Silica can be converted to silicon by magnesium reduction. Here, this classical reaction is renovated for more efficient preparation of silicon nanoparticles (nano-Si). By reducing the particle size of the starting materials, the reaction can be completed within 10 min by mechanical milling at ambient temperature. The obtained nano-Si with high surface reactivity are directly reacted with 1-pentanol to form an alkoxyl-functionalized hydrophobic colloid, which significantly simplifies the separation process and minimizes the loss of small Si particles. Nano-Si in 5 g scale can be obtained in one single batch with laboratory scale setups with very high yield of 89%. Utilizing the excellent dispersion in ethanol of the alkoxyl-functionalized nano-Si, surface carbon coating can be readily achieved by using ethanol soluble oligomeric phenolic resin as the precursor. The nano-Si after carbon coating exhibit excellent lithium storage performance comparable to the state of the art Si-based anode materials, featured for the high reversible capacity of 1756 mAh·g–1 after 500 cycles at a current density of 2.1 A·g–1. The preparation approach will effectively promote the development of nano-Si-based anode materials for lithium-ion batteries.Keywords: colloidal; lithium-ion batteries; magnesium; silicon nanoparticles; surface functionalization;

•Positive side of the surface alumina: enabling self-assembly of Al nanoparticles and GO into a 3D composite structure.•Negative side of the surface alumina: blocking Li+ transport.•The oxide layer can be removed by thermal etching using anhydrous HCl to vitalize the lithium storage capability of Al.•High lithium storage performance (1041 mAh g−1 after 500 cycles) is achieved for the 3D Al/rGO composite.Aluminum is an attractive anode material for lithium ion batteries due to its low cost, high capacity and low equilibrium potential for lithiation/delithiation. The compact surface oxide layer is usually considered to be detrimental for lithium storage in Al due to its poor conductivity for Li+. Here we show that the Al oxide layer, which is positively charged, can be utilized to assist the homogeneous loading of the Al nanoparticles on to the negatively charged graphene oxide (GO) sheets. During the thermal reduction of GO to reduced GO (rGO), anhydrous HCl is introduced to selectively remove the surface oxide on the Al particles. The vitalized Al/rGO composite exhibits high lithium storage capacity of 1041 mAh g−1 after 500 cycles at current density of 500 mA g−1. The results demonstrate how the double edged surface oxide layer on Al nanoparticles can be manipulated to enable high performance lithium storage in Al, which is illuminating for the application of Al as a high performance, low cost anode material for lithium ion batteries.Download high-res image (191KB)Download full-size image

The hydrogen evolution reaction (HER) during the electrochemical oxidation of borohydride is the major efficiency loss in direct borohydride fuel cells (DBFCs). Here we show that an YH2–Pd thin film electrode, which combines catalysis on the Pd layer and H storage in the YH2 layer, can effectively promote the energy utilization efficiency. The YH2 layer can absorb the atomic H generated during the BH4− oxidation on the Pd layer and effectively suppress HER. The absorbed H can be further oxidized into H2O in NaOH solution, allowing full utilization of the 8 electrons in BH4− oxidation. The YH2–Pd electrode can be regarded as a hybridization of the anodes in conventional DBFCs and nickel-metal hydride batteries. The hydrogen absorption/desorption during the electrochemical process is in situ monitored by optical transmittance measurements, which provide key insights into the interconversion mechanisms and energetics of the hydridic, neutral and protonic hydrogen species.

Fine-tuning of the porphyrin β-periphery is important for naturally occurring metal tetrapyrroles to exert diverse biological roles. Here we describe how this approach is also applied to design molecular catalysts, as exemplified by Ni(II) porphyrinoids catalyzing the hydrogen evolution reaction (HER). We found that β-hydrogenation of porphyrin remarkably enhances the electrocatalytic HER reactivity (turnover frequencies of 6287 vs. 265 s−1 for Ni(II) chlorin (Ni-2) and porphyrin (Ni-1), and of 1737 vs. 342 s−1 for Ni(II) hydroporpholactone (Ni-4) and porpholactone (Ni-3), respectively) using trifluoroacetic acid (TFA) as the proton source. DFT calculations suggested that after two-electron reduction, β-hydrogenation renders more electron density located on the Ni center and thus prefers to generate a highly reactive nickel hydride intermediate. To demonstrate this, decamethylcobaltocene Co(Cp*)2 was used as a chemical reductant. [Ni-2]2− reacts ca. 30 times faster than [Ni-1]2− with TFA, which is in line with the electrocatalysis and computational results. Thus, such subtle structural changes inducing the distinctive reactivity of Ni(II) not only test the fundamental understanding of natural Ni tetrapyrroles but also provide a valuable clue to design metal porphyrinoid catalysts.

A highly efficient noble-metal-free catalyst for the oxygen reduction reaction (ORR) is derived from a composite of polyaniline (PANI) and Prussian blue analogue (PBA, Co3[Fe(CN)6]2) by pyrolysis. The composite consists of 2–5 nm PBA nanocrystals homogeneously dispersed in PANI. During the pyrolysis, the PBA nanocrystals serve as both the template for the pore formation and the precursor for the ORR active sites, which results in a nanoporous structure strongly coupled with the ORR active sites. The catalyst exhibits superior ORR performance in both alkaline and acidic electrolyte, comparable to that of the commercial Pt/C with 20 wt % Pt loading.Keywords: electrocatalysts; oxygen reduction; polyaniline; porous carbon; Prussian blue

In this work we report a highly efficient Co based catalyst for the oxygen reduction reaction (ORR) with highly dispersed Co sites on N-doped carbon. The catalyst is derived from a ZnCo bimetallic metal organic framework (MOF) by heat treatment in an inert atmosphere at 1000 °C. Zn is simultaneously eliminated during the pyrolysis due to its high volatility at high temperature, yielding a highly porous structure with homogeneous Co loading. Another effect of Zn is to disperse Co in the MOF precursor, which effectively inhibits the aggregation of Co after pyrolysis. The best ORR performance is achieved when 5% Zn is substituted by Co in the MOF precursor. The resulting catalyst shows a high half wave potential of 0.90 V vs. reversible hydrogen electrode in 0.1 M KOH solution, which is mainly attributed to the high dispersion of the ORR active Co sites.

•The etherate of LiB3H8 is synthesized via the reaction of Li/Hg and BH3·THF.•The dehydrogenation property of LiB3H8 is investigated.•The process of the synthetic reaction is monitored by NMR spectra.Octahydrotriborates are found to be key intermediates in the dehydrogenation of many borohydrides. In this work, LiB3H8‧1.5THF is synthesized via the reaction between lithium amalgam and BH3‧THF. The structure is confirmed by 11B NMR and FT-IR spectrometry. The synthetic reaction of LiB3H8‧1.5THF is monitored by using 11B NMR. Some boron hydrides, LiB2H7 and LiB4H9, are found to be possible intermediates in this reaction. Thermal dehydrogenation analyses including TPD/MS and TG suggest 6 successive decomposition steps upon heating to 500 °C. The compound emits THF, diborane, pentaborane(9) and hydrogen simultaneously below 170 °C and emits almost pure hydrogen at elevated temperature. LiBH4 is formed at 170 °C as one of the products and disappears at 400 °C. At least two kinds of other intermediates are found in the decomposition reaction, with one of them suspected to be Li2B12H12.

•A highly active and stable Fe-N-C catalyst with uniform atomic iron distribution is derived from ZIF-8.•An O2-free environment for preparing the Fe-doped ZIF-8 precursor is found to be crucial.•The Fe-N-C catalyst exhibited a high half-wave potential (0.82 V vs. RHE) and sufficient stability in acid.•Graphitized carbon in Fe-N-C catalysts is not a necessity for high ORR activity.Compared to extensively studied oxygen reduction reaction (ORR) catalysis in alkaline media, development of highly active and stable nonprecious metal catalysts (NPMCs) to replace Pt in acidic electrolytes remains grand challenges. Among currently studied catalysts, the Fe-N-C formulation holds the greatest promise for the ORR in acid. Here, we report a new highly active and stable Fe-N-C catalyst featured with well-dispersed atomic Fe in porous carbon matrix. It was prepared through one single thermal conversion from Fe-doped ZIF-8, a metal–organic framework (MOF) containing Zn2+ and well-defined Fe–N4 coordination. Unlike other Fe-N-C catalyst preparation, no additional tedious post-treatments such as acid leaching and the second heating treatment are required in this work. Notably, an O2-free environment for preparing the Fe-doped ZIF-8 precursor is found to be crucial for yielding uniform Fe distribution into highly porous N-doped carbon matrix. The resulting new Fe-N-C catalyst exhibited exceptionally improved ORR activity with a very high half-wave potential (0.82 V vs. RHE) and sufficient potential cycling stability in acid. Opposite to previous observation, the highly active Fe-N-C catalyst is in the absence of any graphitized nanocarbons, which would lead to a new discussion in the field for understanding the role of carbon during the ORR electrocatalysis.

Developing noble-metal-free catalysts for electrochemical hydrogen evolution reactions (HER) with superior stability in acid is of critical importance for large-scale, low-cost hydrogen production from water electrolysis. Herein, we report a highly efficient and stable noble-metal-free HER catalyst, which is composed of Ni and Mo2C nanocrystals supported on N-doped graphite nanotubes. This catalyst shows very low overpotential (65 mV in 0.5 M H2SO4 at a current density of 10 mA cm–2 with a Tafel plot of 67 mV/dec) and good stability for HER in acidic electrolyte, which is a promising noble-metal-free HER catalyst.Keywords: graphite nanotube; hydrogen evolution reaction; nitrogen doping; Ni−Mo catalyst; water splitting

Noble metal free electrocatalysts for water splitting are key to low-cost, sustainable hydrogen production. In this work, we demonstrate that metal–organic frameworks (MOFs) can be controllably converted into catalysts for the oxygen evolution reaction (OER) or the hydrogen evolution reaction (HER). The OER catalyst is composed of FeNi alloy nanoparticles encapsulated in N-doped carbon nanotubes, which is obtained by thermal decomposition of a trimetallic (Zn2+, Fe2+, and Ni2+) zeolitic imidazolate framework (ZIF). It reaches 10 mA cm–2 at the overpotential of 300 mV with a low Tafel slope of 47.7 mV dec–1. The HER catalyst consists of Ni nanoparticles coated with a thin layer of N-doped carbon. It is obtained by thermal decomposition of a Ni-MOF in NH3. It shows low overpotential of only 77 mV at 20 mA cm–2 with low Tafel slope of 68 mV dec–1. The above noble metal free OER and HER electrocatalysts are applied in an alkaline electrolyzer driven by a commercial polycrystalline solar cell. It achieves electrolysis efficiency of 64.4% at 65 mA cm–2 under sun irradiation of 50 mW cm–2. This practical application shows the promising prospect of low-cost and high-efficiency sustainable hydrogen production from combination of solar cells with high-performance noble metal free electrocatalysts.Keywords: electrocatalysis; hydrogen evolution; metal−organic frameworks; oxygen evolution; water splitting;

•Excellent catalytic performance for the hydrogen evolution reaction. The biphasic nanocrystalline Ni–Mo–N catalyst shows low overpotential very close to that of commercial Pt/C catalyst and very excellent stability in both acidic and alkaline electrolytes.•Combined merits for catalysis due to unique biphasic structure. The Ni–Mo–N catalyst is composed of homogeneously distributed nanocrystals of metallic Ni and Ni–Mo nitride, which combines the merits of high catalytic activity and good acid stability.The hydrogen evolution reaction (HER) is of critical importance for sustainable hydrogen production from water electrolysis. In this work, we report a highly efficient and stable noble metal free HER catalyst, which is composed of homogeneously distributed metallic Ni and NiMo4N5 nanocrystals. The biphasic nanocrystalline Ni–Mo–N catalyst shows very low overpotential (53 mV in 0.5 M H2SO4 and 43 mV in 1 M KOH, at current density 20 mA/cm2) and good stability for HER in both acidic and alkaline electrolytes, which is a promising low cost alternative for platinum based HER catalysts.

Pyrolysis of a Ni based metal organic framework in NH3 yields Ni nanoparticles with surface nitridation together with thin carbon coating layers. The subtle surface modification significantly improves the catalytic performance for the hydrogen evolution reaction (HER). The surface modified Ni nanoparticles show a low overpotential of only 88 mV at a current density of 20 mA cm−2, which is one of the most efficient HER catalysts based on metallic Ni reported so far. The results suggest that controlled pyrolysis of MOFs is an effective method to prepare highly efficient noble metal free HER catalysts.

Plasma reactions are very effective in the preparation of both silicon and carbon materials. However, Si/C composites, which are highly attractive as the anode material in lithium ion batteries, are difficult to be prepared using plasma due to the strong tendency of silicon carbide (SiC) formation. Here we effectively inhibit the SiC formation by generating reactive Si and C species in separated plasma zones and by using a solid graphite carbon precursor. Homogeneous Si/C nanocomposites with excellent lithium storage performance are obtained by one step plasma deposition at room temperature, which retain a high capacity of 1760 and 1460 mA h g−1 after more than 400 cycles at a charge/discharge rate of 2.0 and 4.0 A g−1, respectively.

A light activated miniature formaldehyde sensor working at room temperature is fabricated by CdSO4 modified ZnO nanoparticles. The CdSO4 is deposited on the surface of the ZnO nanoparticles as a separated phase rather than doping into the lattice of ZnO. The Cd2+ and SO42− on the surface play a synergic effect for the high sensitivity to formaldehyde. The sensor shows high sensitivity to formaldehyde, with detection limit lower than 1 ppm while shows no response to ethanol and very weak response to acetone. With engineering efforts, a highly compact prototype formaldehyde sensor is obtained, which is very convenient for portable formaldehyde specific detection.

ZIF-8 shows complete opposite particle size effects on the adsorption kinetics for two different adsorbates. Smaller ZIF-8 particles favor fast I3− uptake in aqueous solution while larger, less defective ZIF-8 particles exhibit faster adsorption kinetics for gaseous H2, which suggests different adsorption mechanisms for the two adsorbates.

Developing noble metal free catalysts for the oxygen reduction reaction (ORR) is of critical importance for the production of low cost polymer electrolyte membrane fuel cells. In this paper, metal organic frameworks (MOFs) are used as precursors to synthesize ORR catalysts via pyrolysis in an inert atmosphere. The ORR performance is found to be closely associated with the metal/ligand combination in MOFs. The Co-imidazole based MOF (ZIF-67) derived catalyst exhibits the best ORR activity in both alkaline and acidic electrolytes. The Co cations coordinated by the aromatic nitrogen ligands in ZIF-67 may assist the formation of ORR active sites in the derived catalyst. The best ORR performance is obtained when the porosity of the derived catalyst is maximized, by optimizing the pyrolysis temperature and the acid leaching process. The performance of the best MOF derived catalyst is comparable to that of Pt/C in both alkaline and acidic electrolytes.

ZIF-8 nanocrystals with a sub-100 nm size are prepared by a surfactant mediated method in aqueous solution. Pure ZIF-8 phase can be obtained with a stoichiometric Zn/2-methylimidazole ratio. The surfactant mixture of Span 80 and Tween 80 may stabilize the Zn/2-methylimidazole coordination structure and prevent the formation of the hydroxide or alkaline salt. The nanocrystals maintain a high specific surface area of 1360 m2/g. The particle size effect on the adsorption kinetics of the ZIF-8 nanocrystals is studied by using two different probing molecules (I3– anion and Rhodamine B molecule). For the I3– anion, which is smaller than the aperture size of ZIF-8, the ZIF-8 nanoparticles exhibit faster absorption kinetics compared to the bulk material. For the Rhodamine B molecule, which is larger than the aperture size of ZIF-8, only surface adsorption occurs. The enhanced adsorption kinetics of the ZIF-8 nanoparticles is attributed to the smaller particles size, which reduces the intraparticle diffusion length. ZIF-8 nanocrystals prepared by a surfactant mediated method in aqueous solution exhibit faster adsorption kinetics compared to the bulk material.Keywords: aqueous solution; kinetics; nanocrystal; surfactant; ZIF-8

Metal, N codoped nanoporous carbon (N–M–nC, M = Fe, Co) is prepared by in situ incorporation of the metal during the formation of the nanoporous carbon skeleton followed by NH3 treatment. The samples exhibit superior catalytic performance for the oxygen reduction reaction (ORR) in alkaline electrolytes. M, N codoping shows a synergic effect with improved ORR performance compared to the sample with only nitrogen dopant (N–nC), in the order of N–Fe–nC > N–Co–nC > N–nC, indicating that the M–N synergic effect is critical for high ORR performance in alkaline electrolyte. A detailed structural characterization of the catalysts is carried out, which suggests that the improved ORR performance should be attributed to the formation of active sites with M–N bonding. Other structural differences, including surface area, porosity and carbon structure, play a minor role. The performance of the N–Fe–nC sample is comparable to that of commercial Pt/C, including more positive onset and halfwave potential, comparable saturation current density and a dominant four-electron pathway, which suggests that nanoporous carbon can serve as an ideal platform for developing high performance ORR catalysts via proper doping.

•An effective way to enhance the thermal conductivity of microcapsules.•The reduced graphene oxide (rGO) sheets were prepared by different methods.•Low concentration of graphene results in notable increase of thermal conductivity.Reduced graphene oxide (rGO) sheets prepared by different methods are incorporated to boost the thermal conductivity of organic phase change materials (n-eicosane) in silica microcapsules. Low concentration (1 wt%) of graphene dosing already results in notable increase of the thermal conductivity. The preparation methods of rGO significantly affect the thermal properties of the composite. With 1 wt% dosing, sodium borohydride (NaBH4) reduced rGO increases the thermal conductivity by 83% and decrease the phase change enthalpy by 6%. On the other hand, the thermal reduced rGO increases the thermal conductivity by 193% but leads to a 15% loss of the phase enthalpy. The difference is attributed to the different surface morphology and functional groups of the rGO sheets.

Si has a very high theoretical capacity of 4200 mAh g−1 as the anode materials for lithium ion batteries, which is near ten times higher than that of the current commercial graphite anode. However, it suffers from severe volume expansion/contraction during the charge/discharge processes, which is the main obstacle for its application. In this work, we prepare Si/C composite anodes with an intercalated Si/C multilayer structure by alternately depositing C and Si by plasma decomposition of C2H2 and magnetron sputtering of a Si target, respectively. Near theoretical capacity can be achieved (about 4000 mAh g−1) for more than 100 cycles for thin Si layers, which is attributed to the buffer effect of the carbon layers. This structure is also scalable up to multiple Si/C layers. A critical thickness of 20 nm is found for the silicon layer, below which the near theoretical capacity can be stably maintained. This critical thickness may shed light on future designs of nanostructured silicon anode with high capacity and stability for lithium ion batteries.Graphical abstractAn intercalated Si/C multilayer structure was used as the anode for Li-ion batteries. And near theoretical capacity can be achieved (about 4000 mAh g−1) for more than 100 cycles for thin Si layers.Highlights► A new method (novel dual plasma deposition approach) to deposit Si and C together. ► Near theoretical stable capacity can be achieved for Si layer. ► A critical thickness of 20 nm is found for the Si layer.

Silica microcapsules with hierarchical pore structure are prepared using a one step emulsion templated hydrolysis method. Silica particles of around 100 nm with percolated nanosized pores are self-assembled into micrometer scale spherical shells. The porous structure serves as an ideal host for shape stabilization of melted organic compounds. Small angle X-ray scattering (SAXS) results show that the n-eicosane encapsulated in nanoporous silica consists of mass fractal structure with a fractal dimension of 2.1. n-Eicosane encapsulated in the nanosized pores exhibits novel phase change behavior. A large melting point drop from 37.0 to 28.8 °C is observed, which is attributed to the strong interaction between the n-eicosane molecules and the silica skeleton.

•New apporach to prepare Sn/C binary nanocomposites in which particle size of Sn and the content of carbon can be accurately controlled.•The obtained composites exhibits very high reversible capacity (up to 850 mAh g−1 of the Sn component).•A systematic study on the correlation between the electrode performance and the structure parameters (the Sn particle size and the carbon layer thickness).The Sn/C nanocomposites are of great interest as high capacity anode materials for lithium ion batteries (LIBs). In this paper, we employ a tandem plasma reaction method for controlled preparation of Sn/C binary composites. The Sn and C components are generated by magnetron sputtering and plasma decomposition of CH4 in two tandem plasma zones, respectively. The obtained Sn/C composites are composed of ultrafine Sn particles homogeneously embedded in carbon matrix, which exhibit very high reversible lithium storage capacity. The tandem plasma reaction method offers great versatility in controlling the Sn/C ratio and the Sn particle size, allowing a systematic study on the relationship between the structural parameters and the electrode performance. The reversible anode capacity is found to be strongly affected by the Sn particle size while it shows a much weaker correlation with the carbon coating layer.A tandem plasma reaction method enables controlled preparation of Sn/C composites for LIB anode application, allowing a systematic study on the correlation between the reversible capacity and the structural parameters. The results suggest that reducing the Sn particle size is beneficial for attaining high reversible capacity. The carbon layer thickness, on the other hand, shows a much weaker correlation with the reversible capacity.

We prepared a series of nano-sized Mg–Al–Pd trilayer films and investigated their hydrogen storage properties under mild conditions. Results showed that Al 1 nm sample had the best absorption kinetics and excellent optical properties at room temperature, making it a promising candidate for hydrogen sensors and smart windows.

The hydrogen evolution reaction (HER) during the electrochemical oxidation of borohydride is the major efficiency loss in direct borohydride fuel cells (DBFCs). Here we show that an YH2–Pd thin film electrode, which combines catalysis on the Pd layer and H storage in the YH2 layer, can effectively promote the energy utilization efficiency. The YH2 layer can absorb the atomic H generated during the BH4− oxidation on the Pd layer and effectively suppress HER. The absorbed H can be further oxidized into H2O in NaOH solution, allowing full utilization of the 8 electrons in BH4− oxidation. The YH2–Pd electrode can be regarded as a hybridization of the anodes in conventional DBFCs and nickel-metal hydride batteries. The hydrogen absorption/desorption during the electrochemical process is in situ monitored by optical transmittance measurements, which provide key insights into the interconversion mechanisms and energetics of the hydridic, neutral and protonic hydrogen species.

Pyrolysis of a Ni based metal organic framework in NH3 yields Ni nanoparticles with surface nitridation together with thin carbon coating layers. The subtle surface modification significantly improves the catalytic performance for the hydrogen evolution reaction (HER). The surface modified Ni nanoparticles show a low overpotential of only 88 mV at a current density of 20 mA cm−2, which is one of the most efficient HER catalysts based on metallic Ni reported so far. The results suggest that controlled pyrolysis of MOFs is an effective method to prepare highly efficient noble metal free HER catalysts.

Silica microcapsules with hierarchical pore structure are prepared using a one step emulsion templated hydrolysis method. Silica particles of around 100 nm with percolated nanosized pores are self-assembled into micrometer scale spherical shells. The porous structure serves as an ideal host for shape stabilization of melted organic compounds. Small angle X-ray scattering (SAXS) results show that the n-eicosane encapsulated in nanoporous silica consists of mass fractal structure with a fractal dimension of 2.1. n-Eicosane encapsulated in the nanosized pores exhibits novel phase change behavior. A large melting point drop from 37.0 to 28.8 °C is observed, which is attributed to the strong interaction between the n-eicosane molecules and the silica skeleton.

Developing noble metal free catalysts for the oxygen reduction reaction (ORR) is of critical importance for the production of low cost polymer electrolyte membrane fuel cells. In this paper, metal organic frameworks (MOFs) are used as precursors to synthesize ORR catalysts via pyrolysis in an inert atmosphere. The ORR performance is found to be closely associated with the metal/ligand combination in MOFs. The Co-imidazole based MOF (ZIF-67) derived catalyst exhibits the best ORR activity in both alkaline and acidic electrolytes. The Co cations coordinated by the aromatic nitrogen ligands in ZIF-67 may assist the formation of ORR active sites in the derived catalyst. The best ORR performance is obtained when the porosity of the derived catalyst is maximized, by optimizing the pyrolysis temperature and the acid leaching process. The performance of the best MOF derived catalyst is comparable to that of Pt/C in both alkaline and acidic electrolytes.

Plasma reactions are very effective in the preparation of both silicon and carbon materials. However, Si/C composites, which are highly attractive as the anode material in lithium ion batteries, are difficult to be prepared using plasma due to the strong tendency of silicon carbide (SiC) formation. Here we effectively inhibit the SiC formation by generating reactive Si and C species in separated plasma zones and by using a solid graphite carbon precursor. Homogeneous Si/C nanocomposites with excellent lithium storage performance are obtained by one step plasma deposition at room temperature, which retain a high capacity of 1760 and 1460 mA h g−1 after more than 400 cycles at a charge/discharge rate of 2.0 and 4.0 A g−1, respectively.

We prepared a series of nano-sized Mg–Al–Pd trilayer films and investigated their hydrogen storage properties under mild conditions. Results showed that Al 1 nm sample had the best absorption kinetics and excellent optical properties at room temperature, making it a promising candidate for hydrogen sensors and smart windows.