Among the electrolyzers under development for CO2 electroreduction at practical reaction rates, gas-fed approaches that use gas diffusion electrodes (GDEs) as cathodes are the most promising. However, the insufficient long-term stability of these technologies precludes their commercial deployment. The structural deterioration of the catalyst material is one possible source of device durability issues. Unfortunately, this issue has been insufficiently studied in systems using actual technical electrodes. Herein, we make use of a morphologically tailored Ag-based model nanocatalyst [Ag nanocubes (NCs)] assembled on a zero-gap GDE electrolyzer to establish correlations between catalyst structures, experimental environments, electrocatalytic performances, and morphological degradation mechanisms in highly alkaline media. The morphological evolution of the Ag–NCs on the GDEs induced by the CO2 electrochemical reduction reaction (CO2RR), as well as the direct mechanical contact between the catalyst layer and anion-exchange membrane, is analyzed by identical location and post-electrolysis scanning electron microscopy investigations. We find that at low and mild potentials positive of −1.8 V versus Ag/AgCl, the Ag–NCs undergo no apparent morphological alteration induced by the CO2RR, and the device performance remains stable. At more stringent cathodic conditions, device failure commences within minutes, and catalyst corrosion leads to slightly truncated cube morphologies and the appearance of smaller Ag nanoparticles. However, comparison with complementary CO2RR experiments performed in H-cell configurations in a neutral environment clearly proves that the system failure typically encountered in the gas-fed approaches does not stem solely from the catalyst morphological degradation. Instead, the observed CO2RR performance deterioration is mainly due to the local high alkalinity that inevitably develops at high current densities in the zero-gap approach and leads to the massive precipitation of carbonates which is not observed in the aqueous environment (H-cell configuration).

Hole transporting materials (HTMs) play a crucial role in achieving highly efficient and stable perovskite solar cells (PSCs). Spirotyped materials being the most widely used HTMs are commonly utilized with dopants, such as Li-TFSI, to improve their carrier mobility significantly. However, dopants could affect the morphology of hole transporting layer negatively by forming defects and pinholes which restrict the performance of devices. Here, we adopt the extended πconjugated structures N-ethylcarbazole and dibenzothiophene to substitute the donor group 4-methoxyphenyl of spiro-OMeTAD, devising two novel HTMs, SC and ST, respectively. Notably, SC possesses low crystallinity and good solubility due to the existence of ethyl in side groups, leading to decent miscibility with Li-TFSI to prevent unfavorable phase-separation. The SC-based device delivers the best power conversion efficiency (PCE) of 21.76% which is higher than that of spiro-OMeTAD (20.73%), attributed to the formation of smooth and pinhole-free morphology. Moreover, it exhibits long-term stability and retains over 90% of initial PCE value for more than 30 days without encapsulation in ambient air. In contrast, the STbased device suffers from dense pinholes induced by its relatively high crystallinity and poor solubility, resulting in a low PCE of 18.18% and inferior stability. Thus, it is effective to modify the side groups in spiro-typed HTMs with specific structures to obtain predictable properties, fabricating PSCs with high efficiency and stability facilely.

The two-dimensional (2D)/three-dimensional (3D) heterojunction perovskite solar cell (PSC) has recently been recognized as a promising photovoltaic structure for achieving high efficiency and long-term stability. Rational design of the 2D spacer cation is important to achieve a win–win situation for defects’ passivation and photogenerated carrier extraction. Herein, we carry out first-principles calculation to analyze the dipole moment of phenethylamine-type molecules and their resulting 2D/3D perovskites. Based on the results of theoretical calculation, the dipole moment of 2D cations can be well tuned by varying the number of fluorine atoms on the para-position of the benzene ring, which further determines the interfacial dipole across the 2D/3D heterojunction interface. A high dipole 2D perovskite layer at the interface between the 3D perovskite and hole-transporting material is found to promote charge transport and suppress charge trapping efficiently. As a result, our 2D/3D PSCs exhibit a champion power conversion efficiency over 22% and a fill factor over 83%. Moreover, our solar cells also show a remarkable stability, maintaining 80% of its initial efficiency for more than 1400 h without encapsulation under a 30 ± 5% relative humidity.

Control over the shape of a metal nanostructure grants control over its properties, but the processes that cause solution-phase anisotropic growth of metal nanostructures are not fully understood. This article shows why the addition of a small amount (75–100 μM) of iodide ions to a Cu nanowire synthesis results in the formation of Cu microplates. Microplates are 100 nm thick and micronwide crystals that are thought to grow through atomic addition to {100} facets on their sides instead of the {111} facets on their top and bottom surfaces. Single-crystal electrochemical measurements show that the addition of iodide ions decreased the rate of Cu addition to Cu(111) by 8.2 times due to the replacement of adsorbed chloride by iodide. At the same time, the addition of iodide ions increased the rate of Cu addition to Cu(100) by 4.0 times due to the replacement of a hexadecylamine (HDA) self-assembled monolayer with the adsorbed iodide. The activation of {100} facets and passivation of {111} facets with increasing iodide ion concentration correlated with an increasing yield of microplates. Ab initio thermodynamics calculations show that, under the experimental conditions, a minority of iodide ions replaces an overwhelming majority of chloride and HDA on both Cu(100) and Cu(111). While Cu nanowire formation is predicted (and observed) in solutions containing chloride and HDA, the calculations indicate that a strong thermodynamic driving force occurs for {111} facet (and microplate) growth when a small amount of iodide is present, consistent with the experiment.

The stacking of 2D perovskites on the top of 3D perovskites has been recognized as a promising interfacial treatment approach to improve the stability and efficiency of planar perovskite solar...

Synthetic control of nanocrystal shape is often achieved by controlling the crystal structure of the seed crystals as well as through the use of additives that are thought to block atomic addition to certain facets. However, the effect of the crystal structure or additives on the rate of atomic addition to a specific facet is not usually quantified, making it difficult to understand and design nanocrystal syntheses. This article combines single-crystal electrochemistry measurements with measurements of anisotropic nanocrystal growth to quantify the roles of citrate and planar defects in anisotropic atomic addition. Citrate lowers the rate of atomic addition to Ag(100) and Ag(111) single crystals by 3.2 and 15 times, respectively. Citrate decreases the rate of ascorbic acid oxidation in a facet-selective manner, but citrate decreases the rate of silver ion reduction to roughly the same extent on Ag(100) and Ag(111) single crystals. The degree to which citrate passivates single-crystal electrodes at different citrate concentrations closely matches the facet-dependent growth rates for single-crystal seeds. In contrast, seeds with planar defects exhibit anisotropic growth that is 30−100 times greater than can be explained by the facet-selective passivation by citrate. Without citrate, more silver deposits on the edges of seeds with planar defects than in the middle, but the seeds do not exhibit anisotropic growth. Evidence suggests that citrate improves the stability of nanoplates bounded by large {111} facets by preventing diffusion to {111} facets.

Economic CO2 conversion to CO or syngas production requires product-selective, high-throughput, and durable electrolyzers. High-surface-area nanocatalysts combined with gas-diffusion layers (GDLs) enable high CO2 flux and conversion but can suffer from ineffective catalyst utilization, premature degradation, and flooding of the GDL that limit electrolyzer operation. Herein, a catalyst layer (CL) composed of a highly conductive catalyst bed of high-aspect-ratio Ag nanowire (Ag NW) electrocatalysts is integrated with a nonconductive porous polytetrafluorethylene (PTFE) GDL to enable more durable and selective electrolyzer performance. This platform enables exploration of CL thickness effects on catalyst utilization efficiency and selectivity. Combined with a 1-D computational model of the Ag NW-PTFE GDL, optimized CL thickness was found to be limited by significant depletion of local aqueous CO2 concentration, resulting in an optimal performance of 250 A/g (15× improvement) and a suppression of the hydrogen evolution reaction up to 20×. Furthermore, the local pH within the catalyst microenvironment indicates that local speciation of the bicarbonate electrolyte influences the selectivity between H2 and CO. Additional experimental measurements indicate that proton dissociation from bicarbonate contributes significantly to hydrogen evolution at intermediate overpotentials. The combination of a conductive and mechanically stable nanowire catalytic network with a hydrophobic PTFE porous support structure provides an effective platform for tuning the microenvironment of mesoscale catalysts for improved performance and durability during CO2 electroreduction.

An in situ formed hydrogel was synthesized by sodium alginate and cysteine methyl ester, which turned the sodium alginate into thiolated alginate (SA-SH). SA-SH can in situ formed into hydrogel (SA-SS-SA) with a large amount of water through covalent bond in less than 20 s. The structure characterization showed that the mechanism of SA-SH gelation was thiol-disulfide transformation. The rheology and cytotoxicity experiments of SA-SS-SA hydrogel were also investigated, which indicated that SA-SS-SA hydrogel had an appropriate mechanical strength as well as an excellent biocompatibility. The SA-SS-SA hydrogel would degrade under certain conditions after a few days and its mechanism was disulfide alkaline reduction. Finally, the hemostatic property of SA-SH was tested by rat tail amputation experiment. The time to hemostasis of rat reduced from 8.26 min to 3.24 min, which proved that SA-SH had an excellent hemostatic property.