Search

A novel hybrid electrocatalyst consisting of nitrogen-doped graphene/cobalt-embedded porous carbon polyhedron (N/Co-doped PCP//NRGO) is prepared through simple pyrolysis of graphene oxide-supported cobalt-based zeolitic imidazolate-frameworks. Remarkable features of the porous carbon structure, N/Co-doping effect, introduction of NRGO, and good contact between N/Co-doped PCP and NRGO result in a high catalytic efficiency. The hybrid shows excellent electrocatalytic activities and kinetics for oxygen reduction reaction in basic media, which compares favorably with those of the Pt/C catalyst, together with superior durability, a four-electron pathway, and excellent methanol tolerance. The hybrid also exhibits superior performance for hydrogen evolution reaction, offering a low onset overpotential of 58 mV and a stable current density of 10 mA cm−2 at 229 mV in acid media, as well as good catalytic performance for oxygen evolution reaction (a small overpotential of 1.66 V for 10 mA cm−2 current density). The dual-active-site mechanism originating from synergic effects between N/Co-doped PCP and NRGO is responsible for the excellent performance of the hybrid. This development offers an attractive catalyst material for large-scale fuel cells and water splitting technologies. [ABSTRACT FROM AUTHOR]

Abstract: Hollow carbonaceous composites (HCCs) possessing sphere and hemisphere shape, which had wide size distribution between several tens of nanometers and several micrometers, were prepared through a facile hydrothermal method using glucose as carbon source with the assistance of sodium dodecyl sulfate (SDS). Pyrolysis of these hollow carbonaceous composites at 900°C under nitrogen flow produced carbonized hollow carbon spheres (HCSs) without changing their structures. Platinum (Pt) was directly deposited on the surface of the HCSs by incipient wet method, using the NaBH4 as the reductant. TEM, SEM, powder XRD and FT-IR were utilized to characterize all these samples. It was found that Pt nanoparticles were uniformly anchored on the outer and the inner surface of HCSs. The electrocatalytic properties of the Pt/HCS electrode for methanol oxidation have been investigated through cyclic voltammetry and chronoamperometry. The Pt/HCS electrode showed significantly higher electrocatalytic activity and more stability for methanol oxidation compared with Pt supported carbon microspheres (Pt/CMs) and commercial carbon (Pt/XC-72) electrode. The excellent performance for the Pt/HCS might be attributed to the high dispersion of platinum catalysts and the particular hollow structure of HCSs. [Copyright &y& Elsevier]

Aqueous electrochemical devices such as batteries and electrolytic cells have emerged as promising energy storage and conversion systems owing to their environmental friendliness, low cost, and high safety characteristics. However, grand challenges are faced to address some critical issues, including how to enhance the potential window and energy density of electrochemical power devices (e.g. fuel cells, batteries, and supercapacitors), and how to minimize the energy consumption in electrolysis. The use of decoupled acid–base asymmetric electrolytes shows great potential in improving the performance of aqueous devices by electrochemically converting the conventional thermal energy of acid–base neutralization into electricity, i.e., electrochemical neutralization energy (ENE). This review aims to introduce the little-known concept of the ENE, including its development history, thermodynamic fundamentals, operating principles, device configurations, and applications. The recent progress made in ENE-assisted electrochemical energy devices emphasizing fuel cells, batteries, supercapacitors, and electrolytic cells is summarized specifically. Finally, the challenges and future perspectives of ENE associated technology are discussed. It is believed that this tutorial review will give a better understanding of the mechanism and operating principles of the ENE to newcomers, which would shed light on the innovative design and fabrication of ENE-assisted devices and thus pave the way for the development of high-performance aqueous electrochemical energy devices. [ABSTRACT FROM AUTHOR]

Sodium borohydride (NaBH4) has earned recognition as a promising hydrogen carrier, attributed to its exceptional hydrogen storage capacity, boasting a high theoretical storage capacity of 10.8 wt %. Nonetheless, the utilization of traditional pyrolysis and hydrolysis methods still presents a formidable challenge in achieving controlled hydrogen generation especially under ambient conditions. In this work, we report an innovative electrochemical strategy for production H2 by coupling NaBH4 electrooxidation reaction (BOR) at anode in alkaline media with hydrogen evolution reaction (HER) at cathode in acidic media. To implement this, we have developed a bifunctional electrocatalyst denoted as Pd‐Mo2C@CNTs, wherein Pd nanoparticles are grown in situ on Mo2C embedded within N‐doped carbon nanotubes. This electrocatalyst demonstrates exceptional performance in catalyzing both alkaline BOR and acidic HER. We have developed a hybrid acid/alkali cell, utilizing Pd/Mo2C@CNTs as the anode and cathode electrocatalysts. This configuration showcases remarkable capabilities for self‐sustained, precise, and uninterrupted indirect release of H2 stored in NaBH4, even at high current densities of 100 mA cm−2 with a Faraday efficiency approaching 100 %. Additionally, this electrochemical device exhibits significant promise as a fuel cell, with the ability to deliver a maximum power density of 20 mW cm−2. [ABSTRACT FROM AUTHOR]

Sodium borohydride (NaBH4) has earned recognition as a promising hydrogen carrier, attributed to its exceptional hydrogen storage capacity, boasting a high theoretical storage capacity of 10.8 wt %. Nonetheless, the utilization of traditional pyrolysis and hydrolysis methods still presents a formidable challenge in achieving controlled hydrogen generation especially under ambient conditions. In this work, we report an innovative electrochemical strategy for production H2 by coupling NaBH4 electrooxidation reaction (BOR) at anode in alkaline media with hydrogen evolution reaction (HER) at cathode in acidic media. To implement this, we have developed a bifunctional electrocatalyst denoted as Pd‐Mo2C@CNTs, wherein Pd nanoparticles are grown in situ on Mo2C embedded within N‐doped carbon nanotubes. This electrocatalyst demonstrates exceptional performance in catalyzing both alkaline BOR and acidic HER. We have developed a hybrid acid/alkali cell, utilizing Pd/Mo2C@CNTs as the anode and cathode electrocatalysts. This configuration showcases remarkable capabilities for self‐sustained, precise, and uninterrupted indirect release of H2 stored in NaBH4, even at high current densities of 100 mA cm−2 with a Faraday efficiency approaching 100 %. Additionally, this electrochemical device exhibits significant promise as a fuel cell, with the ability to deliver a maximum power density of 20 mW cm−2. [ABSTRACT FROM AUTHOR]

Transition metal single atoms anchored on nitrogen‐doped carbon (M‐N‐C) matrix with M‐N‐C active sites have shown to be promising catalysts for both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, a hybrid catalyst with low‐level loading of atomic Pt and Co species encapsulated in nitrogen‐doped graphene (Pt@CoN4‐G) is developed. The Pt@CoN4‐G shows low overpotential for HER in wide‐pH electrolyte and manifests improved mass activity with almost eight times greater than that of Pt/C at an overpotential of 50 mV. The Pt@CoN4‐G also exhibits a top‐level ORR activity (half‐wave potential, E1/2 = 0.893 V) and robust stability (>200 h) in alkaline medium. Using theoretical calculations and comprehensive characterizations , the strong metal–support interactions between Pt species and CoN4‐G support and synergistical cooperation of multiple active sites are clarified. A flow alkali‐Al/acid hybrid fuel cell using Pt@CoN4‐G as cathode catalyst delivers a large power density of 222 mW cm−2 with excellent stability to achieve simultaneously hydrogen evolution and electricity generation. In addition, Pt@CoN4‐G endows a flow Zn‐air battery with high power density (316 mW cm−2), good stability under large current density (>100 h at 100 mA cm−2), and long cycle life (over 600 h at 5 mA cm−2). [ABSTRACT FROM AUTHOR]

On page 872 novel nitrogen‐doped graphene/cobalt‐embedded porous carbon polyhedron hybrid electrocatalyst is obtained by Z. H. Wen, J. H. Chen, and co‐workers through a simple strategy. Benefitting from well defined structural features including excellent porous carbon structure, N/Co‐doping effect, introduction of NRGO, and good contact between N/Co‐doped PCP and NRGO sheets, the hybrid exhibits excellent tri‐functional catalytic activities for ORR, HER, and OER with long‐term stability in both acid and basic media. [ABSTRACT FROM AUTHOR]

Cost-effective catalysts are of key importance to the successful deployment of microbial fuel cells (MFCs) for electricity generation from organic wastes. Herein, a novel catalyst prepared by one-step synthesis strategy is reported. The catalyst features N-doped bamboo-like carbon nanotube (BCNT) in which CoNi-alloy is encapsulated at the end and/or the middle section of the tube with many graphene layers inside inner cavities of BCNT (N-G@CoNi/BCNT). The prepared N-G@CoNi/BCNT exhibits a high oxygen reduction reaction (ORR) activity with an early onset potential of 0.06 V vs. Ag/AgCl and a comparable exchange current density to that of commercial Pt/C. The excellent catalytic activity is further evidenced by a high electron transfer number of 3.63. When being applied in MFCs, the N-G@CoNi/BCNT yields an average current density of 6.7 A m −2 , slightly lower than that of Pt/C but with a less mass transfer potential loss. The cost of the N-G@CoNi/BCNT for constructing a 1-m 2 cathode electrode is 200 times lower than that of Pt/C. With such a competitive price and excellent electrocatalytic-activity resulting from its unique morphology, CoNi-alloy/nitrogen dopants, considerable specific surface area, and carbon-coated alloy/graphene hybridization, the present catalyst is a promising candidate for ORR catalysts in MFCs for energy recovery from wastes. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) has been utilized as a versatile feedstock or promising energy carrier in a variety of fields, yet the implementation of high‐rate H2 production presents a grand challenge for its readily accessible application. Herein, a newly alkali‐Al/acid hybrid fuel cell (3AHFC) that shows the capability of rapidly producing H2 upon delivering a considerably high energy density is reported, which is set up by paring Al anode in alkaline anolyte with acidic catholyte and a relatively cheap nanohybrid of Ru nanoparticle decorating crumpled reduced graphene oxide (Ru/c‐rGO) as cathode catalysts. It is demonstrated that the 3AHFC can release a power density of up to 240.6 mW cm−2 with a Faradic efficiency of approaching 99% for fast H2 generation (300 mA cm−2). Such hybrid electrolyte H2‐generation fuel cell can also be extended for either seawater anolyte or metallic Mg anode, presenting great promise for the practice feasibility of on‐site H2 production for applications in tough or even extreme environments. [ABSTRACT FROM AUTHOR]

In an article published in Advanced Functional Materials, researchers Zhenhai Wen, Cheng‐Yan Xu, and their team introduce a low-cost and durable catalyst called Pt@CoN4‐G. This catalyst contains atomic Co and Pt species encapsulated in nitrogen-doped graphene and demonstrates excellent performance in both the hydrogen evolution reaction and the oxygen reduction reaction. The catalyst shows promise for use in flow alkali‐Al/acid hybrid fuel cells and Zn–air batteries. The researchers attribute the catalyst's success to the strong metal support interactions between the Pt species and the CoN4‐G support, as well as the synergistic cooperation of multiple active sites. [Extracted from the article]

Developing high-active, good-stable, and cost-effective electrocatalyst for oxygen reduction reaction (ORR) in all-pH medium is highly desired for the application of various fuel cell systems. Here, a network architecture hybrid with porous nitrogen-doped graphene encapsulated β-FeOOH nanoparticals (β-FeOOH/PNGNs) as ORR electrocatalyst, which exhibits remarkable enhancement ORR performance in terms of activity and stability in pHuniversal medium is reported. Systematic characterization combining with X-ray absorption fine structure analysis and the first principles simulations reveal that the as-formed surface FeO6 active sites that induced by a mass of Fe vacancies in β-FeOOH/PNGNs can significantly lower the thermodynamic barrier of the total reaction, and hence contribute to a remarkable enhancement in ORR activity. [ABSTRACT FROM AUTHOR]

Abstract: An alkaline–acid Zn–H2O fuel cell is proposed for the simultaneous generation of electricity with an open circuit voltage of about 1.25 V and production of H2 with almost 100 % Faradic efficiency. We demonstrate that, as a result of harvesting energy from both electrochemical neutralization and electrochemical Zn oxidation, the as‐developed hybrid cell can deliver a power density of up to 80 mW cm−2 and an energy density of 934 Wh kg−1 and maintain long‐term stability for H2 production with an output voltage of 1.16 V at a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Abstract: An alkaline–acid Zn–H2O fuel cell is proposed for the simultaneous generation of electricity with an open circuit voltage of about 1.25 V and production of H2 with almost 100 % Faradic efficiency. We demonstrate that, as a result of harvesting energy from both electrochemical neutralization and electrochemical Zn oxidation, the as‐developed hybrid cell can deliver a power density of up to 80 mW cm−2 and an energy density of 934 Wh kg−1 and maintain long‐term stability for H2 production with an output voltage of 1.16 V at a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Cobalt oxide hollow nanododecahedra (Co 3 O 4 -HND) is synthesized by a facile thermal transformation of cobalt-based metal-organic framework (Co-MOF, ZIF-67) template. The morphology and properties of the Co 3 O 4 -HND are characterized by a set of techniques, including transmission electron microscope (TEM), powder X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunner–Emmet–Teller (BET). When tested as a non-enzymatic electrocatalyst for glucose oxidation reaction, the Co 3 O 4 -HND exhibits a high activity and shows an outstanding performance for determining glucose with a wide window of 2.0 μM to 6.06 mM, a high sensitivity of 708.4 μA mM −1 cm −2 , a low detection limit of 0.58 μM ( S / N =3), and fast response time(<2 s). Based on the nonenzymatic oxidation of glucose, Co 3 O 4 -HND could be served as an attractive non-enzyme and noble-metal-free electrocatalyst in glucose fuel cell (GFC) due to its excellent electrochemical properties, low cost and facile preparation. [ABSTRACT FROM AUTHOR]

It is of great significance in exploring alternative catalysts to platinum (Pt)-based materials for oxygen reduction reaction (ORR), because this reaction is invariably involved in various fuel cells and metal-air batteries. We herein reported the nitrogen doped graphene nanosheets (NGNSs) with pore volume of as high as 3.42 m/g and investigated their potential application as ORR catalysts, it was demonstrated the NGNSs featured high activity, improved kinetics and excellent long-term stability for ORR. The NGNSs were successfully used as cathode catalysts of microbial fuel cells (MFCs) and performed even better than the commercial Pt/C (Pt 10%) catalysts at the maximum power output. [ABSTRACT FROM AUTHOR]

• Ni@NiO-Cu@CuO/NCS is prepared from MOF material via direct calcination process. • Material favors to human urine urea oxidation and groundwater NO 3 − reduction. • Presence of M2+/M3+ redox couple offers better bifunctional catalytic activity. • Substitution of ORR with NRR launches a new branch of fuel cell named UNFC. Though direct urea fuel cells (DUFCs) show promising potential for green energy generation, the practical feasibility of its on-site installation is yet encumbered by the sluggish electrokinetics and low-value product (H 2 O) of oxygen reduction reaction (ORR). We here report the design and synthesis of a bifunctional hybrid electrocatalyst of nitrogen-doped carbon sheets supporting Ni@NiO-Cu@CuO composites (Ni@NiO-Cu@CuO/NCS) via direct calcination of Ni- and Cu-containing metal organic frameworks (MOFs). The as-derived nanohybrid shows impressively high catalytic performance towards urea oxidation reaction (UOR) in alkali and nitrate reduction reaction (NRR) in acidic electrolyte, which inspire us to set up a urea-nitrate fuel cell (UNFC). Owing to the excellent electrochemical characteristics behaviour of prepared nanostructures, the fabricated UNFC simultaneously exhibits improved fuel cell performance of 22.55 ± 2.3 mW cm−2 and degrade the urine and nitrate at the anode and cathode, respectively. The presented innovative electrochemical device may open up a prime step for the development of renewable UNFC for simultaneous green energy generation and N-containing waste removal. [ABSTRACT FROM AUTHOR]