Carbon-based single-atom catalysts (SACs) are considered to be a perfect platform for studying the structure-activity relationship of different reactions due to the adjustability of their ...coordination environment. Multi-heteroatom doping has been demonstrated as an effective strategy for tuning the coordination environment of carbon-based SACs and enhancing catalytic performance in electrochemical reactions. Herein, recently developed strategies for multi-heteroatom doping, focusing on the regulation of single-atom active sites by heteroatoms in different coordination shells, are summarized. In addition, the correlation between the coordination environment and the catalytic activity of carbon-based SACs are investigated through representative experiments and theoretical calculations for various electrochemical reactions. Finally, concerning certain shortcomings of the current strategies of doping multi-heteroatoms, some suggestions are put forward to promote the development of carbon-based SACs in the field of electrocatalysis.
Novel layered 2D frameworks (C3N and C2N‐450) with well‐defined crystal structures are explored for use as anode materials in lithium‐ion batteries (LIBs) for the first time. As anode materials for ...LIBs, C3N and C2N‐450 exhibit unusual electrochemical characteristics. For example, C2N‐450 (and C3N) display high reversible capacities of 933.2 (383.3) and 40.1 (179.5) mAh g−1 at 0.1 and 10 C, respectively. Furthermore, C3N shows a low hypothetical voltage (≈0.15 V), efficient operating voltage window with ≈85% of full discharge capacity secured at >0.45 V, and excellent cycling stability for more than 500 cycles. The excellent electrochemical performance (especially of C3N) can be attributed to their inherent 2D polyaniline frameworks, which provide large net positive charge densities, excellent structural stability, and enhanced electronic/ionic conductivity. Stable solid state interface films also form on the surfaces of the 2D materials during the charge/discharge process. These 2D materials with promising electrochemical performance should provide insights to guide the design and development of their analogues for future energy applications.
Layered 2D organic frameworks, C3N and C2N‐450, are evaluated as anode materials in lithium‐ion batteries for the first time, showing unusual electrochemical characteristics. New 2D structures should provide insights to guide the design and development of their analogues for future energy applications.
Noble metal (Pt, Ru, and Ir)-based electrocatalysts are currently considered the most active materials for the hydrogen evolution reaction (HER). Although they have been associated with high cost, ...easy agglomeration, and poor stability during the HER reaction, recent efforts to intentionally tailor noble-metal-based catalysts have led to promising improvements, with lower cost and superior activity, which are critical to achieving large-scale production of pure hydrogen. In this mini-review, we focus on the recent advances in noble-metal-based HER electrocatalysts. In particular, the synthesis strategies to enhance cost-effectiveness and the catalytic activity for HER are highlighted.
Developing efficient and stable electrocatalysts is crucial for the electrochemical production of pure and clean hydrogen. For practical applications, an economical and facile method of producing ...catalysts for the hydrogen evolution reaction (HER) is essential. Here, we report ruthenium (Ru) nanoparticles uniformly deposited on multi-walled carbon nanotubes (MWCNTs) as an efficient HER catalyst. The catalyst exhibits the small overpotentials of 13 and 17 mV at a current density of 10 mA cm
in 0.5 M aq. H
SO
and 1.0 M aq. KOH, respectively, surpassing the commercial Pt/C (16 mV and 33 mV). Moreover, the catalyst has excellent stability in both media, showing almost "zeroloss" during cycling. In a real device, the catalyst produces 15.4% more hydrogen per power consumed, and shows a higher Faradaic efficiency (92.28%) than the benchmark Pt/C (85.97%). Density functional theory calculations suggest that Ru-C bonding is the most plausible active site for the HER.
Producing hydrogen using anion exchange membrane (AEM) water electrolysis is a promising approach to address the severe energy crisis facing human society. AEM electrolysis can be integrated with ...intermittent and sustainable energy sources, utilize low-cost electrocatalysts and other inexpensive components in stacks. The sporadic investigation on catalysts and membrane development of AEM electrolysis enable it still under the early stage of development. To enable commercially viable hydrogen generation, deeper understanding and improvement of AEM electrolysis technology is imperative, including power efficiency, stack feasibility, membrane stability, ion conductivity, robustness and cost reduction. In this review, the basic principles, progress and challenges of AEM are discussed. We highlight recent achievements in electrocatalysts, alkaline exchange membranes, ionomers, and the resulting AEM electrolyser performance. In particular, development challenges facing AEM electrolysis are summarized. Hopefully, this review paper will attract additional interest to close technical gaps, while providing practical research recommendations for AEM electrolysis research, leading to scalable hydrogen production.
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•Anion-exchange membranes (AEM) electrolyzers are promising for hydrogen economy.•Basic principles and progresses of main components in AEM system are discussed.•Degradation mechanisms and designing points for AEM electrolyzers are presented.•Practical research recommendations for AEM technology are summarized.
A scalable and low‐cost production of graphene nanoplatelets (GnPs) is one of the most important challenges for their commercialization. A simple mechanochemical reaction has been developed and ...applied to prepare various edge‐functionalized GnPs (EFGnPs). EFGnPs can be produced in a simple and ecofriendly manner by ball milling of graphite with target substances (X = nonmetals, halogens, semimetals, or metalloids). The unique feature of this method is its use of kinetic energy, which can generate active carbon species by unzipping of graphitic CC bonds in dry conditions (no solvent). The active carbon species efficiently pick up X substance(s), leading to the formation of graphitic CX bonds along the broken edges and the delamination of graphitic layers into EFGnPs. Unlike graphene oxide (GO) and reduced GO (rGO), the preparation of EFGnPs does not involve toxic chemicals, such as corrosive acids and toxic reducing agents. Furthermore, the prepared EFGnPs preserve high crystallinity in the basal area due to their edge‐selective functionalization. Considering the available edge X groups that can be selectively employed, the potential applications of EFGnPs are unlimited. In this context, the synthesis, characterizations, and applications of EFGnPs, specifically, as metal‐free carbon‐based electrocatalysts for dye‐sensitized solar cells (DSSCs) in both cobalt and iodine electrolytes are reviewed.
Edge‐functionalized graphene nanoplatelets (EFGnPs), as counter electrode (CE) materials, have demonstrated an excellent performance for dye‐sensitized solar cells (DSSCs). Specific edge groups can provide electrocatalytic active sites for iodine and cobalt reduction reactions. Given the promising potential in metal‐free CEs, research directions are suggested to discover more efficient functional groups and to realize metal‐free‐carbon‐based DSSCs.
Hydrogen peroxide (H2O2) is an environment‐friendly and efficient oxidant with a wide range of applications in different industries. Recently, the production of hydrogen peroxide through direct ...electrosynthesis has attracted widespread research attention, and has emerged as the most promising method to replace the traditional energy‐intensive multi‐step anthraquinone process. In ongoing efforts to achieve highly efficient large‐scale electrosynthesis of H2O2, carbon‐based materials have been developed as 2e− oxygen reduction reaction catalysts, with the benefits of low cost, abundant availability, and optimal performance. This review comprehensively introduces the strategies for optimizing carbon‐based materials toward H2O2 production, and the latest advances in carbon‐based hybrid catalysts. The active sites of the carbon‐based materials and the influence of coordination heteroatom doping on the selectivity of H2O2 are extensively analyzed. In particular, the appropriate design of functional groups and understanding the effect of the electrolyte pH are expected to further improve the selective efficiency of producing H2O2 via the oxygen reduction reaction. Methods for improving catalytic activity by interface engineering and reaction kinetics are summarized. Finally, the challenges carbon‐based catalysts face before they can be employed for commercial‐scale H2O2 production are identified, and prospects for designing novel electrochemical reactors are proposed.
The latest advances in carbon‐based hybrid catalysts toward hydrogen peroxide (H2O2) production are reviewed. In particular, the design of functional groups and the dependence of electrolyte pH play important roles to further improve the selectivity of H2O2 production via the oxygen reduction reaction.
Abstract
The one-step electrochemical synthesis of H
2
O
2
is an on-site method that reduces dependence on the energy-intensive anthraquinone process. Oxidized carbon materials have proven to be ...promising catalysts due to their low cost and facile synthetic procedures. However, the nature of the active sites is still controversial, and direct experimental evidence is presently lacking. Here, we activate a carbon material with dangling edge sites and then decorate them with targeted functional groups. We show that quinone-enriched samples exhibit high selectivity and activity with a H
2
O
2
yield ratio of up to 97.8 % at 0.75 V vs. RHE. Using density functional theory calculations, we identify the activity trends of different possible quinone functional groups in the edge and basal plane of the carbon nanostructure and determine the most active motif. Our findings provide guidelines for designing carbon-based catalysts, which have simultaneous high selectivity and activity for H
2
O
2
synthesis.
A facile approach has been developed to prepare B,N co‐doped graphene with tuneable composition simply by thermal annealing graphene oxide in the presence of boric acid and ammonia. The resultant BCN ...graphene (see picture; C gray, H white, B pink, N blue) has superior electrocatalytic activity over commercial Pt/C electrocatalysts for the oxygen reduction reaction in alkaline media.
It is estimated that the world will need to double its energy supply by 2050. Nanotechnology has opened up new frontiers in materials science and engineering to meet this challenge by creating new ...materials, particularly carbon nanomaterials, for efficient energy conversion and storage. Comparing to conventional energy materials, carbon nanomaterials possess unique size‐/surface‐dependent (e.g., morphological, electrical, optical, and mechanical) properties useful for enhancing the energy‐conversion and storage performances. During the past 25 years or so, therefore, considerable efforts have been made to utilize the unique properties of carbon nanomaterials, including fullerenes, carbon nanotubes, and graphene, as energy materials, and tremendous progress has been achieved in developing high‐performance energy conversion (e.g., solar cells and fuel cells) and storage (e.g., supercapacitors and batteries) devices. This article reviews progress in the research and development of carbon nanomaterials during the past twenty years or so for advanced energy conversion and storage, along with some discussions on challenges and perspectives in this exciting field.
Progress in the research and development of carbon nanomaterials during the past twenty years or so is reviewed with reference to their use in advanced energy conversion and storage applications. Some discussion of the challenges and perspectives in this exciting field is also presented.
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