Atomic-engineered gradient tunable solid-state metamaterials.

Metamaterial has been captivated a popular notion, offering photonic functionalities beyond the capabilities of natural materials. Its desirable functionality primarily relies on well-controlled conditions such as structural resonance, dispersion, geometry, filling fraction, external actuation, etc. However, its fundamental building blocks-meta-atoms-still rely on naturally occurring substances.

Closed-Loop Multi-Objective Optimization for Cu-Sb-S Photo-Electrocatalytic Materials' Discovery.

Copper antimony sulfides are regarded as promising catalysts for photo-electrochemical water splitting because of their earth abundance and broad light absorption. The unique photoactivity of copper antimony sulfides is dependent on their various crystalline structures and atomic compositions. Here, a closed-loop workflow is built, which explores Cu-Sb-S compositional space to optimize its photo-electrocatalytic hydrogen evolution from water, by integrating a high-throughput robotic platform, characterization techniques, and machine learning (ML) optimization workflow.

Machine learning-assisted optimization of multi-metal hydroxide electrocatalysts for overall water splitting.

Green hydrogen produced electrochemical water splitting is a suitable candidate to replace emission-intensive fuels. However, the successful widespread adoption of green hydrogen is contingent on the development of low-cost, earth-abundant catalysts. Herein, machine learning models built on experimental data were used to optimize the precursor ratios of hydroxide-based electrocatalysts, with the objective of improving the product's electrocatalytic performance for overall water splitting.

Sub-10 nm Mixing and Alloying of Cu-Ag and Cu-Ni via Accelerated Solid Diffusion.

Development of nanoscale multicomponent solid inorganic materials is often hindered by slow solid diffusion kinetics and poor precursor mixing in conventional solid-state synthesis. These shortcomings can be alleviated by combining nanosized precursor mixtures and low temperature reaction, which could reduce crystal growth and accelerate the solid diffusion at the same time. However, high throughput production of nanoparticle mixtures with tunable composition via conventional synthesis is very challenging.

Surface charge as activity descriptors for electrochemical CO reduction to multi-carbon products on organic-functionalised Cu.

Intensive research in electrochemical CO reduction reaction has resulted in the discovery of numerous high-performance catalysts selective to multi-carbon products, with most of these catalysts still being purely transition metal based. Herein, we present high and stable multi-carbon products selectivity of up to 76.6% across a wide potential range of 1 V on histidine-functionalised Cu.

High-Performance NiS Hollow Nanosphere Cathodes in Magnesium-Ion Batteries Enabled by Tunable Redox Chemistry.

Two-dimensional metal dichalcogenides have demonstrated outstanding potential as cathodes for magnesium-ion batteries. However, the limited capacity, poor cycling stability, and severe electrode pulverization, resulting from lack of void space for expansion, impede their further development. In this work, we report for the first time, nickel sulfide (NiS) hollow nanospheres assembled with nanoparticles for use as cathode materials in magnesium-ion batteries.

Polaron Delocalization Dependence of the Conductivity and the Seebeck Coefficient in Doped Conjugated Polymers.

Conjugated polymers are promising materials for thermoelectrics as they offer good performances at near ambient temperatures. The current focus on polymer thermoelectric research mainly targets a higher power factor (PF; a product of the conductivity and square of the Seebeck coefficient) through improving the charge mobility. This is usually accomplished structural modification in conjugated polymers using different processing techniques and doping.

Sulfurized Cyclopentadienyl Nanocomposites for Shuttle-Free Room-Temperature Sodium-Sulfur Batteries.

A major challenge hindering the practical adoption of room-temperature sodium-sulfur batteries (NaSBs) is polysulfide dissolution and shuttling, which results in irreversible capacity decay and low Coulombic efficiencies. In this work, we demonstrate for the first time NaSBs using a ferrocene-derived amorphous sulfurized cyclopentadienyl composite (SCC) cathode. Polysulfide dissolution is eliminated via covalent bonding between the insoluble short-chain sulfur species and carbon backbone.

Selectivity Map for the Late Stages of CO and CO Reduction to C Species on Copper Electrodes.

The electrochemical CO and CO reduction reactions (CORR and CO RR) using copper catalysts and renewable electricity hold promise as a carbon-neutral route to produce commodity chemicals and fuels. However, the exact mechanisms and structure sensitivity of Cu electrodes toward C products are still under debate. Herein, we investigate ethylene oxide reduction (EOR) as a proxy to the late stages of CORR to ethylene, and the results are compared to those of acetaldehyde reduction to ethanol.

2H-MoS on MoCT MXene Nanohybrid for Efficient and Durable Electrocatalytic Hydrogen Evolution.

The development of highly efficient and durable earth-abundant hydrogen evolution reaction (HER) catalysts is crucial for the extensive implementation of the hydrogen economy. Members of the 2D MXenes family, particularly MoCT, have recently been identified as promising HER catalysts. However, their inherent oxidative instability in air and aqueous electrolyte solutions is hindering their widespread use.

Defect-Enhanced CO Reduction Catalytic Performance in O-Terminated MXenes.

Electrochemical carbon dioxide reduction reaction (CO RR) represents a promising way to generate fuels and chemical feedstock sustainably. Recently, studies have shown that two-dimensional metal carbides and nitrides (MXenes) can be promising CO RR electrocatalysts due to the alternating -C and -H coordination with intermediates that decouples scaling relations seen on transition metal catalysts. However, further by tuning the electronic and surface structure of MXenes it should still be possible to reach higher turnover number and selectivities.

Rational Design of Two-Dimensional Transition Metal Carbide/Nitride (MXene) Hybrids and Nanocomposites for Catalytic Energy Storage and Conversion.

Electro-, photo-, and photoelectrocatalysis play a critical role toward the realization of a sustainable energy economy. They facilitate numerous redox reactions in energy storage and conversion systems, enabling the production of chemical feedstock and clean fuels from abundant resources like water, carbon dioxide, and nitrogen. One major obstacle for their large-scale implementation is the scarcity of cost-effective, durable, and efficient catalysts.

Two-Dimensional Titanium and Molybdenum Carbide MXenes as Electrocatalysts for CO Reduction.

Electrocatalytic CO reduction reaction (CORR) is an attractive way to produce renewable fuel and chemical feedstock, especially when coupled with efficient CO capture and clean energy sources. On the fundamental side, research on improving CORR activity still revolves around late transition metal-based catalysts, which are limited by unfavorable scaling relations despite intense investigation. Here, we report a combined experimental and theoretical investigation into electrocatalytic CORR on Ti- and Mo-based MXene catalysts.

Catalytic Effect on CO Electroreduction by Hydroxyl-Terminated Two-Dimensional MXenes.

Electrocatalysis represents a promising method to generate renewable fuels and chemical feedstock from the carbon dioxide reduction reaction (CORR). However, traditional electrocatalysts based on transition metals are not efficient enough because of the high overpotential and slow turnover. MXenes, a family of two-dimensional metal carbides and nitrides, have been predicted to be effective in catalyzing CORR, but a systematic investigation into their catalytic performance is lacking, especially on hydroxyl (-OH)-terminated MXenes relevant in aqueous reaction conditions.

Self-gating in semiconductor electrocatalysis.

The semiconductor-electrolyte interface dominates the behaviours of semiconductor electrocatalysis, which has been modelled as a Schottky-analogue junction according to classical electron transfer theories. However, this model cannot be used to explain the extremely high carrier accumulations in ultrathin semiconductor catalysis observed in our work. Inspired by the recently developed ion-controlled electronics, we revisit the semiconductor-electrolyte interface and unravel a universal self-gating phenomenon through microcell-based in situ electronic/electrochemical measurements to clarify the electronic-conduction modulation of semiconductors during the electrocatalytic reaction.

On the Role of Sulfur for the Selective Electrochemical Reduction of CO to Formate on CuS Catalysts.

The efficient electroreduction of CO has received significant attention as it is one of the crucial means to develop a closed-loop anthropogenic carbon cycle. Here, we describe the mechanistic workings of an electrochemically deposited CuS catalyst that can reduce CO to formate with a Faradaic efficiency (FE) of 75% and geometric current density ( j) of -9.0 mA/cm at -0.

One-Step Facile Synthesis of Cobalt Phosphides for Hydrogen Evolution Reaction Catalysts in Acidic and Alkaline Medium.

Catalysts for hydrogen evolution reaction are in demand to realize the efficient conversion of hydrogen via water electrolysis. In this work, cobalt phosphides were prepared using a one-step, scalable, and direct gas-solid phosphidation of commercially available cobalt salts. It was found that the effectiveness of the phosphidation reaction was closely related to the state of cobalt precursors at the reaction temperature.

Rational Design of Sulfur-Doped Copper Catalysts for the Selective Electroreduction of Carbon Dioxide to Formate.

The selective electroreduction of CO to formate (or formic acid) is of great interest in the field of renewable-energy utilization. In this work, we designed a sulfur-doped Cu O-derived Cu catalyst and showed that the presence of sulfur can tune the selectivity of Cu significantly from the production of various CO reduction products to almost exclusively formate. Sulfur is doped into the Cu catalysts by dipping the Cu substrates into ammonium polysulfide solutions.

Mechanistic Insights into the Enhanced Activity and Stability of Agglomerated Cu Nanocrystals for the Electrochemical Reduction of Carbon Dioxide to n-Propanol.

The reduction of carbon dioxide (CO2) to n-propanol (CH3CH2CH2OH) using renewable electricity is a potentially sustainable route to the production of this valuable engine fuel. In this study, we report that agglomerates of ∼15 nm sized copper nanocrystals exhibited unprecedented catalytic activity for this electrochemical reaction in aqueous 0.1 M KHCO3.

Photocatalytic reduction of CO2 and protons using water as an electron donor over potassium tantalate nanoflakes.

CO2 photoreduction over KTaO3 photocatalysts in water has been investigated. Both reduction (mainly carbon monoxide and hydrogen) and oxidation products (oxygen) were simultaneously detected in the absence of cocatalysts, sacrificial reagents and electrical bias. KTaO3 (KTO) samples were synthesized by solid-state reaction (SSR-KTO) and solvothermal methods in a hexane-water mixture (Hex-KTO) and pure ethanol (Eth-KTO).

Interfacial charge separation in Cu2O/RuO(x) as a visible light driven CO2 reduction catalyst.

We employ transient absorption spectroscopy to record the absorption spectrum of photogenerated charge carriers in Cu2O. We have found that CO2 reduction in Cu2O is limited by fast electron-hole recombination. The deposition of RuOx nanoparticles on Cu2O results in a twofold increased yield of long-lived electrons, indicating partially reduced electron-hole recombination losses.

Dimensionally and compositionally controlled growth of calcium phosphate nanowires for bone tissue regeneration.

Nanostructured biomaterials with controlled morphology and composition are of high interest for bone tissue regeneration. As resorbable and biocompatible materials for bone tissue engineering, calcium phosphate nanowires and nanoneedles with different aspect ratios and compositions have been first synthesized without the use of any toxic surfactants via an energy efficient microwave assisted process. Correlation between solvent composition, mixing methodology and reagent stoichiometric ratios was investigated with the aim of producing orientated growth and varied biphasic composition, resulting in dimensionally controlled growth of materials containing varying hydroxyapatite (HA)/monetite quantities.