Direct ammonia fuel cells (DAFCs) hold great promise as clean energy conversion devices due to their carbon-free exhaust, the high energy density and liquid-phase storability of ammonia, and use of an existing production and distribution infrastructure. When using the state-of-the-art anion exchange membranes, ammonia crossover from the cathode to the anode can cause rapid decay in DAFC performance as the current density increases. Mixed-metal oxides containing manganese-nickel-cobalt have emerged as NH3-tolerant cathode catalysts, but their systematic testing under variable loading conditions in DAFC is rarely reported. Here, we examine low-temperature DAFCs with electrodeposited platinum (Pt), manganese-cobalt oxide (MnCoOX), and manganese-nickel-cobalt oxide (MnNiCoOX) cathodes on Ni foam. To isolate cathodic effects, all cells use identical Pt on Ni Foam anodes with alkaline ammonia feeds. Structural characterization confirms defect-rich spinel coatings. MnCoOX achieves oxygen reduction reaction performance comparable to Pt, sustaining higher load voltage with lower interfacial resistance and larger capacitance, while MnNiCoOX shows restricted performance and rapid voltage loss, indicating sluggish charge transfer and fewer active sites. These results identify electrodeposited MnCoOX on Ni foam as a promising, scalable platinum group metal-free cathode for DAFCs and highlight compositional and mesostructural tuning as key levers to improve catalytic activity and device performance.

ABSTRACT Nickel‐iron layered double hydroxides (NiFe‐LDH) show excellent activity, their poor conductivity limits practical implementation in electrolysers. Previous reports have shown that combining nickel‐iron layered double hydroxide (NiFe‐LDH) materials with MXenes significantly increases the oxygen evolution reaction (OER) activity, however, the rationale behind this is not clear. Herein, we report operando X‐ray absorption spectroscopy (XAS) of V 2 CT x MXene‐enhanced NiFe‐LDH catalysts, revealing important insights into MXene‐hydroxide synergy. Operando X‐ray absorption reveals a two‐step vanadium transformation: V 2 CT x initially oxidizes during hydrothermal synthesis, acting as a reducing agent that promotes ordered Fe 2 NiO 4 formation, then undergoes further oxidation under OER conditions, to form mixed‐valence V 3+ / 4+ / 5+ oxide species that establish transient electronic coupling with NiFe active sites. Finally, the NiFe@V 2 CT x composites were tested in an Anion Exchange Membrane (AEM) electrolyzer over 144 h of continuous operation at 500 and 1000 mA cm −2 , with NF25 achieving degradation rates as low as 0.76 mV h −1 at 1000 mA cm −2 . Postmortem tests reveal that V 2 CT x undergoes progressive dissolution during operation, yet the structurally modified NiFe electrodes retain superior activity relative to the unmodified reference throughout the full test duration. These findings demonstrate that V 2 CT x functions beyond passive conductive support as an active electronic participant whose structural legacy sustains durable performance even after vanadium leaching.

Abstract Two-dimensional MXenes have emerged as promising support materials for electrocatalysts due to their high electrical conductivity and tunable surface chemistry. This study introduces a hydrothermal synthesis approach using NH4F as an additive to fabricate CoFe@V2CTx composites with systematically varied vanadium content. The NH4F-mediated hydrothermal method redirected crystallization from large catalytically inert crystals toward interfacially nucleated CoFOH and FeOOH phases at the V2CTx surface, reaching maximum abundance in the catalytically optimal composition CFV17. CFV17 demonstrated a reduced overpotential of 304 mV at 10 mA cm−2, a reduction in charge transfer resistance, and the lowest Tafel slope in the series. Operando X-ray absorption spectroscopy at the Co and Fe K-edges confirmed that CFV17 achieved cobalt and iron oxidation states exceeding their Co3+ and Fe3+ references at 150 mV lower potential compared to pure CoFe, mechanistically justifying the enhanced OER activity. Post-stability ICP-OES analysis confirmed that V2CTx stabilizes the CoFe active phase against dissolution. This work establishes V–O–Fe interfacial coordination as the central mechanistic principle leading to OER enhancement in CoFe@V2CTx composites and demonstrates that the NH4F hydrothermal synthesis route enables the compositional and interfacial control required to maximize this effect.

Anion Exchange Membrane (AEM) electrolysers are currently classed as a lower technological readiness level for green H2 production compared to maturer H2 technologies such as proton exchange membrane and solid oxide electrolysers. This is due to a multitude of reasons including catalyst performance. To overcome this, new catalyst configurations must be understood and compared to the relevant industrial route, i.e., powder deposition and materials, i.e., nickel based. Herein, we report the advantages of thin film Ni magnetron sputtered catalysts for green H2 production compared to commercially available NiO powder as a catalyst. The thin film catalysts show significantly improved performances in both a conventional three electrode setup and in an AEM device. Our results indicate that the thin films maintain exceptional structural stability, with near-edge X-ray absorption fine structure (NEXAFS) showing electronic activation primarily through surface sites without significant bulk structural reorganisation, as confirmed by extended X-ray absorption fine structure (EXAFS). In contrast, powder NiO catalysts display strong structural-electronic coupling with progressive structural changes paralleling NEXAFS evolution. In the zero-gap AEM electrolyser, Distribution of Relaxation Times (DRT) analysis further demonstrates that the bottleneck reaction is the oxygen evolution reaction with thin-film NiO exhibiting lower charge transfer resistance than powder NiO.

Ti2CTx is a structurally simple yet chemically fragile MXene whose practical use is limited by rapid and poorly understood oxidation and strong sensitivity to synthesis route, flake thickness, and surface chemistry. Here, we characterize the oxidation behavior of Ti2CTx synthesized via conventional chemical etching (Ch-) and fluoride-free molten salt-shielded synthesis (MS3-) routes by combining X-ray absorption spectroscopy (XAS), scanning X-ray microscopy (SXM), and micro-imaging spectroscopic ellipsometry (mu ISE). XAS and SXM reveal a higher and spatially heterogeneous Ti oxidation state in MS3-Ti2CTx, while Ch-Ti2CTx exhibits a more uniform and reduced Ti state. mu ISE allows mu m-resolved quantitative extraction of optical constants from individual flakes, indicating a high flake thickness dependence of UV-Vis resonances and conductivity, with thicker flakes showing increased metallicity and stability in Ch-Ti2CTx. Ellipsometry also demonstrates that ultrathin flakes undergo rapid oxidation-driven electronic degradation within days, while thicker flakes maintain their optical and electrical properties over extended periods of several weeks. Together, these results establish a framework linking surface chemistry, oxidation heterogeneity, and flake thickness-dependent electronic and optical properties, providing guidance for improving their durability in applications such as nanoelectronics, energy storage, and sensing.

Two pairs of enantiomers were designed, synthesized, and characterized. They differ by the absence or presence of two unpaired electrons, enabling us to probe the role that close- versus open-shell electronic structures play on chiroptical properties and the chiral-induced spin selectivity (CISS) effect. The enantiomers showed comparable high purity and an enantiomeric excess of >99%, enabling accurate physical studies. Specifically, circular dichroism in solution and gold-coated thin films and the chiral-induced anomalous Hall effect were measured and discussed in the light of the molecular structure. The biradical enantiomers showed a magnified CISS effect in spectroscopic and electric measurements versus that of the close-shell enantiomers.

Platinum on carbon remains the proton exchange membrane fuel cell cathode state of the art catalyst, however durability losses tied to support corrosion and Pt coarsening hinders this catalyst. This study investigates into utilizing different variations of Vulcan XC-72 and Ti3C2 MXene to improve oxygen-reduction ORR activity and stability. The materials characterization results provide in depth knowledge of the Pt, carbon and MXene composites. The X-ray photoelectron spectroscopy of the synthesized samples shows that the Ti3C2Tx has oxidized, and the high-resolution transmission electron microscopy further reveals that the Pt (111) fringes are present with local anatase TiO2 on the Ti3C2 MXene, which is also confirmed by Xray microscopy. Rotating disk electrode shows Pt kinetics (~60 mV/dec) and ranks activity as similar Pt/75%C+25%Ti3C2 and Pt/C, followed by Pt/50%C+50%Ti3C2 and then the Ti3C2-rich samples. GDE testing confirms the hierarchy at 1 A/cm2 (75%C+25%Ti3C2 > Pt/C Pt/50%C+50%Ti3C2). Furthermore, galvanostatic electrochemical impedance spectroscopy indicates the lowest charge-transfer/transport losses for Pt/75%C+25%Ti3C2. After a DoE derived accelerated stress test, the Pt/75%C+25%Ti3C2 our performs the Pt/C. TEM size histograms and Raman D/G shifts reveals that a Ti3C2 fraction strengthens metal-support interactions and mitigates Pt growth while preserving percolation and gas pathways. The Pt/75%C+25%Ti3C2 composite defines a practical composition window and a reproducible half-cell protocol for Pt/C+MXene screening. This study is the first coupled cathode half-cell performance and potential-cycling durability testing for MXene derived composites benchmarked against Pt/C and provides vital information on materials discovery for the ORR.

A current limitation to improving the volumetric energy density of Na-ion batteries is the low density of the hard carbon(HC) anode. This problem can be solved by using high-density, high-capacity materials like SnS, which reacts with Na over a combined conversion and alloying reaction that theoretically provides 1022 mAh g-1 and 5335 mAh cc-1(materials level). Here, composites containing SnS and thermally activated graphite(t-G) are prepared by ball-milling and tested with different electrolyte solutions. Adding 5 wt.% of t-G is sufficient to obtain significant improvements in capacity and cycle life, reaching 608 mAh g-1 initially and 439 mAh g-1 after 100 cycles. Even without calendaring, the obtained volumetric capacity of 283 mAh cc-1 (electrode level) is already on-par with commercial HC electrodes. Moreover, ether-based electrolytes are found to be superior to ester-based electrolytes, enabling high storage capacity and cycle life. The reaction is investigated by  operando  X-ray diffraction and operando dilatometry. The inferior performance in ester-based electrolytes is found to be due to a larger polarization that largely prevents the alloying reaction that occurs close to 0 V. Over cycling, the conversion reaction becomes gradually inactive while the alloying reaction shows a much better degree of reversibility.

Self-assembled monolayers (SAMs) have revolutionized the fabrication of lead-based perovskite solar cells, but they still remain underexplored in tin perovskite systems. To date, PEDOT remains the most effective hole-selective layer in tin perovskite solar cells (TPSCs), yet it presents challenges for both performance and stability. MeO-2PACz, the only SAM reported for tin perovskites consistently underperforms when compared to PEDOT. In this work, it is identified that MeO-2PACz's limitations stem from excessively strong interactions with the perovskite surface and poor lattice matching, which leads to inferior interface quality. To address these issues, a novel SAM-forming molecule called Th-2EPT is designed, synthesized, and characterized. Density functional theory (DFT) is used to evaluate coordination strength and lattice compatibility, complemented by electro-optical characterisation techniques that show significantly reduced interfacial recombination and improve material crystallinity in Th-2EPT/Perovskite films. With Th-2EPT, the first SAM-based tin perovskite solar cells that outperform PEDOT-based devices, delivering a power conversion efficiency (PCE) of 8.2% with a DMSO-free solvent system, are demonstrated.

Advancing inverted perovskite solar cells requires effective strategies to mitigate nonradiative recombination at the perovskite/C-60 interface. Here, we report a volatile material that forms a thin, dense interlayer that essentially eliminates the C-60-induced nonradiative interfacial recombination loss despite not directly passivating the perovskite surface. Ultraviolet photoelectron spectroscopy highlights that the molecule forms a positive dipole layer on the surface that aligns the perovskite and C-60 energy levels for electron conduction. Furthermore, the molecule's volatile nature allows the use of a high-concentration solution that enables a high surface coverage (likely >99%) without increasing the thickness. The combination of these two effects yields an effective approach to suppressing interface recombination. The resulting triple cation perovskite solar cells achieved a power conversion efficiency of >25% and the devices maintain >90% of their initial efficiency after 1200 h of operation. Furthermore, the molecule is broadly applicable to various perovskite compositions and bandgaps.

Transition Metal Dichalcogenides (TMDCs) are promising semiconductor alternatives to silicon in CMOS technology. Their layered nature allows scaling to a single layer (1L) without degrading electrical performance, enabling further miniaturization of field‐effect transistors (FETs). TMDCs like WSe 2 exhibit ambipolar transport, allowing fabrication of both p ‐type and n ‐type devices on a single flake, simplifying circuit design. Ambipolar, large‐area, high‐quality 1L‐WSe 2 is therefore highly desirable. Here, centimeter‐scale exfoliated 1L‐WSe 2 is achieved, reaching 1L areas of up to 20 mm 2 via thermally activated gold‐mediated TMDC exfoliation using large, high‐quality WSe₂ parent crystals. The quality of 1L‐WSe2 is comprehensively investigated via Raman spectroscopy, photoluminescence, X‐ray, and ultraviolet photoelectron spectroscopy, as well as electronic transport measurements. For the latter, 1L‐WSe 2 ‐based FETs are fabricated on lithium‐ion conducting glass ceramic substrates serving as both supporting substrate and high‐performance gate. Subthreshold slopes as steep as 30 and 50 mV dec −1 , maximum mobilities of 15 and 18 cm 2 V⁻¹ s⁻¹, and ON/OFF ratios of ≈10 8 and 10 9 for electron and hole currents, respectively, are achieved at ultra‐low gate voltages (≈2 V). The performance, demonstrated across 15 devices, suggests that 1L‐WSe 2 in this device architecture can pave the way toward providing an alternative to conventional silicon‐based CMOS technology for innovative, further miniaturized devices.

The built-in voltage (VBI) is a key parameter for solar cell operation, yet in perovskite solar cells the distribution, magnitude, and origin of the VBI remains poorly understood. In this work, we systematically studied the VBI in pin-type perovskite solar cells based on different hole transport layers (TLs). To this end, we determine the surface photovoltage (SPV) of partial and complete device stacks layer-by-layer by measuring the work function (WF) under dark and light (equivalent AM1.5G) conditions with Kelvin probe (KP) and photoemission spectroscopy (UPS) measurements in 3 different laboratories. We demonstrate that the SPV increases upon the addition of each additional layer until it equals the open-circuit voltage (VOC) of the full device. This suggests that both the electron and hole transport layer (HTL/ETL) enlarge the SPV, by improving the separation of photogenerated carriers. Yet, the contribution of both transport layers to the total SPV of the device is small (in the range of ≈100 to 200 meV) and the largest contribution to the SPV originates from the top metal electrode (≈500 meV). The results suggest that the VBI of pin-type perovskite solar cells is largely a result of the work-function difference of the electrodes. With regard to films (or incomplete cell stacks), our simulations can reproduce the measured SPV, and measured quasi-Fermi level splitting (>VOC) in partial cell stacks without a significant internal field consistent with the experimental data. This work establishes layer-by-layer SPV measurements, which are easily accessible, as a key tool for understanding device performance and internal energetics, similar to layer-by-layer QFLS measurements.

The stability and performance of metal halide perovskite (MHP) optoelectronic devices are significantly influenced by the chemical and electronic properties of their interfaces, often studied using photoelectron spectroscopy (PES). MHP films, containing organic cations, are susceptible to surface modifications under common experimental conditions, necessitating careful analysis. This study examines the effects of argon gas cluster ion beam (GCIB) sputtering, considered gentler and more suitable for depth‐profiling than standard argon ion sputtering, on methylammonium lead iodide using PES. Long‐term exposure to argon clusters with 3.2 and 1.5 eV per Ar atom causes significant degradation, including cation loss and metallic lead formation. However, short‐term exposure (<60 min) at 1.5 eV per Ar atom effectively reduces surface contamination without noticeable degradation, allowing access to intrinsic electronic properties. This gentle cleaning reveals a 220 meV energy difference between the contaminated surface and the valence band onset of the intrinsic MHP potentially improving energy level alignment with electron transport layers. These results demonstrate that low energy GCIB sputtering can serve as a non‐destructive surface cleaning method, enhancing PES investigations and supporting fundamental device studies of MHPs.

Different Pt structures were deposited on WO3 by using atomic layer deposition. The gas sensing properties, structures of the Pt loadings, and their influence on the gas detection mechanism were investigated using extensive material characterization and operando spectroscopies. The results show that, depending on the number of atomic layer deposition cycles, different Pt structures can be obtained, which influence the gas detection in different ways. The found structures range from predominantly ionic Pt sites over oxidic particles to partially oxidized metallic particles. It was found that single ion sites and small oxidic particles have the most effective influence on gas detection, whereas partially oxidized metal particles lead to a lower gas sensing performance.

Electric gating in atomically thin field-effect devices based on transition-metal dichalcogenides has recently been employed to manipulate their excitonic states, even producing exotic phases of matter, such as an excitonic insulator or Bose-Einstein condensate. Here, we mimic the electric gating effect of a bilayer-MoS2 on graphite by charge transfer induced by the adsorption of molecular p- and n-type dopants. The electric fields produced are evaluated from the electronic energy-level realignment and Stark splitting determined by X-ray and UV photoelectron spectroscopy measurements and compare very well with literature values obtained by optical spectroscopy for similar systems. We then show that analysis of the inhomogeneous broadening and energy shifts of the quantum-well states of the valence band allows extraction of the full electric potential profile and charge-density redistribution across the entire heterojunction with atomic-scale precision, which is not accessible by other methods.

A critical step in realizing the vision of green hydrogen through water splitting is to design oxygen evolution reaction (OER) catalysts that showcase a good balance of activity and stability. This work reports the compositional tuning of a NiMoO4 material and then the subsequent varying of Ti3C2T x MXene with the NiMoO4 hybrid nanostructures as OER catalysts in alkaline media. In this work, the optimum NiMoO4 hybrid catalyst retained good stability over 24 h of chronopotentiometry on industrial relevant supports (Ni Felt) with an overpotential value of ca. 339 mV at 100 mA cm-2. Operando Raman spectroscopy revealed that catalytically active β-NiOOH species are formed during OER in NiMoO4 at lower overpotentials than for pure NiO and that a higher amount of the β-NiOOH was found in the 5% MXene loading. The ICP-OES analysis showed that Mo dissolution follows a volcano trend with MXene loading (peaking at 5 wt %) before decreasing at 10 wt %. Overall, these results hold great promises for rational design strategies for MXene-supported water oxidation catalysts in alkaline electrolytes.

Tin perovskite solar cells are emerging as a sustainable lead-free alternative in thin film photovoltaics. DMSO-free processed tin perovskites are gaining interest due to the detrimental effects of DMSO on tin oxidation. However, replacing DMSO with other solvents remains challenging due to the accelerated crystallization dynamics in non-DMSO systems. In this study, the crystallization process in a DMSO-free solvent system is regulated by managing the transition from the sol-gel phase to the solid film. Specifically, piperazine dihydriodide (PDAI) and 4-tert-butylpyridine (tBP) are utilized to coordinately tune the colloidal chemistry through forming large pre-nucleation clusters in perovskite ink, further, facilitating the film formation process. By combining tBP and PDAI, a controllable crystallization rate is achieved as evidenced by in situ photoluminescence (PL) measurement during spin-coating. As a result, tin perovskite films show high crystallinity and improved microstructure. Devices treated with tBP+PDAI exhibit a champion power conversion efficiency of 7.8% and excellent stability without observable degradation for over 3000 h stored in the N2 glovebox. These findings advance understanding and managing crystallization in DMSO-free solvents processed tin perovskite solar cells.

The current state‐of‐the‐art catalysts for the oxygen evolution reaction (OER) in an anion exchange membrane (AEM) electrolyser are not efficient enough to surpass green H 2 produced by other electrolyser technologies, such as Proton Exchange Membrane (PEM) electrolysers. One reason for this is due to the AEM catalysts not being active enough and lacking long‐term stability. In this work, we combine Ni based material with Ti 3 C 2 T x MXene at different loadings (1, 5 and 10 %) to understand the effect of the MXene on the OER activity and stability. Our results show that the amount of MXene not only affects the OER performance, but the materials surface is also altered. Interestingly, the Ti 3 C 2 T x is still present in the bulk for all composites but the surface of the composites contains different amounts of oxidized Ti 3 C 2 T x i.e. TiO 2 . The optimum material in this study for the OER is the NiO x /1 %Ti 3 C 2 T x which can be rationalized by the lower Ti/Ni ratio in the starting materials hence producing less overall surface TiO 2 during OER. Additionally, when the pure NiO x and the 1 % Ni‐Ti 3 C 2 T x are compared by operando Raman spectroscopy, the NiO x /1 %Ti 3 C 2 T x exhibits β‐NiOOH at lower overpotentials, which is known to be present for efficient OER on Ni materials.