ACS Energy Letters 最新文献

Electro-oxidation of CO is a common kinetic bottleneck in many types of fuel cells and organic electrosynthesis processes. Alloys of Pt and Ru are often used as anode catalysts, with high activity attributed to bifunctionality; this suggests that Ru preferentially activates water to form surface hydroxyl groups that can react with Pt-bound CO. However, rigorous kinetic measurements have not confirmed this assertion under steady-state electro-oxidation conditions. Here, CO electro-oxidation is analyzed using several commercial Pt/C and Pt_100-xRu_x/C nanoparticle catalysts in acidic and alkaline electrolytes. Kinetic observables including apparent transfer coefficients and reaction orders are measured and evaluated using a degree of rate control analysis. The kinetic observables for both Pt and PtRu alloys are most consistent with competitive adsorption and Langmuir–Hinshelwood coupling across a single site-type, rather than two distinct sites. Therefore, the role of Ru in CO electro-oxidation is assigned to be a purely electronic effect.

Lead halide perovskite nanocrystals (NCs) are promising materials for light-emitting diodes (LEDs) due to their wavelength tunability, narrow emission line width, and high photoluminescence quantum yield. Oftentimes, these devices suffer from charge carrier imbalance and reduced charge injection because as-synthesized NCs are covered by long aliphatic ligands. Here, we report ligand exchange to small electron-withdrawing or -donating cinnamate ligands. We probe the influences of the ligands’ inductive effect on hole injection by photoluminescence spectroelectrochemistry (PL SEC). We find that hole injection into NCs covered by electron-withdrawing ligands is facilitated, and hole-only devices exhibit higher currents compared to electron donating ligands. Our work highlights the potential of PL SEC as a powerful tool to rationalize the performance of lead halide perovskite NCs in LEDs.

Enabling a nonexpensive, highly active, and durable anion exchange membrane water electrolyzer (AEMWE) promises to meet the surging energy demand reducing the carbon footprint. Their major discrepancy is the poor durability of the oxidation compartment with a less-durable catalyst and electrode-support assembly. Unlike efficient expensive catalysts IrO₂ and RuO₂ in proton exchange membrane water electrolyzer, the anion-exchange ones use inexpensive 3d-transition-metal-based compounds as the anode electrocatalysts. These catalysts are poorly stable at ampere-level current density, because of metal leaching, surface passivation/insulation, mechanical instability, carbon-substrate degradation, side reactions by leached metal damaging the membrane, alkaline and oxidative degradation of the ionomer, and insufficient mass transfer due to poor bubble dynamics in alkaline media. Besides efficient material design, there are various other parameters that govern the electrolyzers’ longevity. This perspective focuses on the understanding and directions to solve each above-mentioned problem to attain more stable, durable, and highly active AEMWEs.

Selective electrochemical reduction of CO₂ (CO₂RR) to CO represents an opportunity to convert a waste product into a useful reactant with a near-term technoeconomic viability. The electrolytes applied in the CO₂ electrolyzers strongly affect their performance through cationic activation of interfacial CO₂ and H₂O in the electric double layer (EDL). In this work, we demonstrate an electrolyte design strategy that leverages Al³⁺ complexation with tartrate^2– to form stable solutions in a HCO₃^– buffer, improving the selectivity of the CO production and activity on Au. We also find that tartrate^2– significantly reduces the onset of hydrogen evolution, even in the absence of Al³⁺. Ab-initio molecular dynamics (AIMD) simulations reveal that interfacial tartrate^2– polarize H₂O away from the negatively polarized Au electrode and that Al³⁺ induces greater activation of *CO₂ than K⁺. Hence, the rate limiting steps for the hydrogen evolution reaction (HER) and the CO₂RR are slowed by tartrate^2– and accelerated by Al³⁺. This work demonstrates electrolyte design beyond standard alkali metal solutions to further improve the CO₂RR selectivity.

Interfacial band alignment in two-dimensional (2D)/three-dimensional (3D) perovskite heterostructures is crucial for maximizing separation, extraction, and collection of charge carriers, which, in turn, stabilize the perovskite layer during solar cell operation. Despite the wide use of 2D spacer cations for stabilizing perovskite solar cells, spacer cation exchange across the 2D/3D interface induces structural transformation and degradation in performance and stability. We have now examined the electrochemical and photoelectrochemical behavior of 2D Ruddlesden–Popper (RP) and Dion–Jacobson (DJ) perovskites to assess the impact of binding configuration on the interfacial charge separation and their operational stability. In-situ open circuit potential (OCP) responses of 2D perovskites under light illumination, paired with redox couples (ferrocene/ferrocenium), reveal different semiconducting polarizabilities of BA-RP (n-type) and BDA-DJ (p-type). The tunability of the Fermi energy level in 2D perovskites discussed in this study offers insight into the design of 2D/3D interfaces for optimizing charge transfer and enhancing charge neutrality and stability.

Thermal quenching (TQ) generally occurs in phosphors and is ascribed to the activation of nonradiative transitions at elevated temperatures. This effect limits the use of most phosphors in high-power/high-temperature applications, such as outdoor lighting and laser systems. To achieve anti-TQ properties, structural design of phosphors is required. This usually follows two guidelines: (1) increasing lattice rigidity to minimize thermal expansion; (2) converting thermal energy into radiative transitions to compensate for the nonradiative losses. While metal oxides and metal nitrides dominate the field of commercial anti-TQ phosphors, metal halides, despite their inherently soft lattices, have shown remarkable progress as anti-TQ phosphors in recent years. Here, we review the advances in anti-TQ metal halides (covering the time span from 2017, when the first reports appeared, until today) and discuss their mechanisms and applications. We argue that the low synthesis temperatures of metal halides and their high photoluminescence quantum yields (PLQYs) make them promising candidates as anti-TQ phosphors. Furthermore, since the rich optical–physical processes underlying the anti-TQ effect in soft-lattice in metal halides are only now beginning to be unraveled, this creates opportunities for many fundamental investigations.

Wide-bandgap (WBG) perovskite solar cells (PSCs, E_g ≃ 1.67 eV) still suffer from pronounced open-circuit-voltage (V_OC) deficits. Here, we report a synergistic surface-passivation strategy that coassembles a dipolar quaternary-ammonium salt, acetylcholine chloride (ACCl), with an electron-rich long-chain alkylammonium halide, n-octylammonium iodide (OAI). A mixed ACCl:OAI treatment reconstructs the perovskite surface, lowers surface-trap density, and aligns the valence band with the hole-transport layer. Consequently, the champion WBG PSC delivers V_OC = 1.29 V, J_SC = 20.0 mA cm^–2, FF = 82.8%, and PCE = 21.27%, corresponding to 92.8% of the Shockley–Queisser voltage limit. When integrated as the top absorber in a monolithic n-i-p perovskite/p-type Si tandem, the passivated WBG cell contributed to a PCE of 26.8% with a V_OC of 1.91 V. These results reveal that cooperative defect passivation and energy-level engineering are both essential to unlock the full voltage potential of WBG perovskites.

Colloidal quantum dots (QDs) exhibit exceptional triplet sensitization capabilities for near-infrared (NIR)-to-visible photon upconversion (UC) via triplet–triplet annihilation (TTA). Although eco-friendly lead-free QDs hold promise as NIR sensitizers, the development of NIR Ag-based QD TTA-UC system remains in its infancy. In this work, we employ AgAuSe QDs as NIR-harvesting sensitizers and demonstrate that surface ligands dictate the feasibility of triplet energy transfer (TET). Thiol ligands are essential for passivating QD surface to achieve high quantum yield, while their strong affinity with Ag⁺ and Au⁺ in AgAuSe QDs inhibits the binding of triplet energy transmitter molecules, thereby preventing TET. In contrast, amine-capped AgAuSe QDs enable efficient TET, achieving an upconversion efficiency of 21.5% (normalized to 100%). Moreover, our strategy is universally applicable to NIR-to-visible UC using other Ag-based QDs such as Ag₂S. These findings overcome a critical bottleneck that has impeded TET in Ag-based QDs, thereby unlocking their potential for a new generation of UC materials.

Perovskite solar cells (PSCs) have achieved remarkable progress through suppressing nonradiative recombination via surface and bulk treatment. However, randomly integrating surface and bulk treatments mutually interfere with their functions, limiting the superposed efficacy in defect mitigation. Herein, we present a spatially complementary multiscale defect-management strategy through the selective integration of cesium trifluoroacetate (CsTFA) additives with phenethylammonium bromide (PEABr) surface treatments. Driven by top-down crystallization of perovskite films, CsTFA preferentially migrates to the bottom region of the perovskite film, eliminating the unexpected interference with the top surface ligands. CsTFA suppresses bulk defects through Pb²⁺-carbonyl coordination and hydrogen bonding, while a formed two-dimensional (PEA)₂PbI₄ top capping layer terminates the surface dangling bonds. This synergistic strategy yields perovskite films with reduced defects and extended carrier lifetimes. The optimized devices demonstrate the power conversion efficiency (PCE) of 25.84% with enhanced stability, maintaining 84.46% of the initial efficiency under ambient conditions for 2000 h.