ACS Energy Letters 最新文献

The identity of electrolyte cations has an important influence on the rates of many electrocatalytic reactions, but these effects are not always observed. Recently, we found that the surface charge of the catalyst, quantified by the potential of zero total charge (PZTC), is a useful heuristic for predicting when cation effects will be observed for the oxygen reduction reaction (ORR). Here, we demonstrate that this descriptor allows us to rationalize the observation or absence of cation effects across a range of conditions, reactions (the hydrogen evolution reaction, the ORR, methanol oxidation, ethylene glycol oxidation, glycerol oxidation, and glucose reduction) and metal surfaces (Pt, Pd, Ag, and Au). These results suggest that when the reaction’s operating potential is negative of the metal’s PZTC, electrolyte cations accumulate at the catalyst surface and influence reaction rates. When reactions occur positive of the PZTC, cation effects are not observed.

The operational stability of perovskite solar cells is limited by defects and instabilities at grain boundaries and buried interfaces in three-dimensional absorbers. Forming 3D/low-dimensional (LD) heterojunctions can improve both efficiency and durability, yet most LD layers use ammonium ligands that bind weakly to the lattice and can deprotonate, causing the LD layer to degrade under heat and illumination. This Perspective highlights amidinium-based organic ligands as a promising alternative for constructing more robust LD capping layers. Their planar, multivalent, resonance-stabilized headgroups enable stronger lattice interactions and reduced deprotonation. Although still emerging, tailoring the ligand tail provides a versatile handle to tune dimensionality, interfacial energetics, strain, and electronic coupling toward efficient, stable LD perovskite heterojunction photovoltaics.

Mixed halide perovskites often undergo reversible phase segregation under illumination, yet the exact underlying mechanism and the material properties affecting this process remain unclear. By combining time-resolved photoluminescence (TRPL) with in situ X-ray diffraction (XRD) under illumination, we show that segregation kinetics and the thermodynamic limit of segregation under illumination in MAPbI_1.5Br_1.5 are not intrinsically linked. The segregation rate increases linearly with the defect density inferred from TRPL. In contrast, the equilibrium extent of segregation is independent of defect density but instead decreases with reducing crystallite size down to a critical, finite-size threshold of ∼40 nm, below which segregation is suppressed. Defect passivation using the ionic liquid BMIMBF₄ slows the segregation kinetics but does not affect equilibrium limits. These findings establish crystallite size as a thermodynamic constraint and defects as kinetic mediators, outlining considerations for designing photostable mixed halide perovskites.

Electrochemical carbon capture based on an interfacial high-pH microenvironment represents a significant advancement in carbon capture technologies; however, its design remains constrained by limited carbon mass diffusion within the ultrathin catalyst layer, particularly in direct air capture (DAC) applications. Here, we demonstrated a practical approach to enhance interfacial CO₂ mass transport through the implementation of an extended absorption layer (EAL) design. By incorporating the EAL into a porous solid electrolyte (PSE) reactor performing oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) redox electrolysis, we achieved a seven-fold increase in both electron efficiency (10 mA cm^–2, 28%) and CO₂ capture rate (0.7 × 10^–3 mL s^–1 cm^–2) for the DAC process. Stable operation of more than 35 days and continuous production of near-saturated carbonated water solely from indoor air were demonstrated in our device, indicating its practical applicability.

Surface-area normalization is essential for quantitative comparison in electrochemistry, yet ambiguity in what area represents hampers interpretation and reproducibility. We distinguish the real surface area, a geometric measure of surface roughness and structure, from the electrochemically active surface area, defined as the condition-dependent subset of surface sites participating in a specific faradaic reaction. We clarify how double-layer capacitance and adsorption-limited charge-transfer reactions probe different regions of the electrode surface and how their interpretation and reference values determine whether the result corresponds to an apparent area, the real surface area, or the electrochemically active surface area. We further show that commonly used reference values vary strongly with electrode structure, electrolyte composition, and measurement protocol. To address this, we introduce a formalism based on domain-specific linear combinations of surface contributions that enables structurally consistent area estimates. Finally, we propose normalizing current by active-site count as a direct and reproducible measure of intrinsic activity.

Quasi-solid-state-polymer-electrolyte-based (QSSE-based) quasi-solid-state lithium–sulfur batteries (QSSLSBs) are an emerging research focus because they are safe and deliver high energy density. However, sluggish interfacial reaction kinetics involving the sulfur cathode and QSSE remains a core developmental bottleneck. Herein, we reveal that the cations and anions of tetrabutylammonium iodide (TBAI) promote S₃^•– generation via a synergistic electrostatic–nucleophilic catalysis mechanism that accelerates lithium polysulfide conversion. Accordingly, we innovatively introduced TBAI into the cathode–QSSE interface to construct an QSSE with a catalytically active interfacial layer that realized enhanced interface reaction kinetics. The cycling performance of the assembled QSSLSBs: an average decay rate of only 0.038% per cycle over 1600 stable long cycles at 0.2 C; a capacity retention of 70.5% after 100 cycles at 0.1 C under a high sulfur loading of 6.5 mg·cm^–2. The synergistic electrostatic–nucleophilic catalysis strategy developed herein provides innovative insight that addresses the sluggish interfacial kinetics of the QSSLSB cathode.

Dendrite formation at elevated current densities presents a major challenge for aqueous zinc-ion batteries (AZIBs), necessitating a deep mechanistic understanding. We investigate dendrite growth in Zn symmetric cells under stringent conditions (20 mA cm^–2 and 20 mAh cm^–2) in a 2 M ZnSO₄ electrolyte. Our analysis reveals zinc carbonate and Zn₄SO₄(OH)₆·5H₂O in the solid electrolyte interphase (SEI), due to dissolved CO₂, initiating dendritic growth and leading to rapid short-circuit within 40 h. In contrast, trace propylene carbonate (PC) stabilizes CO₂, promoting a homogeneous, carbonate-free SEI layer and extending cycle life over 420 h. Moreover, cross-sectional electron backscatter diffraction (EBSD) analysis of the failed electrode demonstrates that the Zn dendrites grow with no epitaxial relationship to the substrate. The Zn//MnO₂ full cell with PC-modified electrolyte maintains a capacity of 203 mAh g^–1 after 1000 cycles at 2 C, elucidating Zn dendrite formation mechanisms and guiding electrolyte and anode optimization for AZIBs.

Achieving reversible sodium metal plating and stripping is essential for enabling practical Na metal batteries but remains limited by unstable electrolyte–metal interphases. Here, we quantitatively examine how solvation thermodynamics, interfacial kinetics, ion transport, and solid electrolyte interphase (SEI) composition govern Na metal reversibility in sodium bis(fluorosulfonyl)imide (NaFSI) electrolytes with 1,2-dimethoxyethane (DME), fluoroethylene carbonate (FEC), and N,N-dimethylsulfamoyl fluoride (DMFSA). Unlike Li systems, Na metal Coulombic efficiency (CE) shows no correlation with either the Na⁺/Na redox potential or the interfacial reaction entropy. Instead, increased CE in electrolytes like 1 M sodium hexafluorophosphate in DME corresponds to faster interfacial kinetics relative to ion diffusivity (j₀^SEI/FcD). X-ray photoelectron spectroscopy highlights the importance of balancing the inorganic and organic SEI phases to optimize interfacial kinetics and CE. These results establish interfacial kinetics, rather than solvation thermodynamics, as a governing descriptor of Na metal reversibility, providing an electrolyte design framework for improving Na metal batteries.

Electrochemical reactions occur at charged interfaces where the accumulation and redistribution of charge within the electric double layer (EDL) fundamentally govern the reaction kinetics. Despite its ubiquity, the mechanistic connection between EDL charging and electrocatalytic activity remains underexplored. This Perspective highlights recent theoretical and experimental advances─focusing on studies from our group and others─that link the degree of EDL charging, characterized by the surface charge density (σ), to catalytic activity. We categorized the types of charge accumulated in the EDL as space charge, ionic charge, and pseudocapacitive charge and discussed how these components mechanistically influence electrocatalytic activity. Together, these insights suggest σ as a key descriptor that representatively captures the microenvironment effect of the EDL, bridging interfacial charge dynamics and catalytic performance and thereby suggesting new opportunities for the rational design of high-performance electrochemical interfaces.

The local pH environment within bipolar membrane (BPM) junctions is complex and not well understood, yet it is important to control for advancing the performance of BPM-based electrochemical systems. We report a voltammetric strategy using an ultrathin Ni mesh pH probe to spatially resolve pH changes in the BPM junction during model BPM electrolyzer operation. Under reverse bias, we observe depletion of OH^– at the anion-exchange layer (AEL) interface, with a degree diminishing with increasing distance from the AEL. These gradients correlate with current-dependent water dissociation (WD) and are modulated by the electric field and the surface charge state of the catalyst. By correlating spatial pH profiles with the surface-charging behavior of WD catalysts, we explore a mechanism of catalyst-mediated H⁺ and OH^– transfer facilitated by hydrogen-bonding networks. These findings highlight the role of local chemistry and electrostatics in BPM performance and offer new methods to probe and engineer catalytic junctions in electrochemical energy devices.