Hierarchical Graphene-Based Material for Over 4.0 Wt % Physisorption Hydrogen Storage Capacity

A hierarchical graphene material composed of micropore (∼0.8 nm), mesopore (∼4 nm), and macropore (>50 nm) and with a specific surface area up to 1305 m² g^–1 is fabricated for physisorption hydrogen storage at atmospheric air pressure, showing a capacity over 4.0 wt %, which is significantly higher than reported graphene materials and all other kinds of carbon materials

Activation Enhancement of Citric Acid Cycle to Promote Bioelectrocatalytic Activity of <i>arcA</i> Knockout <i>Escherichia coli</i> Toward High-Performance Microbial Fuel Cell

The bioelectrocatalysis in microbial fuel cells (MFCs) relies on both electrochemistry and metabolism of microbes. We discovered that under MFC microaerobic condition, an <i>arcA</i> knockout mutant Escherichia coli (arcA^–) shows enhanced activation of the citric acid cycle (TCA cycle) for glycerol oxidation, as indicated by the increased key enzymes’ activity in the TCA cycle. Meanwhile, a diffusive electron mediator (hydroxyl quinone derivative) is excreted by the genetically engineered arcA^–, resulting in a much higher power density than its parental strain toward glycerol oxidation. This work demonstrates that metabolic engineering is a feasible approach to construct efficient bioelectrocatalysts for high-performance MFCs

Functionalization of SnO₂ Photoanode through Mg-Doping and TiO₂‑Coating to Synergically Boost Dye-Sensitized Solar Cell Performance

Mg-doped SnO₂ with an ultrathin TiO₂ coating layer was successfully synthesized through a facile nanoengineering art. Mg-doping and TiO₂-coating constructed functionally multi-interfaced SnO₂ photoanode for blocking charge recombination and enhancing charge transfer in dye-sensitized solar cells (DSC). The designed nanostructure might play a synergistic effect on the reducing recombination and prolonging the lifetime in DSC device. Consequently, a maximum power conversion efficiency of 4.15% was obtained for solar cells fabricated with the SnO₂-based photoelectrode, exhibiting beyond 5-fold improvement in comparison with pure SnO₂ nanomterials photoelectrode DSC (0.85%)

Heteropolyacid-Mediated Self-Assembly of Heteropolyacid-Modified Pristine Graphene Supported Pd Nanoflowers for Superior Catalytic Performance toward Formic Acid Oxidation

The in situ growth of Pd nanoflowers on pristine graphene is achieved using phosphomolybdic acid (HPMo) to mediate self-assembly. The HPMo serves simultaneously as a linker, stabilizer, and structure-directing agent, and the nanoflowers are formed by kinetically controlled growth. When the resulting material, Pd nanoflowers on HPMo-modified graphene (HPMo-G) support, is used to catalyze the formic acid oxidation reaction (FAOR), much higher catalytic activity and durability are found than with HPMo-G supported Pd nanospheres, graphene supported Pd nanoparticles, and commercial Pd/C catalysts. The catalytic activity for Pd nanoflowers on HPMo-G is also among the highest reported for Pd-based catalysts. The superior electrocatalytic performance is attributed to the unique nanoflower shape, a promotion by the HPMo mediator, and the excellent support properties of pristine graphene. The use of HPMo to mediate self-assembly of metals on graphene can be extended to fabricate other hybrid nanostructures promising broad applicability

Hierarchically Porous N‑Doped Carbon Nanotubes/Reduced Graphene Oxide Composite for Promoting Flavin-Based Interfacial Electron Transfer in Microbial Fuel Cells

Interfacial electron transfer between an electroactive biofilm and an electrode is a crucial step for microbial fuel cells (MFCs) and other bio-electrochemical systems. Here, a hierarchically porous nitrogen-doped carbon nanotubes (CNTs)/reduced graphene oxide (rGO) composite with polyaniline as the nitrogen source has been developed for the MFC anode. This composite possesses a nitrogen atom-doped surface for improved flavin redox reaction and a three-dimensional hierarchically porous structure for rich bacterial biofilm growth. The maximum power density achieved with the N-CNTs/rGO anode in S. putrefaciens CN32 MFCs is 1137 mW m^–2, which is 8.9 times compared with that of the carbon cloth anode and also higher than those of N-CNTs (731.17 mW m^–2), N-rGO (442.26 mW m^–2), and the CNTs/rGO (779.9 mW m^–2) composite without nitrogen doping. The greatly improved bio-electrocatalysis could be attributed to the enhanced adsorption of flavins on the N-doped surface and the high density of biofilm adhesion for fast interfacial electron transfer. This work reveals a synergistic effect from pore structure tailoring and surface chemistry designing to boost both the bio- and electrocatalysis in MFCs, which also provide insights for the bioelectrode design in other bio-electrochemical systems

One-Pot Synthesis of Co/CoFe₂O₄ Nanoparticles Supported on N‑Doped Graphene for Efficient Bifunctional Oxygen Electrocatalysis

We herein report a facile strategy to synthesize transition metal/spinel oxide nanoparticles coupled with nitrogen-doped graphene (Co/CoFe₂O₄@N-graphene) as an efficient bifunctional electrocatalyst toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This approach involves a spontaneous solution-polymerization of polydopamine (PDA) film on graphene oxide (GO) sheets in the presence of Fe³⁺ and Co²⁺ to form the Fe/Co-PDA-GO precursor, followed by pyrolysis at 800 °C in argon (Ar) atmosphere. During the calcination process, Co/CoFe₂O₄ nanoparticles are in situ formed via high-temperature solid state reaction and are further entrapped by the PDA-derived N-doped carbon layer. As-prepared Co/CoFe₂O₄@N-graphene exhibits highly efficient catalytic activity and excellent stability for both ORR and OER in alkaline solution. This work reports a facile synthetic approach to develop highly active electrocatalysts while offering great flexibility to tailor their components and morphologies and thus provides a useful route to the design and synthesis of a broad variety of electrocatalysts

Smart Magnetic Interaction Promotes Efficient and Green Production of High-Quality Fe₃O₄@Carbon Nanoactives for Sustainable Aqueous Batteries

Efficient and green production of monodispersed Fe₃O₄@carbon (C) nanoactives for commercial aqueous battery usage still remains a great challenge due to issues related to tedious hybrid fabrication and purification procedures. Herein, we put forward an interesting applicable synthetic strategy via a general polymeric process and simple magnetic purification treatments, enabling low-cost and massive production of high-quality Fe₃O₄@C hybrids. In such core–shell configurations, all Fe₃O₄ nanoparticles are tightly encapsulated in permeable <i>N</i>-doped C nanoreactors, showing notable nanostructured superiorities as feasible anodes for aqueous batteries. When tested, the Fe₃O₄@C nanoactives exhibit outstanding anodic performance comprising pretty high electrochemical activity/capacity, greatly prolonged cyclic lifespan in contrast to bare Fe₃O₄ counterparts, and prominent rate capabilities. The as-assembled Ni/Fe full cells can even deliver a high energy/power density up to ∼135 Wh kg^–1/11.5 kW kg^–1, further demonstrating their good potential in practical applications. Our smart magnetic purification strategy may hold great promise in addressing critical issues of producing high-quality and affordable Fe₃O₄@C hybrids, not only for energy-storage fields but also in other broad ranges covering catalysts and biosensors

Architecture Engineering of Hierarchically Porous Chitosan/Vacuum-Stripped Graphene Scaffold as Bioanode for High Performance Microbial Fuel Cell

The bioanode is the defining feature of microbial fuel cell (MFC) technology and often limits its performance. In the current work, we report the engineering of a novel hierarchically porous architecture as an efficient bioanode, consisting of biocompatible chitosan and vacuum-stripped graphene (CHI/VSG). With the hierarchical pores and unique VSG, an optimized bioanode delivered a remarkable maximum power density of 1530 mW m^–2 in a mediator-less MFC, 78 times higher than a carbon cloth anode

Hydrothermally Treating High-Ti Cinder for a Near Full-Sunlight-Driven Photocatalyst toward Highly Efficient H₂ Evolution

A major drawback of conventional photocatalysts like TiO₂ is the limit of only working under ultraviolet irradiation. As a solution, visible-light-driven photocatalysts have been explored in recent years but full-sunlight-driven photocatalysts are still lacking. Herein, multielement-codoped (Mn, Fe, Si, Al, S, F, etc.) TiO₂ nanomaterials were prepared from an industrial high-Ti cinder (HiTi) by a two-step hydrothermal method using NaOH and NH₄F (or H₂O) as morphology controlling agents. The prepared HiTi photocatalyst exhibits a strong absorption at near full-sunlight spectrum (300–800 nm). Among all TiO₂-based photocatalysts without any noble metal cocatalyst, the photocatalytic H₂ evolution rate on NaOH- and H₂O-hydrothermally treated HiTi (HiTi-TiO₂) is remarkably superior to the reference P25 TiO₂ powders by a factor of 3.8 and thus is the highest. However, NaOH- and NH₄F-treated HiTi (HiTi-TiO₂-F) shows a lower photoreactivity than HiTi-TiO₂ does. Mechanistic studies show that the multielement-doped TiO₂ can synergistically harvest full span sunlight to greatly increase light absorption, while suppressing the charge recombination and reducing the reaction barriers for efficient water splitting. Importantly, the amount of produced industrial cinder is huge in China, and it is dumped on the ground in very large mounds, which results in serious pollution. This study may open a promising recycling approach to treat the waste for sustainable energy use

Integrated Sandwich-Paper 3D Cell Sensing Device to <i>In Situ</i> Wirelessly Monitor H₂O₂ Released from Living Cells

Point-of-care testing (POCT) has attracted great interest because of its prominent advantages of rapidness, precision, portability, and real-time monitoring, thus becoming a powerful biomedical device in early clinical diagnosis and convenient medical treatments. However, its complicated manufacturing process and high expense severely impede mass production and broad applications. Herein, an innovative but inexpensive integrated sandwich-paper three-dimensional (3D) cell sensing device is fabricated to in situ wirelessly detect H2O2 released from living cells. The paper-based electrochemical sensing device was constructed by a sealed sandwiched bottom plastic film/fiber paper/top hole-centered plastic film that was printed with patterned electrodes. A new (Fe, Mn)3(PO4)2/N-doped carbon nanorod was developed and immobilized on the sensing carbon electrode while cell culture solution filled the exposed fiber paper, allowing living cells to grow on the fiber paper surrounding the electrode. Due to the significantly shortening diffusion distance to access the sensing sites by such a unique device and a rationally tuned ratio of Fe2+/Mn2+, the device exhibits a fast response time (0.2 s), a low detection limit (0.4 μM), and a wide detection range (2–3200 μM). This work offers great promise for a low-cost and highly sensitive POCT device for practical clinic diagnosis and broad POCT biomedical applications