electrode integrity during repeated cycling. In our design, an oligomeric buffer layer (CHO2-/CH3O-) derived from FEC and an inorganic pillar (LiF/Li3N) derived from LiFSI/LiNO3 weave into organic-inorganic crosslinking SEI during the initial activation process. Leveraging COMSOL modeling reveals the small stress and strain of the Si particle under the protective effect of concrete SEI layers. Moreover, synchrotron X-ray 3D nano-computed tomography comprehensively elucidates the structural integrity of Si particles during cycling. With this merit, various silicon-based anodes show remarkable cycling stability. Notably, the Si/C || LiFePO4 full battery still affords a capacity retention ratio exceeding 95 % at 1 mA cm−2 after 300 cycles. This interphase engineering design strategy provided in our work advances the understanding of how to cope with devastating volume variation by leveraging the SEI characteristic perspective.

Stable silicon isotope fractionation reflects the routing of water through a mesoscale hillslope

Concentration - isotope Ratio - Discharge (C-R-Q) relationships offer a promising means of disentangling the underlying hydrologic, geochemical, and ecological factors that produce variations in stream solute chemistry across a variety of critical zone systems. However, natural environments are both temporally and spatially complex, and prevailing interpretations of these C-R-Q patterns remain difficult to validate. Here we employ three replicate artificially constructed hillslopes at the Landscape Evolution Observatory (LEO) in Tucson, Arizona as simplified analogs to natural catchments. LEO allows us to record silicon stable isotope (δ30Si) signatures of fluid discharge under a controlled irrigation schedule in a system devoid of vegetation. This unique meso‑scale experiment enables, for the first time, evaluation of metalloid stable isotope signatures at the scale of natural hillslopes constrained to known fluid transit time distributions (TTDs) and limited to fractionation in association with secondary mineral formation. We report δ30Si in discharge samples collected over three randomized storm events of varying intensity. The data reflect consistent enrichment in the fluid phase between +1.00 and +2.07 ‰ across the three hillslopes, despite highly variable irrigation scenarios, reflecting substantial loss of SiO2 from solution due to secondary mineral precipitation. We compare results from an isotope-enabled Reactive Transport Model (RTM) and the discharge measurements from LEO to constrain the contributions of both characteristic watershed TTDs and fractionation pathways in emergent δ30Si signatures. Our study confirms and expands upon recent work in natural systems attributing intra-site variability in silicon stable isotope signatures to the routing of fluid through catchments.

Stress-Relieving Carboxylated Polythiophene/Single-Walled Carbon Nanotube Conductive Layer for Stable Silicon Microparticle Anodes in Lithium-Ion Batteries.

Stress-relieving and electrically conductive single-walled carbon nanotubes (SWNTs) and conjugated polymer, poly[3-(potassium-4-butanoate)thiophene] (PPBT), wrapped silicon microparticles (Si MPs) have been developed as a composite active material to overcome technical challenges such as intrinsically low electrical conductivity, low initial Coulombic efficiency, and stress-induced fracture due to severe volume changes of Si-based anodes for lithium-ion batteries (LIBs). The PPBT/SWNT protective layer surrounding the surface of the microparticles physically limits volume changes and inhibits continuous solid electrolyte interphase (SEI) layer formation that leads to severe pulverization and capacity loss during cycling, thereby maintaining electrode integrity. PPBT/SWNT-coated Si MP anodes exhibited high initial Coulombic efficiency (85%) and stable capacity retention (0.027% decay per cycle) with a reversible capacity of 1894 mA h g-1 after 300 cycles at a current density of 2 A g-1, 3.3 times higher than pristine Si MP anodes. The stress relaxation and underlying mechanism associated with the incorporation of the PPBT/SWNT layer were interpreted by quasi-deterministic and quantitative stress analyses of SWNTs through in situ Raman spectroscopy. PPBT/SWNT@Si MP anodes can maintain reversible stress recovery and 45% less variation in tensile stress compared with SWNT@Si MP anodes during cycling. The results verify the benefits of stress relaxation via a protective capping layer and present an efficient strategy to achieve long cycle life for Si-based anodes for next-generation LIBs.

Silicon Analogues of Cyclopropyl Radical Derived from a Highly Stable Cyclic Disilene Compound Featuring a Si-Br Bond.

A halogen-substituted cyclic disilene compound, bromocyclotrisilene, Si3Br(Eind)3 (3a), bearing fused-ring bulky Eind (a: R1 = R2 = Et) groups, has been synthesized as an extraordinarily air-stable compound by the reduction of 1,2-dibromodisilene, (Eind)BrSi═SiBr(Eind) (2a), or tribromosilane, (Eind)SiBr3 (1a), with the Mg or Li metal. The X-ray diffraction analysis of 3a showed that the disilene moiety has an almost planar, but slightly trans-bent structure. Even though 3a is quite air-stable both in solutions and in the solid state, its Si-Br bond is reactive under reducing conditions. The further treatment of 3a with the Li metal leads to the formation of room-temperature thermally stable silicon homologues of the cyclopropyl radical, i.e., the cyclotrisilanyl radicals (6a) [6a(syn) and 6a(anti)], via intramolecular C-H bond activation in a transient silicon homologue of the cyclopropenyl radical, i.e., the cyclotrisilenyl radical, [Si3(Eind)3]• (5a). The formation mechanism of 6a from 5a is discussed based on the theoretical calculations. The unique structural and electronic properties of these Si3 three-membered ring species incorporating the Eind groups have been experimentally and theoretically investigated.

Stable novel silicon allotropes in space group P2/m with various band gap structures by high-throughput screening

Silicon is the fundamental material for the semiconductor and microelectronics industries, but controlling the electronic band gap structure of diamond-type silicon remains a huge challenge to adapt to growing applications. Here, we have predicated 23 new silicon allotropes in space group P2/m from 279 possible structures by high-throughput screening accompanied by graph and group theory based on random strategy (RG2) code. The mechanical, electronic and optical properties of these structures were studied in detail. These novel silicon allotropes demonstrate various electronic structures, including metal, direct/quasi direct bandgap structure, and indirect bandgap structures. These new silicon allotropes demonstrate various electronic structures, including metal, direct/quasi direct bandgap structure, and indirect bandgap structures. Besides different electronic bandgap structures, all 23 structures exhibit strong absorption in the visible light region and P2/m-15 demonstrates the excellent mechanical properties (Bulk modulus beyond 80 GPa). Based on their nice stability, good mechanical, electronic and optical properties validated by the ab inito molecular dynamics simulation, phonon spectra and density functional theoretical calculations, these predicted silicon allotropes provide not only ideas for the synthesis of new silicon allotropes but also dawn for expanding the application of semiconductor materials.

Highly stable silicon oxycarbide all-solid-state batteries enabled by machined learning accelerated screening of oxides and sulfides electrolytes

Traditional trial–error approach severely limits and restricts rapid development of high-performance anode and electrolytes materials, searching huge parameters space of various anode-solid electrolyte interfaces in an effective and efficient way is the key issue. Here, a novel computational strategy combining machine learning and first-principles is proposed to achieve efficient high-throughput screening of oxides and sulfides electrolytes for highly stable silicon oxycarbide all-solid-state batteries. First-principles calculations demonstrate significant compact of material type and elemental doping on interfacial compatibility between silicon oxycarbide and various electrolytes. By proposing several novel descriptors including interfacial adhesion and formation energies of frozen system with low computation cost, the amounts of demanded trainings data are significantly reduced. Gradient-boosted regression tree model shows low mean absolute errors of 0.09 and high R2 value of 0.99 for the prediction of interface formation energy, demonstrating ultrahigh accuracy and reliability of the algorithm. The present work discovers a series of uninvestigated stable anode-solid electrolytes interfacial couples for further experimental preparation.

Rigid-flexible mediated Co-polyimide enabling stable silicon anode in lithium-ion batteries

Silicon is considered as a promising electrode materials for the next generation of lithium-ion batteries. However, it’s commercial applications are hindered by significant volume changes. In this study, copolyimide binders with adjustable rigidity and flexibility were synthesized through simple copolymerization. The rigid segments containing adenine groups (p-APA) provide excellent mechanical strength and interface interaction, while flexible segments containing siloxane bonds and alkane chains (DS-NH2) can buffer volume changes through enhanced mobility and topological entanglement of molecular segments. Optimizing the copolymerization ratio helps minimize damage to the silicon electrode structure and stabilizes solid electrolyte interphase (SEI) growth. Compared to the rigid polyimide binders, rigid-flexible coupling strategy improves cycling stability, remaining a capacity of 2170 mAh/g at 2 A/g after 200 cycles and exhibiting stable cycling for over 750 cycles with a capacity limitation of 1500 mAh/g. The high mass loading silicon anodes, micron-sized silicon oxide electrodes and the full cells also exhibit favorable electrochemical performance. This research provides valuable insights for designing high-performance aromatic polymer binders for high energy density lithium-ion batteries.

Clay minerals control silicon isotope variations of fine-grained river sediments: Implication for the trade-off between physical erosion and chemical weathering

Stable silicon (Si) isotopes in fluvial sediments can provide insights into understanding silicate weathering processes on the Earth's surface. However, a lack of comprehensive studies has hindered full understanding of the factors influencing Si isotope fractionation during continental weathering. In this study, through the analysis of Si isotopes in fine-grained sediments from 13 rivers surrounding the South China Sea, significant variation of Si isotopes in bulk detrital sediments (<63 μm) was observed, with δ30Si values ranging from −0.17‰ to −1.09‰. At basin scale, the δ30Si values are influenced by multiple controlling factors such as climatic conditions, lithology, and tectonic settings, which have a close relationship with the content of clay minerals. The characteristics of weathering types and intensities are ultimately reflected in the weathering products, specifically clay minerals. Compiling data across multiple grain sizes from major rivers globally, robust correlations based on clay mineral classification between δ30Si and Al/Si ratio have been observed, which are unaffected by regional and grain-size variations. As the dominant clay mineral group transitions from illite/chlorite to smectite and kaolinite, the degree of Si isotope fractionation increases progressively. This sequence indicates a shift from stronger physical erosion to more intensive chemical weathering, suggesting a transition in the weathering regime from weathering-limited to transport-limited. This study reveals the intrinsic link between Si isotopic compositions and clay mineral assemblages, providing implications for similar stable isotope research and offering a potential indicator for understanding continental weathering processes and their contributions to the global carbon cycle.

Large-Scale Fabrication of Stable Silicon Anode in Air for Sulfide Solid State Batteries via Ionic-Electronic Dual Conductive Binder.

The construction of a continuous ionic/electronic pathway is critical for Si-based sulfide all-solid-state batteries (ASSBs) with the advantages of high-energy density and high-cycle stability. However, a significant impediment arises from the parasitic reaction occurring between the ionic sulfide solid-state electrolyte and electronic carbon additive, posing a formidable challenge. Additionally, the fabrication of electrodes necessitates stringent operational conditions, further limiting practical applicability. Herein, an ionic-electronic dual conductive binder for the fabrication of robust silicon anode under ambient air conditions in the absence of high-cost and air-sensitive sulfide solid-state electrolyte for ASSBs is reported. This binder incorporates in situ reduced silver nanoparticles into a high-strength polymer rich in ether bonds, establishing a conductive pathway for lithium ions and electrons. With the binder-composited Si anode, the half-cell exhibits a remarkable capacity of 1906.9mAhg-1 and stable cycling for 500 cycles at a current density of 2C (4.4mAcm-2) under a low stack pressure of 5MPa. The full cell using Ni0.9Co0.075Mn0.025O2 (NCM90) exhibits a remark cycling stability within 2000 cycles at 5C (8mAcm-2). This work presents an inspired design of functional binders for large-scale manufacture and mild operation in a low-cost way for Si anodes in ASSBs.

Detrital Input Sustains Diatom Production off a Glaciated Arctic Coast

AbstractIn the Arctic and subarctic oceans, the relatively low supply of silicon (compared to other nutrients) can make it limiting for the growth of diatoms, a fundamental building block of the oceanic food web. Glaciers release large quantities of dissolved silicon and dissolvable solid amorphous silica phases into high‐latitude estuaries (fjords), but the role of these glacially‐derived silica phases in sustaining diatom growth in the coastal and open‐water sectors remains unknown. Here we show how stable and radiogenic silicon isotopes can be used together to address this question, using southwest Greenland as a case study. This study finds enhanced levels of detrital (i.e., mineral) amorphous silica, likely glacially‐sourced, sustaining a large portion of diatom growth observed off the coast, revealing how the phytoplankton community can function during high‐meltwater periods.

Optimization of Laser Micro/Nano Processing of Silicon and Quartz

This research paper explores the application of three laser systems, namely the Nd:YAG laser, fiber laser, and CO2 laser, for the micro/nano machining of silicon and quartz materials. The experimental results demonstrate the successful formation of stable silicon nanoparticles with reduced dimensions. Additionally, a quartz sheet was utilized to create a microlens array. The laser microprocessing technique was enhanced through the implementation of design of experiments (DOE) analysis. A Box-Behnken design (BBD) software was employed to conduct 17 tests, investigating the influence of laser parameters on the microprocessing outcomes. The COMSOL software was utilized for theoretical calculations to determine the distribution of surface temperatures and subsurface temperatures of silicon and quartz. The maximum temperatures achieved were approximately 5700 K for silicon and 2630 K for quartz. Numerical optimization using DOE software improved the production of silicon nanoparticles and quartz microlens, producing silicon nanoparticles wavelength peak and absorption peak values of 318.2 nm and 0.39, respectively. Additionally, quartz microlens numerical aperture and surface roughness improved to 0.494 and 4.64 nm, respectively. Due to the precise control offered by the laser micro/nano machining process, the findings of this study hold potential for diverse applications in optoelectronics and biological imaging that can leverage the unique characteristics of silicon nanoparticles and microlens arrays.

A gradient-distributed binder with high energy dissipation for stable silicon anode

Silicon is considered as a promising alternative to traditional graphite anode for lithium-ion batteries. Due to the dramatic volume expansion of silicon anode generated from the insertion of Li+ ions, the binder which can suppress the severe volume change and repeated massive stress impact during cycling is required greatly. Herein, we design a gradient-distributed two-component binder (GE-PAA) to achieve excellent cyclic stability, and reveal the mechanism of high energy dissipative binder stabilized silicon electrodes. The inner layer of the electrode is the polyacrylic acid polymer (PAA) with high Young’s modulus, which is used as the skeleton binder to stabilize the silicon particle interface and the electrode structure. The outer layer is the gel electrolyte polymer (GE) with lower Young’s modulus, which releases the stress generated during the lithiation and de-lithiation process effectively, achieving the high structural stability at the molecular level and silicon particles. Due to the synergistic effect of the gradient binder design, the silicon electrode retains a reversible capacity of 1557.4 mAh g-1 after 200 cycles at the current density of 0.5 C and 1539.2 mAh g-1 at a high rate of 1.8 C. This work provides a novel binder design strategy for Si anode with long cycle stability.

Highly Stable Silicon Anode Enabled by a Water-Soluble Tannic Acid Functionalized Dual-Network Binder.

Silicon (Si), a high-capacity electrode material, is crucial for achieving high-energy-density lithium-ion batteries. However, Si suffers from poor cycling stability due to its significant volume changes during operation. In this work, a tannic acid functionalized aqueous dual-network binder with an intramolecular tannic acid functionalized network has been synthesized, which is composed of covalent-cross-linked polyamide and ionic-cross-linked alginate (Alg(Ni)-PAM-TA), and employed as an advanced binder for stabilizing Si anodes. The resultant Alg(Ni)-PAM-TA binder, incorporating diverse functional groups including amide, carboxylic acid, and dynamic hydrogen bonds, can easily interact with both Si nanoparticles and the Cu foil, thereby facilitating the formation of a highly resilient network characterized by exceptional adhesion strength. Moreover, molecular dynamics (MD) simulations indicate that the Alg(Ni)-PAM-TA network shows an increased intramolecular hydrogen bond number with increasing concentration of TA and a decreased intramolecular hydrogen bond between PAM and Alg as a result of the aggregation behavior of tannic acids themselves. Consequently, the binder significantly enhances the Si electrode's integrity throughout repeated charge/discharge cycles. At a current density of 0.84 A g-1, the Si electrode retains a capacity of 1863.4 mAh g-1 after 200 cycles. This aqueous binder functionalized with the intramolecular network via the incorporation of TA molecules holds great promise for the development of high-energy-density lithium-ion batteries.

Synergistically enhanced LiF–rich protective layer for highly stable silicon anodes

Silicon (Si) is considered as one of the most promising anode materials with an extremely high specific capacity (3579 mAh/g), which is beyond the limit of conventional graphite anodes in lithium (Li) ion batteries (LIBs). However, large volume changes during the lithiation/delithiation process and formation of an unstable solid electrolyte interface (SEI) layer hinder the practical application of Si anodes. To address these issues, constructing a stable protective layer at the interface between anode and electrolyte is a desirable strategy. In this study, a LiF-rich SEI inducing protective layer (LPL) comprising aluminum fluoride (AlF3) and poly(acrylic acid) (PAA) is introduced onto Si anode to construct a stable LiF–rich SEI layer and mitigate the volume changes of the Si anodes during cycling. Owing to the synergetic effects of AlF3 and PAA, a LiF-rich SEI layer with robust physicochemical properties is uniformly formed on the Si anode. As a result, the LPL coated Si (LPL@Si) anodes exhibit outstanding electrochemical properties in Li metal cell tests. In addition, a full-cell prepared with the LPL@Si anode and LiNi0.8Co0.1Mn0.1O2 as a cathode exhibits an excellent cycling performance and mitigated volume changes, demonstrating the potential of this strategy to protect the Si anodes for the development of high-energy–density LIBs.

Atypical Seasonality of the Silicon Cycle in the Yellow River Estuary and Bohai Sea Revealed by Stable Silicon Isotopes

AbstractBiogeochemical Si cycle in coastal areas is of vital importance due to its close link with the carbon cycle. However, the coastal Si cycle has been heavily perturbated by human activities. In this study, we studied the spatiotemporal distribution of biogenic Si (BSi) and dissolved Si (DSi) combined with stable Si isotopes of DSi (δ30SiDSi) in the Yellow River estuary and Bohai Sea, one of the most populated coastal areas in the world. Over an annual cycle, BSi and DSi concentrations varied from 0 to 43.5 μmol L−1 and from 0.3 to 40 μmol L−1, respectively. This was associated with large δ30SiDSi variations from +0.49 ± 0.22‰ (2sd) in spring to +2.92 ± 0.14‰ in winter, which opposed to observations that summer δ30SiDSi values were usually higher than those in winter. This atypical variation could be attributed to the water‐sediment regulation on the Yellow River occurring every early summer, leading to a strong water mixing pattern and suppressing diatom production in summer. This mixing was further prolonged by extreme autumn rainfall on land. The pulse supply of nutrients subsequently enhanced primary productivity from autumn through winter. In spring, the resuspended seafloor sediments were likely an important DSi source with δ30Si values of &lt;−0.5‰. Our findings suggest that natural Si seasonality has been greatly masked by human activities and climate events in the Bohai Sea. Our study serves as a reference of the Si cycle research endeavors worldwide for revealing the overlaying effect of anthropogenic consequences and natural variability.

Synthesis of Nano Silicon Using Lasers

Two lasers of the same wavelength (1.06 μm) and various specifications were employed to synthesize silicon nanoparticles. The experimental data reveal the formation of stable silicon nanoparticles with different features such as UV-vis absorption, photoluminescence spectrum, Raman spectrum, Zeta potential, and SEM morphology. Theoretical simulations using COMSOL software were adopted to estimate the surface temperature distribution at the silicon surface and underneath. It is found that maximum temperatures of about (5700 K) and (4600 K) were generated when a Q-switched laser pulse of (10 ns) and fiber laser pulse of (127 ns) were used, respectively. While the recoil pressure at the silicon surface was (6.5*105 N/m2) and (1*103 N/m2) when Nd:YAG and fiber laser were used respectively. It found that increasing the laser energy for Nd:YAG laser and fiber laser power leads to a blue shift of the absorption spectra while the absorption intensity increases with the number of laser pulses and irradiation time. Raman spectroscopy for the prepared silicon nanoparticles was carried out. The Raman peaks for silicon nanoparticles reveal the formation of amorphous silicon. These peaks were observed at (482) and (475 cm-1) when Nd:YAG and fiber lasers were used to produce those nanoparticles. While the photoluminescence of the prepared silicon nanoparticles exhibits peaks at (457 nm) and (495 nm) for Nd:YAG and fiber lasers. The zeta potential reveals that silicon nanoparticle stability is greater for nanoparticles produced by fiber lasers (27 mv) than those produced by Nd:YAG lasers (17 mv) for three months. The corresponding silicon nanoparticle sizes refer to (3.8 nm) and (6 nm). Potential applications of silicon nanoparticles in optoelectronics and biological imaging can be conducted due to the controllable laser micro/nano machining process.

Recent developments of polymer-based encapsulants and backsheets for stable and high-performance silicon photovoltaic modules: materials nanoarchitectonics and mechanisms

This review offers a detailed look at materials in encapsulation and backsheets for crystalline silicon photovoltaic (c-Si PV) modules, along with recent research advancements for performance enhancement.

Zero-Gap Porous Silicon Membrane Electrodes for Alkaline Electrolysis

Despite only accounting for a fraction of the annual global hydrogen production, commercial application of water electrolysis is expected to grow significantly in line with global climate action goals1. Furthermore, water electrolysis driven by renewable energy is expected to aid in nullifying the intermittency of renewable energy sources such as wind and solar photovoltaics2.Two main types of water electrolysis have found widespread commercial application – alkaline water electrolysis (AWEs) and polymer electrolyte membrane electrolysis (PEMEs). While PEMEs operate at higher current densities and higher efficiencies, they require expensive precious metal catalysts such as Ir-based cathodes and Pt-based anodes3. In addition, PEMEs generally have a shorter lifespan than AWEs4. Therefore, AWEs are better suited for gigawatt-scale deployment5. Furthermore, it has been shown that AWEs with Ni-based catalysts can compete with Ir and Pt-based PEMEs if a dramatic reduction in the thickness of the separator can be achieved6.A key development in AWEs is the adoption of a zero-gap electrode (ZGE) configuration in which the electrodes are pressed directly on the surface of the separator. It is possible to leverage silicon-based lithographic techniques to produce separators with well-defined pore sizes and porosities, which are significantly thinner than commercially available AWE separators. This has been previously demonstrated for photoelectrochemical devices7. Such porous silicon devices typically suffer from the high gas crossover. One method to limit gas crossover is infilling the pores with ionomers. However, due to volumetric expansion in electrolytes, ionomers – such as the commonly used PEME membrane material, Nafion – are not suitable for microfabricated devices8.In this work, we report the fabrication of stable porous silicon separators with metal electrodes in a zero-gap configuration. These porous silicon separators exhibit ionic resistance comparable to Zirfon (the most commonly used AWE separator9) but at an order of magnitude lower porosity. The ordered and well-defined pore structure of the microfabricated separators allows us to study the influence of separator properties such as pore size and porosity on ionic conductivity and gas crossover in cylindrical pores with no interconnections. References International Energy Agency, The Future of Hydrogen, IEA, IEA, Paris, (2021), p. 203 https://www.iea.org/reports/hydrogen.L. M. Pierpoint, Energy Policy, 96, 751–757 (2016).A. S. Gago et al., ECS Trans., 85, 3 (2018).M. David, C. Ocampo-Martínez, and R. Sánchez-Peña, Journal of Energy Storage, 23, 392–403 (2019).M. Schalenbach, Aleksandar R. Zeradjanin, Olga Kasian, Serhiy Cherevko, and Karl J.J. Mayrhofer, Int. J. Electrochem. Sci., 1173–1226 (2018).M. Schalenbach et al., J. Electrochem. Soc., 163, F3197 (2016).W. J. C. Vijselaar et al., Advanced Energy Materials, 9, 1803548 (2019).T. Pichonat and B. Gauthier-Manuel, Fuel Cells, 6, 323–325 (2006).R. Phillips and C. W. Dunnill, RSC Adv., 6, 100643–100651 (2016).