The limitations of the Haber–Bosch reaction, particularly high-temperature operation, have ignited new interests in low-temperature ammonia-synthesis scenarios. Ambient N2 electroreduction is a compelling alternative but is impeded by a low ammonia production rate (mostly <10 mmol gcat –1 h–1), a small partial current density (<1 mA cm–2), and a high-selectivity hydrogen-evolving side reaction. Herein, we report that room-temperature nitrate electroreduction catalyzed by strained ruthenium nanoclusters generates ammonia at a higher rate (5.56 mol gcat –1 h–1) than the Haber–Bosch process. The primary contributor to such performance is hydrogen radicals, which are generated by suppressing hydrogen–hydrogen dimerization during water splitting enabled by the tensile lattice strains. The radicals expedite nitrate-to-ammonia conversion by hydrogenating intermediates of the rate-limiting steps at lower kinetic barriers. The strained nanostructures can maintain nearly 100% ammonia-evolving selectivity at >120 mA cm–2 current densities for 100 h due to the robust subsurface Ru–O coordination. These findings highlight the potential of nitrate electroreduction in real-world, low-temperature ammonia synthesis.

The last decades have witnessed the discovery of tens of thousands of rare earth (RE) (e.g., Eu2+) and non-RE (e.g., Mn2+) doped photonic materials for near-ultraviolet (NUV) and blue converted white light-emitting diodes (wLEDs), but the future development of wLEDs technology is limited greatly by the intrinsic problems of these traditional dopants, such as the insurmountable visible light reabsorption, the weak absorption strength in NUV or blue region, and so on. Here we report a feasible strategy guided by density functional theory (DFT) calculation to discover novel Bi3+ red luminescent materials, which can solve the above problems eventually. Once the untraditional ion of bismuth is doped into ZnWO4 crystal, multiple defects can be possibly created in different charge states such as BiZn, BiW, interstitial Bi, and even defect complexes of 2 BiZnVW among others, and they, as DFT calculated results illustrate, have the potential to produce emission spanning from visible to near-infrared. As confirmed by experiment, tunable emission can be led to cover from 400 to 800 nm after controls over temperatures, defect site-selective excitation schemes, and the energy transfer between these defects and host. A novel red luminescence was observed peaking at ∼665 nm with a broad excitation in the range of 380–420 nm and no visible absorption, which is evidenced by the temperature-dependent excitation spectra and the diffuse reflection spectra. DFT calculation on defect formation energy shows that BiZn 3+, the valence state of which is identified by X-ray photoelectron spectroscopy, is the most preferentially formed and stable defect inside a single Bi-doped ZnWO4 crystal, and it produces the anomalous red luminescence as confirmed by the single-particle level calculations. Calculation based on dielectric chemical bond theory reveals that the high covalency of the lattice site which Bi3+ prefers to occupy in ZnWO4 is the reason why the emission appears at longer wavelength than the previously reported compounds. On the basis of this work, we believe that future combination of DFT calculation and dielectric chemical bond theory calculation can guide us to efficiently find new phosphors where Bi3+ can survive and emit red light upon NUV excitation. In addition, the DFT calculation on Bi defects in different charge states will help better understand the longstanding as yet unsolved problem on the mechanism of NIR luminescence in bismuth-doped laser materials.

Mechanoluminescent (ML) materials are mechano-optical converters that can emit light under an external mechanical stimulus. All the existing ML materials can only emit light from near ultraviolet to red, which is outside the near-infrared (NIR) windows desired for biomechanical imaging. No studies have been done on doping rare earth (RE) ions with photoluminescence (PL) in the NIR region into a compound to form a ML material that emits NIR light in response to an external force. Here, we show that doping RE ions with a NIR PL into an inorganic compound does not usually result in the formation of a NIR ML material, which can only be achieved in the combination of Nd ions and a CaZnOS compound among the combinations we studied. The newly discovered NIR ML material (CaZnOS:Nd) is biocompatible and can efficiently convert mechanical stress into NIR light over the first and second tissue-penetrating bioimaging window. Its NIR ML emission appeared at a very low force threshold (even when the material was shaken slightly), increased sensitively and linearly with the increase in the force (up to >5 kN), and could penetrate the tissue as deep as >22 mm to enable biomechanical detection. Such a force-responsive behavior is highly reproducible. Hence, CaZnOS:Nd is a new potential ultrasensitive biomechanical probe and expands the ML application horizons into in vivo bioimaging.

Solar-driven photocatalytic oxygen reduction is a potentially sustainable route for the production of hydrogen peroxide (H 2 O 2 ). However, this approach suffers from the limited solubility and slow diffusion of oxygen in water. Another problem is that most photocatalytic oxygen reduction systems do not work well with just water. They often require the addition of sacrificial agents such as alcohols. Here, a covalent organic framework (COF)-based photocatalyst that can reduce O 2 to H 2 O 2 efficiently in pure water under visible-light irradiation is reported. A solar-to-chemical conversion of 0.76% is achieved for H 2 O 2 generation. More importantly, the hydrophobic and mesoporous properties of triphenylbenzene-dimethoxyterephthaldehyde-COF allow the formation of a triphase interface (gas-liquid-solid) when loading this catalyst onto a porous substrate. The H 2 O 2 production rate reaches ≈2.9 mmol g cat −1 h −1 at the triphase interface by overcoming the mass-transfer limitation of O 2 in water. Notably, this rate is 15 times higher than that in a diphase system (liquid-solid). The photoelectrochemical tests reveal that the increase in yield is closely related to the enhanced mass-transfer rate and the higher interfacial O 2 concentration. Furthermore, the triphenylbenzene part is identified as the reactive site based on theoretical calculations.

H 2 O 2 is av ersatile and environmentally friendly chemical involved in water treatment, such as advanced oxidation processes.A nthraquinone oxidation is widely used for large-scale production of H 2 O 2 ,w hichr equires significant energy input and periodic replacement of the carrier molecule. H 2 O 2 production should be customized considering the specific usage scenario.E lectrochemical synthesis of H 2 O 2 can be adopted as alternatives to traditional method, which avoids concentration, transportation, and storage processes. Herein, we identified Bi 2 WO 6 :Mo as al ow-cost and highselectivity choice from as eries of Bi-based oxides for H 2 O 2 generation via two-electron water oxidation reaction. It can continuously provideH 2 O 2 for in situ degradation of persistent pollutants in aqueous solution. Clean energy from H 2 can also be produced at the cathode.T his kind of water splitting producing sustainable resources of H 2 O 2 and H 2 is an advance in environmental treatment and energy science.