Potassium-Ion Oxygen Battery Based on a High Capacity Antimony Anode

Recent investigations into the application of potassium in the form of potassium–oxygen, potassium–sulfur, and potassium-ion batteries represent a new approach to moving beyond current lithium-ion technology. Herein, we report on a high capacity anode material for use in potassium–oxygen and potassium-ion batteries. An antimony-based electrode exhibits a reversible storage capacity of 650 mAh/g (98% of theoretical capacity, 660 mAh/g) corresponding to the formation of a cubic K₃Sb alloy. The Sb electrode can cycle for over 50 cycles at a capacity of 250 mAh/g, which is one of the highest reported capacities for a potassium-ion anode material. X-ray diffraction and galvanostatic techniques were used to study the alloy structure and cycling performance, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy were used to provide insight into the thermodynamics and kinetics of the K–Sb alloying reaction. Finally, we explore the application of this anode material in the form of a K₃Sb–O₂ cell which displays relatively high operating voltages, low overpotentials, increased safety, and interfacial stability, effectively demonstrating its applicability to the field of metal oxygen batteries

Membrane-Inspired Acidically Stable Dye-Sensitized Photocathode for Solar Fuel Production

Tandem dye-sensitized photoelectrochemical cells (DSPECs) for water splitting are a promising method for sustainable energy conversion but so far have been limited by their lack of aqueous stability and photocurrent mismatch between the cathode and anode. In nature, membrane-enabled subcellular compartmentation is a general approach to control local chemical environments in the cell. The hydrophobic tails of the lipid make the bilayer impermeable to ions and hydrophilic molecules. Herein we report the use of an organic donor–acceptor dye that prevents both dye desorption and semiconductor degradation by mimicking the hydrophobic/hydrophilic properties of lipid bilayer membranes. The dual-functional photosensitizer (denoted as BH4) allows for efficient light harvesting while also protecting the semiconductor surface from protons and water via its hydrophobic π linker. The protection afforded by this membrane-mimicking dye gives this system excellent stability in extremely acidic (pH 0) conditions. The acidic stability also allows for the use of cubane molybdenum-sulfide cluster as the hydrogen evolution reaction (HER) catalyst. This system produces a proton-reducing current of 183 ± 36 μA/cm² (0 V vs NHE with 300 W Xe lamp) for an unprecedented 16 h with no degradation. These results introduce a method for developing high-current, low-pH DSPECs and are a significant move toward practical dye-sensitized solar fuel production

Probing the Low Fill Factor of NiO p‑Type Dye-Sensitized Solar Cells

p-Type dye-sensitized solar cells (<i>p</i>-DSCs) have attracted increasing attention recently, but they suffer from low fill factors (FFs) and unsatisfactory efficiencies. A full comprehension of the hole transport and recombination processes in the NiO <i>p</i>-DSC is of paramount importance for both the fundamental study and the practical device optimization. In this article, NiO <i>p</i>-DSCs were systematically probed under various bias and illumination conditions using electrochemical impedance spectroscopy (EIS), intensity modulated photocurrent spectroscopy (IMPS), and intensity modulated photovoltage spectroscopy (IMVS). Under the constant 1 sun illumination, the recombination resistance (<i>R</i>_rec) of the cell deviates from an exponential relationship with the potential and saturates at ∼130 Ω cm² under the short circuit condition, which is ascribed to the overwhelming recombination with the reduced dye anions. Such a small <i>R</i>_rec results in the small dc resistance, which decreases the “flatness” of the <i>J–V</i> curve. The quantitative analysis demonstrates that the FF value is largely attenuated by the recombination of holes in NiO with the reduced dyes. Our analysis also shows that if this recombination can be eliminated, then an FF value of 0.6 can be reached, which agrees with the theoretical calculation with a <i>V</i>_oc of 160 mV

Synthesis, Photophysics, and Photovoltaic Studies of Ruthenium Cyclometalated Complexes as Sensitizers for p‑Type NiO Dye-Sensitized Solar Cells

We report the first application of cyclometalated ruthenium complexes of the type Ru­[(N^∧N)₂(C^∧N)]⁺ as sensitizers for p-type NiO dye-sensitized solar cells (NiO p-DSCs). These dyes exhibit broad absorption in the visible region. The carboxylic anchoring group is attached to the phenylpyridine ligand, which results in efficient hole injection. Moreover, the distance between the Ru­[(N^∧N)₂(C^∧N)]⁺ core and the carboxylic anchoring group is systematically varied by inserting rigid phenylene linkers. Femtosecond transient absorption (TA) studies reveal that the interfacial charge recombination rate between reduced sensitizers and holes in the valence band of NiO decreases as the number of phenylene linkers increases across the series. As a result, the solar cell made of the dye with the longest spacer (O12) exhibits the highest efficiency with both increased short-circuit current (<i>J</i>_sc) and open-circuit voltage (<i>V</i>_oc). The incident photon-to-current conversion efficiency (IPCE) spectra match well with the absorption spectra of sensitizers, suggesting the observed cathodic current is generated from the dye sensitization. In addition, the absorbed photon-to-current conversion efficiencies (APCEs) display an increment across the series. We further studied the interfacial charge recombination of our solar cells by electrochemical impedance spectroscopy (EIS). The results reveal an enhanced hole lifetime as the number of phenylene linkers increases. This study opens up opportunities of using cyclometalated Ru complexes for p-DSCs

Tunable Molecular MoS₂ Edge-Site Mimics for Catalytic Hydrogen Production

Molybdenum sulfides represent state-of-the-art, non-platinum electrocatalysts for the hydrogen evolution reaction (HER). According to the Sabatier principle, the hydrogen binding strength to the edge active sites should be neither too strong nor too weak. Therefore, it is of interest to develop a molecular motif that mimics the catalytic sites structurally and possesses tunable electronic properties that influence the hydrogen binding strength. Furthermore, molecular mimics will be important for providing mechanistic insight toward the HER with molybdenum sulfide catalysts. In this work, a modular method to tune the catalytic properties of the S–S bond in MoO­(S₂)₂L₂ complexes is described. We studied the homogeneous electrocatalytic hydrogen production performance metrics of three catalysts with different bipyridine substitutions. By varying the electron-donating abilities, we present the first demonstration of using the ligand to tune the catalytic properties of the S–S bond in molecular MoS₂ edge-site mimics. This work can shed light on the relationship between the structure and electrocatalytic activity of molecular MoS₂ catalysts and thus is of broad importance from catalytic hydrogen production to biological enzyme functions

Tunable Molecular MoS₂ Edge-Site Mimics for Catalytic Hydrogen Production

Molybdenum sulfides represent state-of-the-art, non-platinum electrocatalysts for the hydrogen evolution reaction (HER). According to the Sabatier principle, the hydrogen binding strength to the edge active sites should be neither too strong nor too weak. Therefore, it is of interest to develop a molecular motif that mimics the catalytic sites structurally and possesses tunable electronic properties that influence the hydrogen binding strength. Furthermore, molecular mimics will be important for providing mechanistic insight toward the HER with molybdenum sulfide catalysts. In this work, a modular method to tune the catalytic properties of the S–S bond in MoO­(S₂)₂L₂ complexes is described. We studied the homogeneous electrocatalytic hydrogen production performance metrics of three catalysts with different bipyridine substitutions. By varying the electron-donating abilities, we present the first demonstration of using the ligand to tune the catalytic properties of the S–S bond in molecular MoS₂ edge-site mimics. This work can shed light on the relationship between the structure and electrocatalytic activity of molecular MoS₂ catalysts and thus is of broad importance from catalytic hydrogen production to biological enzyme functions

Tunable Molecular MoS₂ Edge-Site Mimics for Catalytic Hydrogen Production

Molybdenum sulfides represent state-of-the-art, non-platinum electrocatalysts for the hydrogen evolution reaction (HER). According to the Sabatier principle, the hydrogen binding strength to the edge active sites should be neither too strong nor too weak. Therefore, it is of interest to develop a molecular motif that mimics the catalytic sites structurally and possesses tunable electronic properties that influence the hydrogen binding strength. Furthermore, molecular mimics will be important for providing mechanistic insight toward the HER with molybdenum sulfide catalysts. In this work, a modular method to tune the catalytic properties of the S–S bond in MoO­(S₂)₂L₂ complexes is described. We studied the homogeneous electrocatalytic hydrogen production performance metrics of three catalysts with different bipyridine substitutions. By varying the electron-donating abilities, we present the first demonstration of using the ligand to tune the catalytic properties of the S–S bond in molecular MoS₂ edge-site mimics. This work can shed light on the relationship between the structure and electrocatalytic activity of molecular MoS₂ catalysts and thus is of broad importance from catalytic hydrogen production to biological enzyme functions