Despite the growing demand for hydrogen peroxide it is almost exclusively manufactured by the energy-intensive anthraquinone process. Alternatively, H2O2 can be produced electrochemically via the ...two-electron oxygen reduction reaction, although the performance of the state-of-the-art electrocatalysts is insufficient to meet the demands for industrialization. Interestingly, guided by first-principles calculations, we found that the catalytic properties of the Co–N4 moiety can be tailored by fine-tuning its surrounding atomic configuration to resemble the structure-dependent catalytic properties of metalloenzymes. Using this principle, we designed and synthesized a single-atom electrocatalyst that comprises an optimized Co–N4 moiety incorporated in nitrogen-doped graphene for H2O2 production and exhibits a kinetic current density of 2.8 mA cm−2 (at 0.65 V versus the reversible hydrogen electrode) and a mass activity of 155 A g−1 (at 0.65 V versus the reversible hydrogen electrode) with negligible activity loss over 110 hours.Producing H2O2 electrochemically currently use electrocatalysts that are insufficient to meet the demands for industrialization. A single-atom electrocatalyst with an optimized Co–N4 moiety incorporated in nitrogen-doped graphene is shown to exhibit enhanced performance for H2O2 production.
The reversible and cooperative activation process, which includes electron transfer from surrounding redox mediators, the reversible valence change of cofactors and macroscopic functional/structural ...change, is one of the most important characteristics of biological enzymes, and has frequently been used in the design of homogeneous catalysts. However, there are virtually no reports on industrially important heterogeneous catalysts with these enzyme-like characteristics. Here, we report on the design and synthesis of highly active TiO2 photocatalysts incorporating site-specific single copper atoms (Cu/TiO2) that exhibit a reversible and cooperative photoactivation process. Our atomic-level design and synthetic strategy provide a platform that facilitates valence control of co-catalyst copper atoms, reversible modulation of the macroscopic optoelectronic properties of TiO2 and enhancement of photocatalytic hydrogen generation activity, extending the boundaries of conventional heterogeneous catalysts.Reversible and cooperative activation processes are important characteristics of biological enzymes and can be used in designing catalysts. Highly active TiO2 photocatalysts incorporated with site-specific single copper atoms are now shown to exhibit such a photoactivation process.
Compared to nanostructured platinum (Pt) catalysts, ordered Pt-based intermetallic nanoparticles supported on a carbon substrate exhibit much enhanced catalytic performance, especially in fuel cell ...electrocatalysis. However, direct synthesis of homogeneous intermetallic alloy nanocatalysts on carbonaceous supports with high loading is still challenging. Herein, we report a novel synthetic strategy to directly produce highly dispersed MPt alloy nanoparticles (M = Fe, Co, or Ni) on various carbon supports with high catalyst loading. Importantly, a unique bimetallic compound, composed of M(bpy)32+ cation (bpy = 2,2′-bipyridine) and PtCl62– anion, evenly decomposes on carbon surface and forms uniformly sized intermetallic nanoparticles with a nitrogen-doped carbon protection layer. The excellent oxygen reduction reaction (ORR) activity and stability of the representative reduced graphene oxide (rGO)-supported L10-FePt catalyst (37 wt %-FePt/rGO), exhibiting 18.8 times higher specific activity than commercial Pt/C catalyst without degradation over 20 000 cycles, well demonstrate the effectiveness of our synthetic approach toward uniformly alloyed nanoparticles with high homogeneity.
We use a regular arrangement of kirigami elements to demonstrate an inverse design paradigm for folding a flat surface into complex target configurations. We first present a scheme using arrays of ...disclination defect pairs on the dual to the honeycomb lattice; by arranging these defect pairs properly with respect to each other and choosing an appropriate fold pattern a target stepped surface can be designed. We then present a more general method that specifies a fixed lattice of kirigami cuts to be performed on a flat sheet. This single pluripotent lattice of cuts permits a wide variety of target surfaces to be programmed into the sheet by varying the folding directions.
Significance How can flat surfaces be transformed into useful three-dimensional structures? Recent research on origami techniques has led to algorithmic solutions to the inverse design problem of prescribing a set of folds to form a desired target surface. The fold patterns generated are often very complex and so require a convoluted series of deformations from the flat to the folded state, making it difficult to implement these designs in self-assembling systems. We propose a design paradigm that employs lattice-based kirigami elements, combining the folding of origami with cutting and regluing techniques. We demonstrate that this leads to a pluripotent design in which a single kirigami pattern can be robustly manipulated into a variety of three-dimensional shapes.
Pd is one of the most effective catalysts for the electrochemical reduction of CO2 to formate, a valuable liquid product, at low overpotential. However, the intrinsically high CO affinity of Pd makes ...the surface vulnerable to CO poisoning, resulting in rapid catalyst deactivation during CO2 electroreduction. Herein, we utilize the interaction between metals and metal–organic frameworks to synthesize atomically dispersed Au on tensile-strained Pd nanoparticles showing significantly improved formate production activity, selectivity, and stability with high CO tolerance. We found that the tensile strain stabilizes all reaction intermediates on the Pd surface, whereas the atomically dispersed Au selectively destabilizes CO* without affecting other adsorbates. As a result, the conventional COOH* versus CO* scaling relation is broken, and our catalyst exhibits 26- and 31-fold enhancement in partial current density and mass activity toward electrocatalytic formate production with over 99% faradaic efficiency, compared to Pd/C at −0.25 V versus RHE.
Capacitive deionization (CDI) based on ion electrosorption has recently emerged as a promising desalination technology due to its low energy consumption and environmental friendliness compared to ...conventional purification technologies. Carbon-based materials, including activated carbon (AC), carbon aerogel, carbon cloth, and carbon fiber, have been mostly used in CDI electrodes due their high surface area, electrochemical stability, and abundance. However, the low electrical conductivity and non-regular pore shape and size distribution of carbon-based electrodes limits the maximization of the salt removal performance of a CDI desalination system using such electrodes. Metal-organic frameworks (MOFs) are novel porous materials with periodic three-dimensional structures consisting of metal center and organic ligands. MOFs have received substantial attention due to their high surface area, adjustable pore size, periodical unsaturated pores of metal center, and high thermal and chemical stabilities. In this study, we have synthesized ZIF-67 using CNTs as a substrate to fully utilize the unique advantages of both MOF and nanocarbon materials. Such synthesis of ZIF-67 carbon nanostructures was confirmed by TEM, SEM, and XRD. The results showed that the 3D-connected ZIF-67 nanostructures bridging by CNTs were successfully prepared. We applied this nanostructured ZIF-67@CNT to CDI electrodes for desalination. We found that the salt removal performance was significantly enhanced by 88% for 30% ZIF-67@CNTs-included electrodes as compared with pristine AC electrodes. This increase in salt removal behavior was analyzed by electrochemical analysis such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements, and the results indicate reduced electrical impedance and enhanced electrode capacitance in the presence of ZIF-67@CNTs.
Aqueous paper batteries were fabricated and demonstrated based on LiMn sub(2)O sub(4) and carbon coated TiP sub(2)O sub(7). Carbon nanotubes conformally coated commercial paper, which served as ...current collectors. Anode and cathode slurries penetrated these conductive substrates well. Aqueous paper batteries were tested electrochemically, exhibiting excellent rate capability and reasonable cycling life. TiP sub(2)O sub(7) dissolution accounts for the observed capacity fade.
Conducting polymers (CPs) are by far the most studied organic materials for supercapacitors. Yet, their structural instability stemming from volumetric expansion/contraction during charge/discharge ...results in capacitance loss after moderate cycling that limits their applications. Here, we show that the remarkable cycling stability, capacitance, and rate performance can be achieved by replacing conventional electrode additives (carbon black or insulating polymer binder) with titanium carbide (Ti
3
C
2
T
x
) MXene. Using polyaniline (PANI) as a model system, an addition of only 15 wt% of Ti
3
C
2
T
x
MXene binder delivered remarkable capacitance retention of 96% after 10 000 cycles at 50 mV s
−1
and high-rate capability with a capacitance of 434 F g
−1
. Using density functional theory (DFT) calculations, we show that, unlike insulating polymer binders, surface groups of MXene bond to PANI with a significantly high binding energy (up to −2.11 eV)
via
a charge transfer mechanism. This is one of the key mechanisms to achieve a high electrochemical performance of the CP-based electrodes when MXene is used as a binder. We expect that a similar approach can be used for stabilizing other organic electrode materials.
Unlike conventional additives, the use of MXene as a binder improves the electrochemical performance of conducting polymers. The approach is extendable to a large family of poorly conducting organic materials for sustainable energy storage devices.
Single-atom catalysts are playing a pivotal-role in understanding atomic-level photocatalytic processes. However, single-atoms are typically non-uniformly distributed on photocatalyst surfaces, ...hindering the systematic investigation of structure–property correlation at atomic precision. Herein, by combining material design, spectroscopic analyses, and theoretical studies, we investigate the atomic-level CO2 photoreduction process on TiO2 photocatalysts with uniformly stabilized transition metal single-atoms. First, the electronic interaction between single Cu atoms and the surrounding TiO2 affects the reducibility of the TiO2 surface, leading to spontaneous O vacancy formation near Cu atoms. The coexistence of Cu atoms and O vacancies cooperatively stabilizes CO2 intermediates on the TiO2 surface. Second, our approach allows us to control the spatial distribution of uniform single Cu atoms on TiO2, and demonstrate that neighboring Cu atoms simultaneously engage in the interaction with CO2 intermediates by controlling the charge localization. Optimized Cu1/TiO2 photocatalysts exhibit 66-fold enhancement in CO2 photoreduction performance compared to the pristine TiO2.
Single‐atom nanozymes (SAzymes) are considered promising alternatives to natural enzymes. The catalytic performance of SAzymes featuring homogeneous, well‐defined active structures can be enhanced ...through elucidating structure‐activity relationship and tailoring physicochemical properties. However, manipulating enzymatic properties through structural variation is an underdeveloped approach. Herein, the synthesis of edge‐rich Fe single‐atom nanozymes (FeNC‐edge) via an H2O2‐mediated edge generation is reported. By controlling the number of edge sites, the peroxidase (POD)‐ and oxidase (OXD)‐like performance is significantly enhanced. The activity enhancement results from the presence of abundant edges, which provide new anchoring sites to mononuclear Fe. Experimental results combined with density functional theory (DFT) calculations reveal that FeN4 moieties in the edge sites display high electron density of Fe atoms and open N atoms. Finally, it is demonstrated that FeNC‐edge nanozyme effectively inhibits tumor growth both in vitro and in vivo, suggesting that edge‐tailoring is an efficient strategy for developing artificial enzymes as novel catalytic therapeutics.
Geometric tuning of single‐atom active sites is desirable way to enhance catalytic activity. H2O2‐etching to carbon matrix generates abundant edge‐located FeN4 sites with distinct geometric and electronic structures compared to basal plane‐located FeN4 sites. FeNC‐edge with the unique local environment exhibits remarkably improved multi‐enzymatic activity and inhibits tumor growth effectively.
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