A simple and low-cost polymer-aided sol–gel method was developed to prepare γ-Al2O3 protective layers for LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials. The selected polyvinyl alcohol polymer additive not only facilitates the formation of a uniform and thin γ-Al2O3 layer on the irregular and rough cathode particle surface to protect it from corrosion but also serves as a pore-forming agent to generate micropores in the film after sintering to allow fast transport of lithium ions, which guaranteed the excellent and stable battery performance at high working voltage. Detailed studies in the full battery mode showed that the leached corrosion species from the cathode had a more profound harmful effect to the graphite anode, which seemed to be the dominating factor that caused the battery performance decay.

In this work, we fabricate photodetectors made of methylammonium lead trihalide perovskite (MLHP) and phosphorus-doped graphitic carbon nitride nanosheets (PCN-S). Using thermal polymerization, PCN-S with a reduced band gap, are synthesized from low-cost precursors, making it feasible to form type-II bulk heterojunctions with perovskites. Owing to the bulk heterojunctions between PCN-S and MLHP, the dark current of the photodetectors significantly decreases from ∼10-9 A for perovskite-only devices to ∼10-11 A for heterojunction devices. As a result, not only does the on/off ratio of the hybrid devices increase from 103 to 105 but also the photodetectivity is enhanced by more than 1 order of magnitude (up to 1013 Jones) and the responsivity reaches a value of 14 A W-1. Moreover, the hybridization of MLHP with PCN-S significantly modifies the hydrophilicity and morphology of the perovskite films, which dramatically increases their stability under ambient conditions. The hybrid photodetectors, described here, present a promising new direction toward stable and efficient optoelectronic applications.

Although the electrochemical hydrogen evolution reaction (HER) on a Pt electrode is among the most studied electrocatalytic reactions, its reaction mechanism and exchange current density are still under debate. Particularly on the Pt catalyst, its facile reaction kinetics and lack of effective methods to compensate mass transport make it difficult to isolate kinetic and diffusion contributions. This study focuses on the quantitative description of mass transfer constraints arising from both H2 and phosphate buffer ions using a Pt electrocatalyst in near-neutral pH regions, which are overlooked in the literature despite the relevance to various (photo-) electrochemical reactions for water splitting and CO2 reduction. The established HER model that uses H+ as a reactant quantitatively breaks down the observed overpotentials with diffusion contributions of both hydrogen and buffer species while the intrinsic kinetics on Pt exhibits negligible contribution. The significance of electrolyte engineering, that is, the optimization of the electrolyte identity and molality, is confirmed to determine the overall HER performance. To maximize the HER performance on Pt at ambient temperature, the phosphate-buffer electrolyte should be adjusted to a pH close to pKa of the buffer that effectively minimizes the pH gradient and to the adequate molality of the buffer (typically ∼0.5 M phosphates) that H2 diffusion is maximized, which is related with H2 solubility and solution viscosity. At pH far from pKa, concentration overpotential of buffer ion dominates the overall performance, which requires highly dense buffer (>1.5 M phosphates) to minimize the pH gradient.

Mo/ZSM-5 is one of the most studied and efficient catalysts for the dehydroaromatization of methane (MDA), but the mechanism of its operation remains controversial. Here, we combine an ab initio thermodynamic analysis with a comprehensive mechanistic density functional theory study to address Mo-speciation in the zeolite and identify the active sites under the reaction conditions. We show that the exposure of Mo/ZSM-5 to the MDA conditions yields a range of reduced sites including mono- and binuclear Mo-oxo and Mo-carbide complexes. These sites can catalyze the MDA reaction via two alternative reaction channels, namely, the C-C coupling (ethylene) and the hydrocarbon-pool propagation mechanisms. Our calculations point toward the binuclear Mo-carbide species operating through the hydrocarbon-pool mechanism to be the most catalytically potent species. Although all other Mo sites in the activated catalyst can promote C-H activation in methane, they fail to provide a successful path to the desirable low-molecular-weight products.

Selective hydroamination of terminal alkynes with primary aryl amines is catalyzed by an unprecedented well-defined silica-supported tantalum complex [(≡Si-O-)Ta(η1σ-NEtMe)2(=NtBu)]. A molecular-level characterization of the surface organometallic Ta species was done with the help of characterization tech-niques including as in situ infrared, in situ elemental microanal-ysis, 1H and 13C solid-state NMR (including double and triple quanta sequence), and X-ray absorption spectroscopies. These were complemented by the state-of-the-art DNP-SENS 15N characterization. Several catalytic intermediates have been isolated in particular the 4-membered metallacycle ring inter-mediate resulting from the anti Markovnikov addition of the alkyne to the surface tantalum imido. The mechanism proposed was based on the isolation of all intermediates. A DFT calcula-tion has confirmed all the elementary steps and intermediates that were fully characterized.

e report the preparation and electrocatalytic performance of silver-containing gas diffusion electrodes (GDEs) derived from a silver coordination polymer (Ag-CP). Layer-by-layer growth of the Ag-CP onto porous supports was applied to control Ag loading. Subsequent electro-decomposition of the Ag-CP resulted in highly selective and efficient CO2-to-CO GDEs in aqueous CO2 electroreduction. Afterward, the metal–organic framework (MOF)-mediated approach was transferred to a gas-fed flow electrolyzer for high current density tests. The in situ formed GDE, with a low silver loading of 0.2 mg cm–2, showed a peak performance of jCO ≈ 385 mA cm–2 at around −1.0 V vs RHE and stable operation with high FECO (>96%) at jTotal = 300 mA cm–2 over a 4 h run. These results demonstrate that the MOF-mediated approach offers a facile route for manufacturing uniformly dispersed Ag catalysts for CO2 electrochemical reduction by eliminating ill-defined deposition steps (drop-casting, etc.) while allowing control of the catalyst structure through self-assembly.

Tadpole polymers are excellent candidates to explore how architecture can influence self-assembly because they combine two topologies in the same molecule (ring polymer as the head and linear polymer as the tail). In this work, we synthesize well-defined tadpole homo-/co-/terpolymers derived from the appropriate chemical modification reactions of the corresponding 3-miktoarm star homo-/co-/terpolymers via anionic polymerization, high vacuum techniques, and chlorosilane chemistry in combination with the Glaser coupling reaction. The 3-miktoarm star homo-/co-/terpolymers bear two arms with t-butyl dimethylsiloxypropyl functional end-groups, whereas after deprotection, the ω-hydroxyl chain-ends were modified to alkyne moieties. The dialkyne star polymers in the presence of Cu(I)Br and N,N,N′,N″,N″-pentamethyldiethylenetriamine were then transformed to well-defined tadpole homo-/co-/terpolymers. We employed strongly immiscible blocks to enable characterization using electron microscopy and X-ray scattering to explore how the molecular topology influences the self-assembled bulk-state microdomain morphologies.

Polysilicon passivating contacts, consisting of a stack of tunnel-oxide and doped polysilicon layers, can simultaneously provide excellent surface passivation and low contact resistivity for silicon solar cells. Nevertheless, the microscopic interfacial characteristics of such contacts are not yet fully understood. In this work, by investigating the surface passivation evolution of polysilicon passivating contacts under increasing annealing temperatures, we unveil these characteristics. Before annealing, we find that the Si and O atoms within the tunnel-oxide layer are mostly unsaturated, whereas the O atoms introduce acceptor-like defects. These defects cause Fermi-level pinning and high carrier recombination. During annealing, we identify two distinct chemical passivation regimes driven by surface hydrogenation and oxidation. We attribute the excellent chemical passivation activated by high-temperature annealing (∼850 °C) mainly to the tunnel oxide reconstruction, which effectively reduces the acceptor-like state density. During the oxide reconstruction, we also find that subnanometer pits (rather than pinholes) are formed in the oxide. A combination of experimental and theoretical investigations demonstrates these subnanometer pits provide excellent surface passivation and efficient tunneling for majority carriers.

The direct hydrogenation of CO2 to methanol using hydrogen is regarded as a potential technology to reduce greenhouse gas emissions and the dependence on fossil fuels. For this technology to become feasible, highly selective and productive catalysts that can operate under a wide range of reaction conditions near thermodynamic conversion are required. Here we combine a CO-producing In oxide catalyst with a methane-producing Co catalyst to obtain an In/Co catalyst for CO2 reduction to methanol. Density functional (DFT) simulations demonstrate that the charge transfer between the Co support and the In oxide film leads to enrichment of the surface of indium oxide with O vacancies, which serve as active sites for selective conversion of CO2 to methanol. Moreover, our simulations suggest that CO2 reduction on Co-supported In2O3–x films will preferentially yield methanol, rather than CO and methane. As a result, the prepared In@Co catalysts produce methanol from CO2 with high selectivity (>80%) and productivity (0.86 gCH3OH gcatalyst–1 h–1) at conversion levels close to thermodynamic equilibrium, even at temperatures as high as 300 °C and at moderate pressures (50 bar).

The superoxide (O2•-) ion is a highly reactive oxygen species involved in many diseases; hence, its noninvasive detection is desirable to identify the onset of pathological processes. Here, we employed photoacoustic (PA) spectroscopy, which enables imaging at ultrasound resolution with the sensitivity of optical modality, for the first time to detect O2•-, using stimuli-responsive contrast agents. meso-(3,5-Di-tert-butyl 4-hydroxyphenyl) porphyrins and oxoporphyrinogens were used as PA contrast agents, which trap the O2•- and enable its detection. The trapped O2•- increased the PA signal amplitude of chromophores up to 9.6-fold, and induced a red-shift in the PA signal maxima of up to 225 nm. Therefore, these trigger-responsive probes may be highly valuable as smart diagnostic PA probes to investigate pathological events stimulated by O2•- species.