Search

Electrochemical CO2 reduction (CO2R) is an attractive option for storing renewable electricity and for the sustainable production of valuable chemicals and fuels. In this roadmap, we review recent progress in fundamental understanding, catalyst development, and in engineering and scale-up. We discuss the outstanding challenges towards commercialization of electrochemical CO2R technology: energy efficiencies, selectivities, low current densities, and stability. We highlight the opportunities in establishing rigorous standards for benchmarking performance, advances in in operando characterization, the discovery of new materials towards high value products, the investigation of phenomena across multiple-length scales and the application of data science towards doing so. We hope that this collective perspective sparks new research activities that ultimately bring us a step closer towards establishing a low- or zero-emission carbon cycle.

The increasing concern for the environment and the negative impacts associated with carbonaceous compounds have driven the demand for greener and more sustainable chemical manufacturing technologies. Photoelectrochemical (PEC) technology provides an environmental and sustainable pathway for producing high value-added products by upgrading glycerol, a surplus by-product of biodiesel from biomass, while coupling with the production of high-purity hydrogen. As an emerging area, the major limiting factor in PEC glycerol oxidation is the lack of high selectivity and conversion, attributed to the parallel and sequential oxidation steps resulting from different bond cleavage positions and varying degrees of oxidation. This review aims to present a comprehensive summary of the current state of PEC glycerol oxidation from various perspectives, including product distribution, photoanode design, and oxidation mechanisms. A particular emphasis is placed on the different photoanodes used in glycerol oxidation and possible strategies for improving the activity and selectivity, including morphology and crystallization control, doping, defect engineering, metal loading, heterojunction formation, and co-catalyst deposition. Finally, we provide a comprehensive discussion of the technical challenges and future prospects for efficient PEC glycerol oxidation coupled with hydrogen production. [ABSTRACT FROM AUTHOR]

Efficient wide-bandgap perovskite solar cells (PSCs) enable high-efficiency tandem photovoltaics when combined with crystalline silicon and other low-bandgap absorbers. However, wide-bandgap PSCs today exhibit performance far inferior to that of sub-1.6-eV bandgap PSCs due to their tendency to form a high density of deep traps. Here, we show that healing the deep traps in wide-bandgap perovskites-in effect, increasing the defect tolerance via cation engineering-enables further performance improvements in PSCs. We achieve a stabilized power conversion efficiency of 20.7% for 1.65-eV bandgap PSCs by incorporating dipolar cations, with a high open-circuit voltage of 1.22 V and a fill factor exceeding 80%. We also obtain a stabilized efficiency of 19.1% for 1.74-eV bandgap PSCs with a high open-circuit voltage of 1.25 V. From density functional theory calculations, we find that the presence and reorientation of the dipolar cation in mixed cation-halide perovskites heals the defects that introduce deep trap states.

Quasi-two-dimensional (quasi-2D) perovskites exhibit excellent performance in light-emitting diodes (LEDs). However, the quality of perovskite films prepared via the solution method is significantly impacted by the enormous number of defects that unavoidably form at the grain boundaries and interfaces during the precursor to the crystal formation process. Here, we propose a strategy to assist perovskite crystallization and defect passivation at the buried interface through interfacial modification. The organic ammonium salt, ethylamine chloride (EACl), is added to the hole transport material and modifies the buried interface of the perovskite film. EACl introduces the nucleation sites for perovskite precursors, and promotes the crystallization process of the perovskite grains, contributing to the formation of high-quality perovskite films. At the same time, the presence of Lewis base (–NH2) groups in EACl and their lone electron pairs effectively inactivate unlocated Pb2+ ions at the buried interface, thereby reducing non-radiative recombination. In addition, chloride ions help to mitigate defects and to improve the morphology of perovskite films. Devices with this modification show a higher performance than control devices on all metrics. This work proposes a facile but efficient way for improving quasi-2D pure blue perovskite crystallization and growth. [ABSTRACT FROM AUTHOR]

The development of a methodology for synthesizing value‐added urea (CO(NH2)2) via a renewable electricity‐driven C−N coupling reaction under mild conditions is highly anticipated. However, the complex catalytic active sites that act on the carbon and nitrogen species make the reaction mechanism unclear, resulting in a low efficiency of C−N coupling from the co‐reduction of carbon dioxide (CO2) and nitrate (NO3−). Herein, we propose a novel tandem catalyst of Mo‐PCN‐222(Co), in which the Mo sites serve to facilitate nitrate reduction to the *NH2 intermediate, while the Co sites enhance CO2 reduction to carbonic oxide (CO), thus synergistically promoting C−N coupling. The synthesized Mo‐PCN‐222(Co) catalyst exhibited a noteworthy urea yield rate of 844.11 mg h−1 g−1, alongside a corresponding Faradaic efficiency of 33.90 % at −0.4 V vs. reversible hydrogen electrode (RHE). By combining in situ spectroscopic techniques with density functional theory calculations, we demonstrate that efficient C−N coupling is attributed to a tandem system in which the *NH2 and *CO intermediates produced by the Mo and Co active sites of Mo‐PCN‐222(Co) stabilize the formation of the *CONH2 intermediate. This study provides an effective avenue for the design and synthesis of tandem catalysts for electrocatalytic urea synthesis. [ABSTRACT FROM AUTHOR]

Electrochemical biomass conversion holds promise to upcycle carbon sources and produce valuable products while reducing greenhouse gas emissions. To this end, deep insight into the interfacial mechanism is essential for the rational design of an efficient electrocatalytic route, which is still an area of active research and development. Herein, we report the reduction of dihydroxyacetone (DHA)—the simplest monosaccharide derived from glycerol feedstock—to acetol, the vital chemical intermediate in industries, with faradaic efficiency of 85±5 % on a polycrystalline Cu electrode. DHA reduction follows preceding dehydration by coordination with the carbonyl and hydroxyl groups and the subsequent hydrogenation. The electrokinetic profile indicates that the rate‐determining step (RDS) includes a proton‐coupled electron transfer (PCET) to the dehydrated intermediate, revealed by coverage‐dependent Tafel slope and isotopic labeling experiments. An approximate zero‐order dependence of H+ suggests that water acts as the proton donor for the interfacial PCET process. Leveraging these insights, we formulate microkinetic models to illustrate its origin that Eley–Rideal (E−R) dominates over Langmuir–Hinshelwood (L−H) in governing Cu‐mediated DHA reduction, offering rational guidance that increasing the concentration of the adsorbed reactant alone would be sufficient to promote the activity in designing practical catalysts. [ABSTRACT FROM AUTHOR]

Realizing the horizontal orientation of molecular transition dipole moment (TDM) can greatly improve the out‐coupling efficiency and the resultant external quantum efficiency (EQE) of organic light‐emitting diodes (OLEDs). Herein, key parameters governing the horizontal TDM have been continuously explored. However, quantitatively identifying the key parameters from the molecular structure viewpoint is rather challenging due to the complexity of the influencing parameters. Here, by training the machine learning (ML) models using the experimental results, the quantitative relationship between the molecular structure and the horizontal TDM ratio (ϴ) of thermally activated delayed fluorescent (TADF) emitters in the host‐guest films is identified. The molecular structure is represented by either quantum chemistry‐calculated structural descriptors or topological/physical/chemical molecular descriptors. Key descriptors are ranked and can be used for guiding molecular structure design. Moreover, the accuracy of ML models is double‐verified by comparing the predicted results with experimental ϴ values and the trend of experimental EQE based on a group of materials. Using compressed sensing technology, the low‐dimension material space is also visually constructed based on key descriptors, and the results are consistent with those of the ML models. [ABSTRACT FROM AUTHOR]

In p–i–n type lead halide perovskite solar cells (PSCs), the poor wettability of the perovskite solution on the typically used hole transport layer, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), is detrimental to obtaining high quality perovskite films. Moreover, the formation of excess lead iodide (PbI2) deteriorates the device stability. Herein, by introducing diamine hydrobromides with different lengths on the PTAA layer, its wettability is greatly increased, leading to a more uniform perovskite film and reduced trap density. Moreover, diamine hydrobromide can reduce excess PbI2. Density functional theory (DFT) calculations further prove the strong interaction between diamine hydrobromides and PbI2; diamine hydrobromides with different lengths present different binding energies with PbI2. Among them, hexanediamine hydrobromate (HDADBr) has the lowest binding energy with PbI2 and enables the least traps formed in the device. Moreover, HDADBr also has the weakest interaction with the I−-rich perovskite surface, and the distribution of the I density of states is expanded, which is more conducive to the diffusion of charge carriers. The best-performing PSC is achieved when HDADBr is used, which exhibits an improved power conversion efficiency (PCE) of 20.22% from 18.41% of the control device. The device stability is also notably improved; the PCE of the unencapsulated PSC remains at 90% of the initial value after 400 h of degradation. [ABSTRACT FROM AUTHOR]

Background: In this study, an apple foam net packing machine is designed to improve the efficiency of apple foam net packing, reduce the intensity of manual work, and meet the market demand for diverse forms of apple packing. Methods: Based on the analysis of apple shape characteristics, a secondary posture adjustment method for apples with a vertical posture adjustment mechanism and a side posture adjustment mechanism is proposed. Based on the observation of human hand-set nets and the analysis of the mechanical characteristics of nets, a dual-system net opening method combining a net slackening system and a net opening system is proposed. Results: The experiment shows that: the apple foam net sleeve packing machine can reach 99% of the apple's posture adjustment rate, the net opening rate can reach 99%, and the packing rate can reach 98.10%. The packing speed is 10 s/pcs, and the packing efficiency is 355–365 pcs/h. The length of the fused mesh net sleeve is mainly distributed between 138 and 143 mm, which accounts for approximately 80% of the total number of samples. Conclusions: The apples packed by this machine are neatly packaged according to specifications. It can improve the efficiency of apple foam net sleeve packing and replace manual work. [ABSTRACT FROM AUTHOR]

The direct electrochemical nitric oxide reduction reaction (NORR) is an attractive technique for converting NO into NH3 with low power consumption under ambient conditions. Optimizing the electronic structure of the active sites can greatly improve the performance of electrocatalysts. Herein, we prepare body‐centered cubic RuGa intermetallic compounds (i.e. bcc RuGa IMCs) via a substrate‐anchored thermal annealing method. The electrocatalyst exhibits a remarkable NH4+ yield rate of 320.6 μmol h−1 mg−1Ru with the corresponding Faradaic efficiency of 72.3 % at very low potential of −0.2 V vs. reversible hydrogen electrode (RHE) in neutral media. Theoretical calculations reveal that the electron‐rich Ru atoms in bcc RuGa IMCs facilitate the adsorption and activation of *HNO intermediate. Hence, the energy barrier of the potential‐determining step in NORR could be greatly reduced. [ABSTRACT FROM AUTHOR]

A proper theoretical quantization-distortion model for hybrid video coding is always desirable, since this allows us to explain the behavior of existing codecs and to design better ones. However, due to the existence of motion-compensated prediction, hybrid video coding introduces interframe dependency into the encoded video, which makes its quantization-distortion characteristics difficult to analyze. In this paper, a joint analysis of quantization and motion-compensated prediction is presented. For a complete analysis, we investigate not only the distortion that quantization introduces into video signal, but also its effect on motion-compensated prediction. Based on the joint analysis, a quantization-distortion model of hybrid video coding is proposed. Our extensive experimental results show that the proposed model can estimate the quantization-distortion curve of hybrid video coding with high accuracy. Furthermore, the estimation accuracy remains high for various video sequences and encoder configurations. Index Terms--Coding distortion, hybrid video coding, motion-compensated prediction, quantization, video modeling.

Denoising module is required by any practical video processing systems. Most existing denoising schemes are spatiotemporal filters which operate on data over three dimensions. However, to limit the number of inputs, these filters only utilize one reference frame and cannot fully exploit temporal correlation. In this paper, a recursive temporal denoising filter named multihypothesis motion compensated filter (MHMCF) is proposed. To fully exploit temporal correlation, MHMCF performs motion estimation in a number of reference frames to construct multiple hypotheses (temporal predictions) of the current pixel. These hypotheses are combined by weighted averaging to suppress noise and estimate the actual current pixel value. Based on the multihypothesis motion compensated residue model presented in this paper, we investigate the efficiency of MHMCF, and some numerical evaluations are revealed. Experimental results show that MHMCF demonstrates quite good denoising performance while the inputs are much fewer than spatio-temporal filters. Moreover, as a purely temporal filter, it can well preserve spatial details and achieve satisfactory visual quality. Index Terms--Least squares estimator, multihypothesis motion compensation, video denoising, video modeling.