The zinc‐metal anode (ZMA) is a critical component of rechargeable Zn‐based batteries. Zinc‐dendrite formation on ZMA during cycling causes an internal short‐circuit, thereby limiting long‐term practical operation of batteries. A strategy of introducing zincophilic sites shows promise in suppressing dendrite growth. However, the mechanism is not understood. Here, a detailed study of the mechanism of zincophilic sites based on multiple in situ/ex situ techniques is reported. Using a carbon‐host as a model system with nitrogen sites as zincophilic sites and both ex situ near‐edge X‐ray absorption fine structure (NEXAFS) and in situ Raman spectra, it is shown that zinc ions are bonded with pyridine sites to form ZnN bonds. The ZnN bonds induce spacious nucleation of zinc on carbon‐hosts and suppress zinc‐dendrite formation. The host with zincophilic sites exhibits a homogenous Zn deposition, together with boosted electrochemical performance. This finding underscores the impact of nitrogen zincophilic sites in suppressing zinc‐dendrite formation. It is shown that bonding between zinc ions and zincophilic sites is the mechanism for zincophilic nucleation in the ZMA host. These findings are expected to be of immediate benefit to researchers in battery technologies and materials science.
Perovskite solar cells (PSCs) are a promising photovoltaic technology for stretchable applications because of their flexible, light‐weight, and low‐cost characteristics. However, the fragility of crystals and poor crystallinity of perovskite on stretchable substrates results in performance loss. In fact, grain boundary defects are the “Achilles’ heel” of optoelectronic and mechanical stability. We incorporate a self‐healing polyurethane (s‐PU) with dynamic oxime–carbamate bonds as a scaffold into the perovskite films, which simultaneously enhances crystallinity and passivates the grain boundary of the perovskite films. The stretchable PSCs with s‐PU deliver a stabilized efficiency of 19.15 % with negligible hysteresis, which is comparable to the performance on rigid substrates. The PSCs can maintain over 90 % of their initial efficiency after 3000 hours in air because of their self‐encapsulating structure. Importantly, the self‐healing function of the s‐PU scaffold was verified in situ. The s‐PU can release mechanical stress and repair cracks at the grain boundary on multiple levels. The devices recover 88 % of their original efficiency after 1000 cycles at 20 % stretch. We believe that this ingenious growth strategy for crystalline semiconductors will facilitate development of flexible and stretchable electronics.
Monitoring and controlling the reconstruction of materials under working conditions is crucial for the precise identification of active sites,e lucidation of reaction mechanisms,and rational design of advanced catalysts.Herein, aBibased metal-organic framework (Bi-MOF) for electrochemical CO 2 reduction is selected as ac ase study.I ns itu Raman spectra combined with ex situ electron microscopyr eveal that the intricate reconstruction of the Bi-MOF can be controlled using two steps:1 )electrolyte-mediated dissociation and conversion of Bi-MOF to Bi 2 O 2 CO 3 ,a nd 2) potential-mediated reduction of Bi 2 O 2 CO 3 to Bi. The intentionally reconstructed Bi catalyst exhibits excellent activity,selectivity,and durability for formate production, and the unsaturated surface Bi atoms formed during reconstruction become the active sites.T his work emphasizes the significant impact of pre-catalyst reconstruction under working conditions and provides insight into the design of highly active and stable electrocatalysts through the regulation of these processes.
The translation of unparalleled efficiency from the lab-scale devices to practical-scale flexible modules affords a huge performance loss for flexible perovskite solar cells (PSCs). The degradation is attributed to the brittleness and discrepancy of perovskite crystal growth upon different substrates. Inspired by robust crystallization and flexible structure of vertebrae, herein, we employ a conductive and glued polymer between indium tin oxide and perovskite layers, which simultaneously facilitates oriented crystallization of perovskite and sticks the devices. With the results of experimental characterizations and theoretical simulations, this bionic interface layer accurately controls the crystallization and acts as an adhesive. The flexible PSCs achieve the power conversion efficiencies of 19.87% and 17.55% at effective areas of 1.01 cm 2 and 31.20 cm 2 respectively, retaining over 85% of original efficiency after 7000 narrow bending cycles with negligible angular dependence. Finally, the modules are assembled into a wearable solar-power source, enabling the upscaling of flexible electronics.
Copper is a significant platform for CO2 electroreduction catalysts because it is the only known metal to produce multi-carbon products but suffers from poor selectivity. In the early stages of the reaction pathway, a selectivity-determining step dictates if the pathway leads to formate (a dead-end) or to CO (and on to multi-carbon products). Therefore, controlling the adsorption of key intermediates, in order to steer the reaction pathway as desired, is critical for selective CO2 electroreduction. Alloying copper is a strategy in which the composition and electronic properties of the alloy surface can be finely tuned to alter the reaction intermediate adsorption behavior. Herein, through in situ Raman spectroscopy and density functional theory (DFT) calculations, we investigate a composition-dependent selectivity toward CO and formate during CO2 electroreduction on a range of Cu–Sn alloy catalysts. We find that the selectivity shifts from CO to formate generation as the Sn content in the alloy catalyst increases because of a shift in adsorption preference from the C-bound *COOH intermediate to the O-bound *OCHO intermediate. Theoretical DFT calculation results indicate that this selectivity shift is due to a gradual weakening of *COOH adsorption and strengthening of *OCHO that occurs with increasing Sn content. A combination of theoretical Bader charge analysis and experimental X-ray photoelectron spectroscopy revealed the origin of such transformation: upon alloying, charge is redistributed from Sn to Cu, which creates regions of localized positive charge on the Sn sites. Therefore, with increasing tin content, these localized positive sites hinder the nucleophilic attack of the CO2 carbon, making *COOH adsorption (and the CO pathway) less favorable.
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