Abstract Driven by the increasing global demand for sustainable energy, hydrogen-based materials have been extensively explored for a range of energy storage solutions. The 12 sections of this roadmap span multiple fields and applications, providing an assessment of the current worldwide landscape of hydrogen-based materials for energy storage. Each section first summarises the current status of research in each field, before identifying current and future challenges to be addressed. Subsequently, an assessment is made of advances in science and technology to meet those challenges, finishing with concluding remarks. Overall, hydrogen-based materials show exceptional properties for a wide variety of energy storage technologies and have an exciting role to play in the future energy transition, providing many benefits over current alternatives as solid-state and liquid energy stores, thermal energy stores, hydrogen compressors, negative battery electrodes and solid-state electrolytes.
This review presents a comprehensive analysis of silver-alloyed copper indium gallium selenide (ACIGS) thin-film photovoltaic (PV) technology, focusing on its structural, optoelectronic, technological, and economic implications for next-generation solar cells. The global transition toward low-carbon electricity and the increasing demand for high-efficiency, flexible, and resource-efficient PV systems motivate the exploration of advanced absorber materials beyond conventional crystalline silicon. ACIGS emerges as a promising evolution of CIGS, offering improved grain growth, reduced structural and grain-boundary defect densities, enhanced open-circuit voltage, and lower processing temperatures through partial substitution of copper with silver. The review examines vacuum and non-vacuum growth methods, including co-evaporation, sputtering, solution processing, and hybrid approaches, highlighting their influence on film quality, scalability, and industrial relevance. Structural and thermodynamic modifications induced by silver incorporation are discussed in detail, including lattice expansion, phase stability, and metastable behaviour. The impact of Ag alloying on bandgap engineering, defect passivation, carrier recombination, and band alignment is critically analysed, alongside the role of alkali post-deposition treatments in performance optimisation. Special attention is given to ultrathin absorbers, flexible substrates, bifacial and semi-transparent architectures, and tandem integration with perovskites, demonstrating the versatility of ACIGS across emerging PV applications. Finally, techno-economic and sustainability aspects, including material criticality, cost trade-offs, energy payback, and environmental impact, are evaluated. This review identifies both the opportunities and remaining challenges for ACIGS, providing guidance for future research aimed at enabling its broader commercial deployment.
The development of heterogeneous photocatalysts for visible-light CO _2 conversion is a substantial challenge for the sustainable production of chemical resources. On the other hand, homogeneous photocatalytic systems consisting of metal complex photosensitizer and catalyst dissolved in reaction solution have shown excellent photocatalytic performance for CO _2 reduction. Herein, heterogeneous photosensitizer/catalyst complex assemblies were constructed in conjugated networks by simple cross-coupling polymerization of corresponding building molecular building blocks. A conjugated assembly consisting of a [Ru(bpy) _3 ] ^2+ photosensitizer and Ru(bpy)(CO) _2 Cl _2 catalyst served as a visible-light–active photocatalyst for CO _2 reduction into formate. The introduction of a [Ru(bpy) _3 ] ^2+ -type photosensitizing unit enhanced photocatalytic activity owing to its extended visible-light absorption and long-lived excited states. In addition, owing to the intricate rigid conjugated chains connecting the surrounding [Ru(bpy) _3 ] ^2+ core, the conjugated assembly clearly stabilized against ligand dissociation deactivation, which is frequently observed in [Ru(bpy) _3 ] ^2+ -type photosensitizers. Modulating the catalyst unit to Fe(III) tetraphenylporphyrin ( FePor _Cat ) shifted the product selectivity to CO or CH _4 , depending on the reducing power of the photosensitizing unit. This work provides the molecularly characteristic properties of photosensitizing and catalytic complexes into heterogeneous conjugated photocatalysts.
Liquid-phase transmission electron microscopy (LPTEM) bridges the critical gap between bulk electrochemical measurements and nanoscale structural evolution. It offers insight into mechanisms such as metal plating and stripping in batteries, catalyst degradation in fuel cells, and surface reconstruction of electrocatalysts during CO _2 reduction. However, standard LPTEM is frequently hindered by undefined mass transport and severe beam-induced artifacts. This tutorial outlines a rigorous methodology to transition LPTEM from a passive observation tool to a quantitative analytical technique. It details the design of experiments that utilize controlled flow to define the chemical environment, discusses critical material choices, specifically the replacement of standard platinum microelectrodes with carbon-based microelectrodes to minimize catalytic side reactions and improve electron transparency. Furthermore, it provides a workflow for data acquisition and post-processing, demonstrating how to extract volumetric growth kinetics, particle size distributions, and facet evolution metrics from noisy S/TEM videos. Finally, we address common pitfalls, particularly the management of gas evolution during electrochemistry and distinguishing electrochemical nucleation from beam-induced reduction. This guide equips researchers to obtain reproducible, artifact-free, and quantifiable data at the solid-liquid interface during liquid phase electrochemistry.
Abstract Hexagonal boron nitride (hBN) has been reported to improve the ionic conductivity of solid polymer electrolytes for sodium batteries. We previously reported a four–fold increase in ionic conductivity in a poly(ethylene oxide) (PEO) and sodium bis (fluorosulfonylimide) (NaFSI) upon adding hBN at a concentration below the filler critical percolation threshold. However, the mechanism underpinning this enhanced conductivity was not clear. In the present work, we use quasi–elastic neutron scattering (QENS) to investigate polymer segmental dynamics in binary PEO/NaFSI and ternary PEO/NaFSI/hBN electrolytes at a fixed salt concentration of (Na+:EO = 0.05). For the ternary system the hBN concentration is above percolation. We explore the effects of confinement and interfacial behavior on polymer structure and conductivity while observing a doubling in ionic conductivity in the presence of hBN. QENS reveals that hBN leads to a nearly two–fold increase in the fraction of mobile amorphous polymer phase albeit at a lower average relaxation time. To complement the traditional considerations of charge carriers and polymer crystallinity, this study shows the mobile amorphous polymer phase plays a critical role in governing ionic conductivity.
