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Abstract: Photocatalytic reforming offers a route to valorize biomass and plastic waste into clean H2 under ambient conditions. However, the scalability of photocatalyst sheets is limited by high-temperature processing, binders and complex co-catalyst deposition. Here a [Co4Zr2O(OnPr)10(acac)4] single-source precursor is deposited onto Al-doped SrTiO3 and immobilized on glass substrates to fabricate photocatalyst sheets using multiple techniques, including high-throughput spray coating. The resulting sheets enable photoreforming of cellulose- and polyethylene terephthalate-derived feedstocks, producing H2 alongside value-added organics such as formate, acetate, glycolate and glycolaldehyde dimer. The system is demonstrated from the centimeter- to meter-squared scale, culminating in a 1-m2 outdoor reactor operating under natural sunlight. After 6 h, H2 yields reached 5.24 and 1.51 mmol m−2 for glucose and pretreated cellulose, respectively, with concurrent formation of oxygenates. Techno-economic analysis based on real-world data estimates an H2 cost of £0.93 mmol−1. This work advances scalable photocatalytic reforming and provides a step towards practical deployment.

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Abstract: A key challenge for incorporation of oxide-based solid electrolytes into batteries remains the brittle nature of the ceramic, which makes scalable, low-cost fabrication of thin (<20 µm) separators challenging. solution-based processing, involving the direct liquid-to-solid transformation of a precursor solution into a ceramic film through deposition and annealing, offers an attractive route to overcome these fabrication challenges while significantly reducing processing temperatures compared to conventional solid-state methods. However, the relationship between the initial choices made in precursor chemistries and the crystallization behavior remains poorly understood, limiting control over the phase formation process. Here, we investigate how the precursor decompositions influence the structure evolution during annealing and crystallization of solution-processed Li-garnet solid electrolyte films. The results reveal a sequence of solvent and precursor decompositions with the Li-precursor, LiNO3, decomposition occurring last and in parallel with the nucleation of La2Zr2O7 as the first crystalline metal-oxide phase. Upon Li-precursor decomposition, the latter is lithiated to form the desired highly conductive cubic Li6.25Al0.25La3Zr2O12 phase. This simultaneity of crystallization and decomposition events demonstrates the importance of the initial precursor choices to control the crystallization process. Through this work, we contribute to fundamental ceramic materials science by establishing a systematic methodology for studying solution-processing and providing a foundation for future precursor design of next-generation solid electrolyte battery components.

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Abstract: NaNiO2 (NNO) has been investigated as a promising sodium-ion battery cathode material, but it is limited by degradation-induced capacity fade. On desodiation, NNO forms multiple phases with large superstructures due in part to Na+-ion vacancy ordering; however, their structures are unknown. Here, we report a structural solution to the Na2/3NiO2 (P′3) desodiated phase using combined Rietveld refinement of high-resolution synchrotron X-ray (SXRD) and neutron powder diffraction (NPD) data, magnetic susceptibility, and 23Na solid-state nuclear magnetic resonance (ssNMR) spectroscopy. Our experimental results are compared to ab initio molecular dynamics (AIMD) simulations, which indicate multiple low-energy structures that are dynamically populated. We observe a combination of competing effects that contribute to the resultant dynamic nature of the structure, including honeycomb ordering of mixed-valence Ni, orbital ordering of Jahn–Teller (JT) distorted Ni3+, and zigzag Na+/vacancy ordering. Our work provides evidence of multiple contributions to the structures of desodiated Na2/3NiO2, along with a framework for investigating the other unsolved desodiated structures. This work may also inform our understanding of the Jahn–Teller evolution in other nickel-rich lithium- and sodium-ion cathodes, such as LiNiO2.

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Abstract: The use of solid-state electrolytes (SSE) promises electrochemical cells with high energy densities as they can enable high-voltage cathodes and lithium metal anodes while minimising the risk of dendrite formation and widening the thermal and electrochemical stability window [1]. Among different types of solid-state electrolytes that have been researched until now, cubic Li7La3Zr2O12 (LLZO) has been shown to have good thermal, mechanical, and electrochemical stability [1]. Nonetheless, one of the main challenges of inorganic SSE is the poor interfacial contact with the electrodes, especially with the cathode active material (CAM). The rigidity of the SSE and CAM makes it necessary to co-sinter the SSE/CAM composite at high temperatures (>1000 ºC) to densify the catholyte to guarantee conformal contact between the solid components [2]. However, CAMs usually react at these temperatures, which leads to formation of poorly lithium-ion conducting intermediate secondary phases due to interdiffusion of atoms and chemical reactions between the SSE and CAM [3]. Recent research elucidating decomposition products resulting from processing of LLZO and various cathode materials has mainly focused on LiCoO2 (LCO) given its high thermodynamical stability against LLZO [4-7]. However, the limited practical reversible capacity of LCO, high cost, and ethical issues concerning cobalt-rich cathode materials motivate the optimisation of other CAMs that are equally stable against LLZO [8]. Among them, LiNixCoyMnzO2 (NMCs) are perceived as strong candidates to decrease the Co content while increasing the specific capacity and maintaining sufficient thermal stability for co-sintering with LLZO [8,9]. A few studies have recently attempted to probe the interfacial stability between LLZO/NMC, but the nature of decomposition products, reaction mechanism, and onset temperature are inconsistent between reports and poorly understood [8-13]. Moreover, these reports do not account for the formation of secondary phases containing dopant elements such as Al3+ in cubic LLZO. To develop a fundamental understanding of the effect of sintering conditions on catholyte composition and reaction products, a comprehensive study of composite materials from microscale to atomic level is required [8]. Commonly used techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), or Raman spectroscopy can provide some information about the material’s local composition but cannot accurately detect any amorphous secondary phases formed in the nanometre scale that are buried at interfaces between SSE and CAM. Consequently, decomposition products can be easily overlooked, resulting in a wide range of reported results. On the other hand, magic angle spinning nuclear magnetic resonance (MAS-NMR) is an ideal technique to identify the decomposition products and probe their local structure even if they are present in small amounts and are highly disordered and amorphous in nature [14]. In this work, we present a detailed characterisation of the changes in the crystal structure and composition of Al-doped LLZO (Al-LLZO) and NMC811 composite as a function of temperature, sintering atmosphere, and conductive agent using ex-situ/variable-temperature XRD, thermogravimetric analysis/differential scanning calorimetry coupled with mass spectrometry (TGA/DSC-MS), and MAS-NMR. Ex-situ 27Al MAS NMR spectroscopy provides evidence of the evolution of Al3+ coordination environment upon annealing, providing accurate and high-resolution atomic scale insights on elemental interdiffusion and reaction onset temperature between Al-LLZO and NMC811.

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Abstract: Heterometal-containing polyoxotitanates (POTs) are much-studied single-source precursors (SSPs) for doped TiO2. In this work the properties of a wide range of lanthanide-containing POTs are studied to assess their potential use as SSPs for Ln–Ti hybrid oxides. The novel cage compounds [{Ti2O(OEt)8}(EtOH·LnCl)]2 (Ln = Sm, Gd, Tb, Dy, Ho, Tm and Yb) are structurally characterised. The magnetic properties of the Ln = Dy and Ho compounds were characterised using SQUID magnetometry—in both cases, there is evidence of significant uniaxial magnetic anisotropy, but magnetic relaxation is fast and therefore no single-molecule magnetic properties are observed. Upon decomposition lanthanide-doped anatase (Ln = La) or titania/LnTi–oxide mixtures are obtained, which show efficient stabilisation of the catalytically active anatase phase up to high temperatures, making the materials of potential interest for applications in photocatalysis.