High-Affinity-Assisted Nanoscale Alloys as Remarkable Bifunctional Catalyst for Alcohol Oxidation and Oxygen Reduction Reactions

A key challenge in developing fuel cells is the fabrication of low-cost electrocatalysts with high activity and long durability for the two half-reactions, i.e., the methanol/ethanol oxidation reaction (MOR/EOR) and the oxygen reduction reaction (ORR). Herein, we report a conductivity-enhanced bifunctional electrocatalyst of nanoscale-coated Pt-Pd alloys on both tin-doped indium (TDI) and reduced graphene oxide (rGO), denoted as Pt-Pd@TDI/rGO. The mass activities of Pt in the Pt-Pd@TDI/rGO hybrid toward MOR, EOR, and ORR are 2590, 1500, and 2690 mA/mg, respectively. The ORR Pt specific activity and mass activity of the electrocatalyst are 17 and 28 times larger, respectively, than commercial Pt/C catalysts. All these remarkable catalytic performances are attributed to the role of TDI in enhancing the catalytic activity,by protecting Pt from oxidation as well as rapid mass/charge transfer due to the synergistic effect between surface Pt-Pd alloys and TDI/rGO

Accelerated Bone Regeneration by Two-Photon Photoactivated Carbon Nitride Nanosheets

Human bone marrow-derived mesenchymal stem cells (hBMSCs) present promising opportunities for therapeutic medicine. Carbon derivatives showed only marginal enhancement in stem cell differentiation toward bone formation. Here we report that red-light absorbing carbon nitride (C3N4) sheets lead to remarkable proliferation and osteogenic differentiation by runt-related transcription factor 2 (Runx2) activation, a key transcription factor associated with osteoblast differentiation. Accordingly, highly effective hBMSCs-driven mice bone regeneration under red light is achieved (91% recovery after 4 weeks compared to 36% recovery in the standard control group in phosphate-buffered saline without red light). This fast bone regeneration is attributed to the deep penetration strength of red light into cellular membranes via tissue and the resulting efficient cell stimulation by enhanced photocurrent upon two-photon excitation of C3N4 sheets near cells. Given that the photoinduced charge transfer can increase cytosolic Ca2+ accumulation, this increase would promote nucleotide synthesis and cellular proliferation/differentiation. The cell stimulation enhances hBMSC differentiation toward bone formation, demonstrating the therapeutic potential of near-infrared two-photon absorption of C3N4 sheets in bone regeneration and fracture healing.ope

Design of Large-Scale Rectangular Cells for Rechargeable Seawater Batteries

Rechargeable seawater batteries (SWBs) are regarded as sustainable alternatives to Li-ion batteries due to the use of an unlimited and free source of Na ion active materials. Although many approaches including the introduction of new catalysts have successfully improved the performance of SWBs, reconsidering the cell design is an urgent requirement to improve the performance and scale up the production of practical batteries. In this study, by adjusting the maximum space efficiency, a rectangular cell is developed which due to its unique architecture, benefits from optimized contact to improve the overall charge transfer in the system. In view of the rigidity of the solid electrolyte, the novel cell model is intended to have adequate flexibility to be easily transported and practically utilized. Furthermore, the enhanced efficiency of the parallel stacked modules, indicates the capability of this cell in practical use. The designed catalyst-free cell system shows a record capacity of 3.8 Ah (47.5 Ah kg(-1)), energy of 11 Wh (137.5 Wh kg(-1)), and peak power of 523 mW for individual unit cell, while it also retains performance up to 100 cycles. This design paves the way for commercializing rechargeable seawater batteries

Disinfection-Dechlorination Battery for Safe Water Production

With increasing population growth, it is necessary to meet safe water demands. Water disinfection through chlorination is the most commonly used method for safe water production. The electrolysis of salted water is a promising technology for the on-site generation of disinfecting agents, however, its low efficiency and inability to neutralize the remaining free chlorine makes electrolysis inefficient. The introduction of a cation permeable membrane between anode and cathode can help to improve the disinfection efficiency and also dechlorinate the remained free chlorine by switching the anode and cathode. However, the scale formation on the membrane will reduce the performance of the system. In this study, with using a Na-selective membrane for separating anode and cathode, we propose a disinfection-dechlorination battery (DD-battery) consisting of an anode for energy storage through Na+ reduction to metal Na and a cathode for disinfection via Cl??? oxidation to free chlorine species. The stored energy in the anode is released during discharge, and the system can dechlorinate the remaining free chlorine to prevent disinfectant toxicity. This self-disinfection-dechlorination during battery cycling can be combined with renewable energy sources for efficient water disinfection in remote regions

Graphene-nanoplatelets-supported NiFe-MOF: high-efficiency and ultra-stable oxygen electrodes for sustained alkaline anion exchange membrane water electrolysis

Practical hydrogen production using high-efficiency, low-cost, and stable oxygen electrodes is crucial for a sustainable clean energy future. Herein we report a graphene-nanoplatelets-supported (Ni,Fe) metal-organic framework (MOF) as a superior and ultra-durable (>1000 h) anode for alkaline water electrolysis. The MOF on carbon-fiber paper electrodes requires an overpotential eta = 220 mV to achieve a current density j = 10 mA cm(-2) (eta = 180 mV on nickel foam for j = 20 mA cm(-2)) with a Tafel slope of 51 mV per decade, high turnover frequency (1.22 s(-1)), high faradaic efficiency (99.1%), and long-term durability of 41000 h in continuous electrolysis. In an alkaline anion exchange membrane water electrolyzer (AAEMWE), it exhibits a record current density of 540 mA cm(-2) at 1.85 V at 70 degrees C, outperforming the state-of-the-art Pt/C//IrO2. A breakthrough strategy introduced in membrane electrode assembly fabrication by extending the electrical contact with an aqueous electrolyte offers an additional OH- transport pathway to regenerate the original conductivity of the AAEMWE in continuous electrolysis, without any significant change in the pH of the electrolyte. These findings open up durable, high-performance AAEMWE and direct solar-to-fuel conversion, especially to replace high-cost proton exchange membrane water electrolysis that already works with ultra-pure water

Nickel-Based Electrocatalysts for Energy-Related Applications: Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions

The persistently increasing energy consumption and the low abundance of conventional fuels have raised serious concerns all over the world. Thus, the development of technology for clean-energy production has become the major research priority worldwide. The globalization of advanced energy conversion technologies like rechargeable metal-air batteries, regenerated fuel cells, and water-splitting devices has been majorly benefitted by the development of apposite catalytic materials that can proficiently carry out the pertinent electrochemical processes like oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and water hydrolysis. Despite a handful of superbly performing commercial catalysts, the high cost and low electrochemical stability of precursors have consistently discouraged their long-term viability. As a promising substitute of conventional platinum-, palladium-, iridium-, gold-, silver-, and ruthenium-based catalysts, various transition-metal (TM) ions (for example, Fe, Co, Mo, Ni, V, Cu, etc.) have been exploited to develop advanced electroactive materials to outperform the state-of-the-art catalytic properties. Among these TMs, nickel has emerged as one of the most hopeful constituents due to its exciting electronic properties and anticipated synergistic effect to dramatically alter surface properties of materials to favor electrocatalysis. This review article will broadly confer about recent reports on nickel-based nanoarchitectured materials and their applications toward ORR, OER, HER, and whole water splitting. On the basis of these applications and properties of nickel derivatives, a futuristic outlook of these materials has also been presented

Efficient CO Oxidation by 50-Facet Cu2O Nanocrystals Coated with CuO Nanoparticles

As carbon monoxide oxidation is widely used for various chemical processes (such as methanol synthesis and water-gas shift reactions H2O + CO reversible arrow CO2 + H-2) as well as in industry, it is essential to develop highly energy efficient, inexpensive; and eco-friendly catalysts for CO oxidation. Here we report green synthesis of similar to 10 nm sized CuO nanoparticles (NPs) aggregated on similar to 400 nm sized 50-facet Cu2O polyhedral nanocrystals. This CuO-NPs/50-facet Cu2O shows remarkable CO oxidation reactivity with very high specific CO oxidation activity (4.5 mu mol(CO) m(-2) s(-1) at 130 degrees C) and near-complete 99.5% CO conversion efficiency at similar to 175 degrees C. This outstanding catalytic performance by CuO NPs over the pristine multifaceted Cu2O nanocrystals is attributed to the surface oxygen defects present in CuO NPs which facilitate binding of CO and O-2 on their surfaces. This new material opens up new possibilities of replacing the usage of expensive CO oxidation materials.clos

Intramolecular deformation of zeotype-borogermanate toward a three-dimensional porous germanium anode for high-rate lithium storage

We demonstrate a new class of synthetic process for three-dimensional porous Ge materials (3D-pGe). Starting from zeotype-borogermanate microcubes, the 3D-pGe sample was synthesized through a thermal deformation of artificial Ge-rich zeolite, etching, and subsequent hydrogen reduction. After the synthesis, the resultant byproducts were simply removed by warm water instead of a harmful etchant such as hydrofluoric acid. Benefiting from the structural advantages with meso/macro porosity in the overall framework, the as-prepared 3D-pGe exhibits good electrochemical properties as anode materials for lithium-ion batteries with a high capacity (770 mA h g(-1)), cycling stability (capacity retention over 83%) after 250 cycles at 1C, and excellent rate capability (32% for 10C with respect to C/5) as well as pseudocapacitive contribution by surface-controlled reaction. This study paves the way to a new synthesis strategy of 3D porous Ge anode materials from zeolite for large-scale energy storage application

Ruthenium Core-Shell Engineering with Nickel Single Atoms for Selective Oxygen Evolution via Nondestructive Mechanism

To develop effective electrocatalytic splitting of acidic water, which is a key reaction for renewable energy conversion, the fundamental understanding of sluggish/destructive mechanism of the oxygen evolution reaction (OER) is essential. Through investigating atom/proton/electron transfers in the OER, the distinctive acid-base (AB) and direct-coupling (DC) lattice oxygen mechanisms (LOMs) and adsorbates evolution mechanism (AEM) are elucidated, depending on the surface-defect engineering condition. The designed catalysts are composed of a compressed metallic Ru-core and oxidized Ru-shell with Ni single atoms (SAs). The catalyst synthesized with hot acid treatment selectively follows AB-LOM, exhibiting simultaneously enhanced activity and stability. It produces a current density of 10/100 mA cm(-2) at a low overpotential of 184/229 mV and sustains water oxidation at a high current density of up to 20 mA cm(-2) over approximate to 200 h in strongly acidic media

Efficient CO Oxidation by 50-Facet Cu₂O Nanocrystals Coated with CuO Nanoparticles

As carbon monoxide oxidation is widely used for various chemical processes (such as methanol synthesis and water-gas shift reactions H₂O + CO ⇄ CO₂ + H₂) as well as in industry, it is essential to develop highly energy efficient, inexpensive, and eco-friendly catalysts for CO oxidation. Here we report green synthesis of ∼10 nm sized CuO nanoparticles (NPs) aggregated on ∼400 nm sized 50-facet Cu₂O polyhedral nanocrystals. This CuO-NPs/50-facet Cu₂O shows remarkable CO oxidation reactivity with very high specific CO oxidation activity (4.5 μmol_CO m^–2 s^–1 at 130 °C) and near-complete 99.5% CO conversion efficiency at ∼175 °C. This outstanding catalytic performance by CuO NPs over the pristine multifaceted Cu₂O nanocrystals is attributed to the surface oxygen defects present in CuO NPs which facilitate binding of CO and O₂ on their surfaces. This new material opens up new possibilities of replacing the usage of expensive CO oxidation materials