Boosting Nitrate to Ammonia Electroconversion through Hydrogen Gas Evolution over Cu-foam@mesh Catalysts.

The hydrogen evolution reaction (HER) is often considered parasitic to numerous cathodic electro-transformations of high technological interest, including but not limited to metal plating (e.g., for semiconductor processing), the CO2 reduction reaction (CO2RR), the dinitrogen → ammonia conversion (N2RR), and the nitrate reduction reaction (NO3-RR). Herein, we introduce a porous Cu foam material electrodeposited onto a mesh support through the dynamic hydrogen bubble template method as an efficient catalyst for electrochemical nitrate → ammonia conversion. To take advantage of the intrinsically high surface area of this spongy foam material, effective mass transport of the nitrate reactants from the bulk electrolyte solution into its three-dimensional porous structure is critical. At high reaction rates, NO3-RR becomes, however, readily mass transport limited because of the slow nitrate diffusion into the three-dimensional porous catalyst. Herein, we demonstrate that the gas-evolving HER can mitigate the depletion of reactants inside the 3D foam catalyst through opening an additional convective nitrate mass transport pathway provided the NO3-RR becomes already mass transport limited prior to the HER onset. This pathway is achieved through the formation and release of hydrogen bubbles facilitating electrolyte replenishment inside the foam during water/nitrate co-electrolysis. This HER-mediated transport effect "boosts" the effective limiting current of nitrate reduction, as evidenced by potentiostatic electrolyses combined with an operando video inspection of the Cu-foam@mesh catalysts under operating NO3-RR conditions. Depending on the solution pH and the nitrate concentration, NO3-RR partial current densities beyond 1 A cm-2 were achieved

The capping agent is the key: Structural alterations of Ag NPs during CO2 electrolysis probed in a zero-gap gas-flow configuration

We apply silver nanoparticles (Ag NPs) as catalysts of CO2reduction in a zero-gap gas-flow electrolyser.Ag NPs stabilized by different ligands —branched polyethylenimine (BPEI), polyvinylpyrrolidone (PVP),polyethylene glycol (PEG), and citrate— are used in the experiments. The as-prepared NPs have almostidentical initial size distributions, yet their catalytic performance, in terms of achievable current andCO selectivity, is different. During electrolysis all Ag NPs exhibit unambiguous morphology changes;the degradation pathway they follow, however, markedly depends on the chemical nature of the cappingagent stabilizing them. Scanning electron micrographs obtained before and after constant-charge elec-trolyses carried out at different potentials reveal that amongst the studied ligands, BPEI seems to bethe most effective stabilizer of Ag NPs; in turn, however, BPEI also limits CO formation the most. In caseof PVP, mostly corrosion (particle shrinkage) is observed at practically relevant electrolysing potentials,while the application of PEG leads more to particle coalescence. Ostwald ripening seems to appear only athigh applied (H2forming) potentials in case of the three afore-mentioned ligands while in case of citrateit becomes significant already at mild (CO forming) voltages. By studying the effects of capping agentremoval and exchange we demonstrate that apart from ligands directly attached to the Ag NPs, alsothe excess of capping agents (adsorbed on the electrode surface) plays a decisive role in determiningthe extent and mode of catalyst degradation. The results of SEM-based particle sizing are also confirmedby synchrotron based wide-angle X-ray scattering measurements that provide further insight into theevolution of crystallite size and lattice strain in the applied Ag NPs during electrolysis

Development of China’s first space-borne aerosol-cloud high-spectral-resolution lidar: retrieval algorithm and airborne demonstration

Aerosols and clouds greatly affect the Earth’s radiation budget and global climate. Light detection and ranging (lidar) has been recognized as a promising active remote sensing technique for the vertical observations of aerosols and clouds. China launched its first space-borne aerosol-cloud high-spectral-resolution lidar (ACHSRL) on April 16, 2022, which is capable for high accuracy profiling of aerosols and clouds around the globe. This study presents a retrieval algorithm for aerosol and cloud optical properties from ACHSRL which were compared with the end-to-end Monte-Carlo simulations and validated with the data from an airborne flight with the ACHSRL prototype (A2P) instrument. Using imaging denoising, threshold discrimination, and iterative reconstruction methods, this algorithm was developed for calibration, feature detection, and extinction coefficient (EC) retrievals. The simulation results show that 95.4% of the backscatter coefficient (BSC) have an error less than 12% while 95.4% of EC have an error less than 24%. Cirrus and marine and urban aerosols were identified based on the airborne measurements over different surface types. Then, comparisons were made with U.S. Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) profiles, Moderate-resolution Imaging Spectroradiometer (MODIS), and the ground-based sun photometers. High correlations (R > 0.79) were found between BSC (EC) profiles of A2P and CALIOP over forest and town cover, while the correlation coefficients are 0.57 for BSC and 0.58 for EC over ocean cover; the aerosol optical depth retrievals have correlation coefficient of 0.71 with MODIS data and show spatial variations consistent with those from the sun photometers. The algorithm developed for ACHSRL in this study can be directly employed for future space-borne high-spectral-resolution lidar (HSRL) and its data products will also supplement CALIOP data coverage for global observations of aerosol and cloud properties

Evaluating the Effects of Renewable Energy Consumption on Carbon Emissions of China’s Provinces: Based on Spatial Durbin Model

Renewable energy consumption is considered as the main form of energy consumption in the future. The carbon emissions produced by renewable energy can be approximately ignored, and renewable energy is essential for regional sustainable development. In this study, we used the Durbin model with panel data to explore the spatial dependence between renewable energy consumption the and carbon emissions of China’s 30 provinces from 1997 to 2017. The results show that: (1) there is a negative spatial correlation between renewable energy consumption and carbon emissions, and “High-Low” areas are mainly concentrated in southern provinces in 1997–2011; (2) the center of gravity of renewable energy consumption moves southwest, which is consistent with the center of gravity of carbon emissions; (3) renewable energy consumption has a significant inhibitory effect on carbon emissions of a local region, but the spatial spillover effect is not significant. Specifically, a 1% increase in renewable energy consumption in a region will reduce carbon emissions by 0.05%. Finally, on the basis of this study, it was proposed to give full play to the advantages of renewable energy in the western region, and further accelerate the development of the renewable energy industry

Limitations of Identical Location SEM as a Method of Degradation Studies on Surfactant Capped Nanoparticle Electrocatalysts

Identical location scanning electron microscopy (IL–SEM) has become an important tool for electrocatalysis research in the past few years. The method allows for the observation of the same site of an electrode, often down to the same nanoparticle, before and after electrochemical treatment. It is presumed that by IL–SEM, alterations in the surface morphology (the growth, shrinkage, or the disappearance of nanosized features) can be detected, and the thus visualized degradation can be linked to changes of the catalytic performance, observed during prolonged electrolyses. In the rare cases where no degradation is seen, IL–SEM may provide comfort that the studied catalyst is ready for up-scaling and can be moved towards industrial applications. However, although it is usually considered a non-invasive technique, the interpretation of IL–SEM measurements may get more complicated. When, for example, IL–SEM is used to study the degradation of surfactant-capped Ag nanocubes employed as electrocatalysts of CO2 electroreduction, nanoparticles subjected to the electron beam during pre-electrolysis imaging may lose some of their catalytic activity due to the under-beam formation of a passive organic contamination layer. Although the entirety of the catalyst obviously degrades, the spot mapped by IL–SEM reflects no or little changes during electrolysis. The aim of this paper is to shed light on an important limitation of IL–SEM: extreme care is necessary when applying this method for catalyst degradation studies, especially in case of nanoparticles with surface-adsorbed capping agents