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Powerful, flexible, and small energy storage devices are becoming increasingly important. As a typical two-dimensional titanium carbide, the Ti3C2Tx MXene film has been widely used as an electrode material for flexible energy storage devices due to its ultra-high electrical conductivity, superior capacitance, and excellent mechanical flexibility. In this work, we incorporate mesoporous gold nanoparticles (Au NPs) with abundant interior void spaces into flexible Ti3C2Tx MXene films to enhance conductivity, provide more electroactive sites, and shorten ion diffusion paths. The MXene composite film with 5 wt% mesoporous Au NPs (M/A-0.05) has gravimetric capacitances up to 332 F g−1 at a current density of 1 A g−1, representing a 59% increase over the pure MXene film. Flexible symmetric solid-state micro-supercapacitors (MSCs) in PVA/H2SO4 electrolyte are fabricated with this MXene composite film, which shows a wider voltage window (0–1.2 V) compared to aqueous symmetric supercapacitors in 3 M H2SO4 electrolyte (0–0.6 V). The MSCs have a large surface area, enabling the MXene composite film with mesoporous Au NPs to be efficiently excited with light. Electromagnetic (EM) simulations performed on mesoporous Au NPs in a high refractive index material like Ti3C2 MXene show that light can excite broadband multipolar plasmon resonances that should contribute indirectly to photocurrent by generating heat in the interstitial space between MXene flakes. Thus, the photo-illuminated MSC device based on M/A-0.05 generates ∼2X photocurrent response compared to the MSC device based on the pure MXene film and has a capacitance 6.2% higher than under dark conditions. This work explains how mesoporous Au NPs can augment and improve the properties of MXene-based composite film electrodes that are capable of both harvesting and storing energy for photo-enhanced supercapacitors. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are promising high‐performance capacitive deionization (CDI) materials. Strategies to optimize CDI performance of COFs focus largely on hybridization with conductive substrates, to improve their their intrinsically poor conductivity. A new structure‐function relationship between COFs and their substrates is proposed here based on substrate‐induced surface curvature. Graphene (zero‐curvature) and carbon nanotubes (CNT, curved) are selected as COF growthsubstrates to assess the effect of curvature engineering effect on CDI performance of TpPa‐SO3H‐COF. Ultrahigh ion (Na+) adsorption capacity (58.74 mg g−1) is achieved by CNT‐COF hybrid (cf. compared to graphene‐COF hybrid 34.20 mg g−1), demonstrating the significance of curvature engineering. Notably, the corresponding salt (NaCl) adsorption capacity of CNT‐COF hybrid reaches 149.25 mg g−1 in 1000 ppm at 1.2 V, representing state‐of‐the‐art CDI performance, and the highest value among organic CDI electrodes. X‐ray photoelectron spectroscopy and theoretical calculations subsequently reveal that substrate curvature can induce local strain, which regulates charge distribution within the COF skeleton, causing a lower binding energy state for Na+ adsorption. Electrochemical quartz crystal microbalance measurements revealed faster Na+ adsorption kinetics of CNT‐COF due to regulated charge distribution within COF skeleton induced by substrate curvature. This work gives new insight into design of COF materials based on curvature engineering. [ABSTRACT FROM AUTHOR]

High Entropy Alloys (HEAs) are a versatile material with unique properties, tailored for various applications. They enable pH‐sensitive electrocatalytic transformations like hydrogen evolution reaction (HER) and hydrogen oxidation reactions (HOR) in alkaline media. Mesoporous nanostructures with high surface area are preferred for these electrochemical reactions, but designing mesoporous HEA sis challenging. To overcome this challenge, a low‐temperature triblock copolymer‐assisted wet‐chemical approach is developed to produce mesoporous HEA nanospheres composed of PtPdRuMoNi systems with sufficient entropic mixing. Owing to active sites with inherent entropic effect, mesoporous features, and increased accessibility, optimized HEA nanospheres promote strong HER/HOR performance in alkaline medium. At 30 mV nominal overpotential, it exhibits a mass activity of ≈167 (HER) and 151 A gPt−1 (HOR), far exceeding commercial Pt‐C electrocatalysts (34 and 48 A gPt−1) and many recently reported various alloys. The Mott‐Schottky analysis reveals HEA nanospheres inherit high charge carrier density, positive flat band potential, and smaller charge transfer barrier, resulting in better activity and faster kinetics. This micelle‐assisted synthetic enable the exploration of the compositional and configurational spaces of HEAs at relatively low temperature, while simultaneously facilitating the introduction of mesoporous nanostructures for a wide range of catalytic applications. [ABSTRACT FROM AUTHOR]

We report an efficient ORR electrocatalyst containing cobalt single atom and cobalt nanoparticle active sites embedded in a porous nitrogen-doped graphitic carbon network. The robust electrocatalyst exhibits superior electrochemical ORR activity with onset and half-wave potentials of 0.96 V and 0.87 V (vs. reversible hydrogen electrode), respectively, and has excellent durability and methanol tolerance further enhancing the potential of this system for practical applications. [ABSTRACT FROM AUTHOR]

The photoreduction of carbon dioxide (CO2) into renewable synthetic fuels is an attractive approach for generating alternative energy feedstocks that may compete with and eventually displace fossil fuels. However, it is challenging to accurately trace the products of CO2 photoreduction on account of the poor conversion efficiency of these reactions and the imperceptible introduced carbon contamination. Isotope-tracing experiments have been used to solve this problem, but they frequently yield false-positive results because of improper experimental execution and, in some cases, insufficient rigor. Thus, it is imperative that accurate and effective strategies for evaluating various potential products of CO2 photoreduction are developed for the field. Herein, we experimentally demonstrate that the contemporary approach toward isotope-tracing experiments in CO2 photoreduction is not necessarily rigorous. Several examples of where pitfalls and misunderstandings arise, consequently making isotope product traceability difficult, are demonstrated. Further, we develop and describe standard guidelines for isotope-tracing experiments in CO2 photoreduction reactions and then verify the procedure using some reported photoreduction systems. Current verification of CO2 photoreduction products using isotope-tracer methods is insufficient and can provide false-positive results. Here, rigorous protocols and case studies are presented to avoid pitfalls in isotope-tracer experiments. [ABSTRACT FROM AUTHOR]