Catalytic conversion of NO_x into ammonia is a significant step towards sustainable energy, requiring efficient materials for environmental NO_x detection and its subsequent reduction to amines. While chemiresistive sensing has been realized as technically distinct from the conventional oxygen reduction reaction (ORR), the development of smart catalytic materials which can detect trace-level NO_x and also demonstrate efficient ORR capabilities is crucial. In this proof-of-concept work, Sb single atoms (SAs) have been monodispersed on a nitrobenzene-intercalated few-layered MnPS₃ crystal-surface, for efficient room-temperature NO₂ detection. The sensing properties have been found to be influenced by polarized-monochromatic light and SA loading, with the response being maximum at an ∼50° polarization angle for green light and 3.5% SA content. Under controlled experimental conditions of humidity and pressure, the abovementioned novel composition exhibited ORR response, with ammonia generated at a weight hourly space velocity of 40 000 ml g_cat⁻¹ h⁻¹ and a rate of 4700 μmol g⁻¹ h⁻¹. X-ray absorption spectroscopy revealed the atomic environment of Sb SAs. Quasi-operando micro-photoluminescence combined with Raman spectroscopy identified the role of the MnPS₃ network in facilitating surface NO₂ adsorption. Theoretical calculations delineated the selective and energetic role of Sb SAs in sensing and initiating the ORR, elucidating the reaction pathway in terms of a reduction in Gibbs energy.

Aquatic bacterial rhodopsin proton pumps harvest light energy for photoheterotrophic growth and are known to contain hydroxylated carotenoids that expand the wavelengths of light utilized, but these have not been characterized in marine archaea. Here, by combining a marine chromophore extract with purified archaeal rhodopsins identified in marine metagenomes, we show light energy transfer from diverse hydroxylated carotenoids to heimdallarchaeial rhodopsins (HeimdallRs) from uncultured marine planktonic members of ‘Candidatus Kariarchaeaceae’ (‘Candidatus Asgardarchaeota’). These light-harvesting antennas absorb in the blue-light range and transfer energy to the green-light-absorbing retinal chromophore within HeimdallRs, enabling the use of light that is otherwise unavailable to the rhodopsin. Furthermore, we show elevated proton pumping by the antennas in HeimdallRs under white-light illumination, which better simulates the light conditions encountered by these archaea in their natural habitats. Our results indicate that light-harvesting antennas in microbial rhodopsins exist in families beyond xanthorhodopsins and proteorhodopsins and are present in both marine bacteria and archaea.

Photosynthetic organisms employ sophisticated mechanisms to mitigate photodamage caused by excessive light energy. Among these, proteins such as the Orange Carotenoid Protein (OCP) and the Helical Carotenoid Protein 4 (HCP4) play a central role in non-photochemical quenching (NPQ), by dissipating excess energy. OCP consists of two domains: the N-terminal domain (NTD), which serves as the effector domain, and the C-terminal domain (CTD), which acts as the regulatory domain. The HCPs, which are homologs of the NTD, perform carotenoid-driven energy quenching, carotenoid transport and reactive oxygen species scavenging in cyanobacteria. CTD homologs (CTDH) are involved in carotenoid uptake and delivery. This study presents the first crystal structure of an apo-HCP4 from Anabaena sp. PCC 7120 at a resolution of 3.1 Å, revealing significant structural differences from the previously determined carotenoid bound form (holo-HCP4). The ligand-binding cavity in apo-HCP4 is occluded by dynamic loops, that must move to afford carotenoid transfer from a transiently bound holo-CTDH. The predicted conformational changes of HCP4 loops and the mobility of CTDH residues create a favorable environment for efficient ligand transfer. Our structural analysis identified HCP4 Tyr48 as a key gating residue, regulating cavity accessibility during carotenoid uptake. Biolayer interferometry experiments demonstrated that apo-HCP4 requires interaction with holo-CTDH for effective carotenoid transfer, emphasizing the interplay between these proteins in the carotenoid transport mechanism. Our findings provide insights into the structural and functional differences between apo- and holo-HCP4, elucidating the regulatory mechanisms underlying carotenoid transport and energy quenching in cyanobacteria. This study advances our understanding of carotenoid-mediated photoprotection and transport.

We aim to better understand the tradeoffs between traditional and reinforcement learning (RL) approaches for energy storage management. More specifically, we wish to better understand the performance loss incurred when using a generative RL policy instead of using a traditional approach to find optimal control policies for specific instances. Our comparison is based on a simplified micro-grid model, that includes a load component, a photovoltaic source, and a storage device. Based on this model, we examine three use cases of increasing complexity: ideal storage with convex cost functions, lossy storage devices, and lossy storage devices with convex transmission losses. With the aim of promoting the principled use RL based methods in this challenging and important domain, we provide a detailed formulation of each use case and a detailed description of the optimization challenges. We then compare the performance of traditional and RL methods, discuss settings in which it is beneficial to use each method, and suggest avenues for future investigation.

The feasibility of a hydrogen-based economy critically depends on the development of catalysts for the hydrogen evolution reaction (HER) that do not rely on Pt or other noble metals. Contemporary efforts are focused on developing first-row transition metal complexes that will be operative at low overpotentials and catalyze the reaction with high efficacy and turnover rates. We now report a surprisingly strong effect of bromide substituents on the structure, coordination chemistry, electronic spectrum, reduction potentials, and catalytic activity of an already electron-poor cobalt corrole. The six-coordinate cobalt(III) complex of the brominated corrole displays a very nonplanar macrocycle, its axial pyridines are perpendicular to each other, the maxima in the electronic spectrum are red-shifted by almost 70 nm, and it is reduced by 600 mV less negative potentials. It catalyzes the HER from an organic acid in an organic solvent with a very low onset potential of −0.96 V vs. the Fc⁺/Fc couple and has been used for the preparation of a catalyst-modified cathode to produce hydrogen gas from acidic water with 97% Faradaic efficacy at potentials as low as −0.4 V vs. RHE.

We now report a surprisingly strong effect of bromide substituents on the structure, coordination chemistry, electronic spectrum, reduction potentials, and catalytic activity of an already electron-poor cobalt corrole.

Purple bacteria convert solar energy into biochemical energy with high quantum efficiency across diverse environments. Under low light, many species increase the number of antenna complexes and replace their primary light-harvesting complex 2 (LH2) with a blue-shifted variant, LH3. The structural basis of the blue shift and its influence on the dynamics of solar energy conversion have remained unclear. Here, we integrated cryogenic electron microscopy, ultrafast spectroscopy, and quantum dynamics simulations to compare LH2 and LH3 from Rhodoblastus acidophilus strain 7750. Our analyses revealed that hydrogen bonding dynamically tunes the transition energy, introducing a previously unreported excitation energy equilibrium between bacteriochlorophyll rings in LH3. This energy redistribution opened new inter-complex pathways, enabling 68% faster energy transport to maintain high conversion efficiency even with the larger antenna. Collectively, these results establish structural modifications as a tunable knob to optimize both absorption and transport for robust light harvesting under fluctuating conditions.

Nickel hydroxide is a leading alternative to platinum group metals for electrocatalysis of the ammonia oxidation reaction (AOR), an important process for energy conversion and environmental remediation. Nevertheless, the dependence of AOR electrocatalysis on the different crystalline phases at the electrode surface (α-Ni(OH)₂/γ-NiOOH vs. β-Ni(OH)₂/β-NiOOH) has never been investigated. Herein, the crystalline β-Ni(OH)₂ and the disordered α-Ni(OH)₂ were synthesized and characterized by XRD, HRSEM, and Raman and FTIR spectroscopies. The respective electrocatalytic activity of the two phases was analysed at a broad range of ammonia concentrations (0.01–2 M) and pH values (11–13). Both phases electrocatalyze the oxidation of NH₃ to N₂, as proven by online mass spectrometry, but the α-Ni(OH)₂/γ-NiOOH couple is more active. At high ammonia concentrations (>1 M), surface poisoning by adsorbed NH₃ prevents access to OH⁻, leading to less NiOOH formation, lower AOR currents, and suppression of the OER side reaction. The poisoning is strong and irreversible on α-Ni(OH)₂, as confirmed by soaking experiments. The difference in ammonia adsorption and electrocatalytic activity between the α-Ni(OH)₂ and β-Ni(OH)₂ emphasizes the importance of understanding the phase space of nickel hydroxide electrodes when designing low-cost electrocatalysts for the nitrogen cycle.

3D printing with earth-based materials is emerging as a sustainable building method; however, challenges remain regarding strength, thermal performance, and both logistical and environmental viability. This study aims to optimize the passive thermal performance and facilitate the industrial applicability of printed envelopes through advanced material and geometric design; implementing a mass-customizable computational toolpath framework, and refining the printing processing parameters. The design approach is guided by experimental exploration and the integration of state-of-the-art knowledge.

The results present a high-strength material mix with over 55 vol% fiber-content, including fibers several centimeters in length, printed using an 8 mm nozzle outlet. The medium-resolution printing method balances efficiency, shape accuracy, and thermal performance. Mechanical tests showed that small, lab-cast specimens achieved compressive strengths of up to 10.6 MPa, surpassing typical cob-like materials. Likewise, thermal conductivity measurements of approximately 0.35–0.37 W/m·K confirm the material's potential for passive temperature regulation. Furthermore, by segmenting the wall into repeatable yet customizable units and integrating cavities and ventilation channels, the system can be adapted to different building sizes, performance requirements, and assembly methods. Full-scale prototypes were printed to evaluate the applicability in buildings. While load-bearing capacity remains limited, results suggest that 3D-printed earth-fiber walls up to 30 cm thick can achieve simulated U-values of approximately 0.8–0.9 W/m²·K. These findings demonstrate that engineered fiber-earth composites, combined with strategic toolpath design, can enhance both mechanical and thermal performance in earthen construction.

Energy-efficient, safe, and reliable Li-ion batteries (LIBs) are required for a wide range of applications. The introduction of ultra-thick graphite anodes, desired for high energy densities, meets limitations in internal electrode transport properties, leading to detrimental consequences. Yet, there is a lack of experimental tools capable of providing a complete view of local processes. Here, a multi-modal operando measurement approach is introduced, enabling quantitative spatio-temporal observations of Li concentrations and intercalation phases in ultra-thick graphite electrodes. Neutron imaging and diffraction concurrently provide correlated multiscale information from the scale of the cell down to the crystallographic scale. In particular, the evolving formation of the solid electrolyte interphase (SEI), observation of gradients in total lithium content, as well as in the formation of ordered Li_xC₆ phases and trapped lithium are mapped throughout the first charge–discharge cycle of the cell. Different lithiation stages co-exist during charging and discharging; delayed lithiation and delithiation processes are observed in central regions of the electrode, while the SEI formation, potential plating, and dead lithium are predominantly found closer to the interface with the separator. The study emphasizes the potential to investigate Li-ion diffusion and the kinetics of lithiation phase formation in thick electrodes.

Agricultural plastics improve crop quality, reduce water use, extend growing cycles, and slow the spread of disease and infestations. Despite such benefits, agricultural plastic waste (APW) is poorly managed. To valorize APW, we propose a two-step process in which APW is pre-hydrothermally treated and then pyrolyzed. Hydrothermal processing (HTP) reduces the elemental oxygen and volatile matter present in raw lignocellulosic biomass. Consequently, we hypothesized that co-HTP of low-density polyethylene (LDPE) and straw would produce a bio-oil with fewer oxygenated compounds upon pyrolysis of the hydrochar than pyrolysis of the raw residues. LDPE, straw and a 4:1 LDPE-to-straw mixture were hydrothermally treated at 250 °C and 300 °C. The hydrochars were then pyrolyzed at 450 °C or 650 °C. Co-HTP produced a pyrolysis bio-oil primarily composed of aliphatic compounds and reduced the number of compounds with oxygen functional groups present. Additionally, co-HTP reduced the devolatilization of straw to a single step at 450 °C, reducing the energy required for the pyrolysis process.