Figure - available from: Advanced Materials
This content is subject to copyright. Terms and conditions apply.
N,S‐doped graphene foam for HER. a) SEM image and b) cyclic voltammetry of sample prepared at different temperatures under CVD. a,b) Adapted with permission.49 Copyright 2015, Wiley‐VCH. N,P‐doped porous carbon for ORR and OER. c) Schematic of N,P‐doped porous carbon and d) linear scan voltammetry in 0.1 m KOH show ORR and OER activity. e) Schematic of a Zn–air battery where the N,P‐doped porous carbon is coupled to the Zn anode. f) Polarization and power density curves of Zn–air batteries with different ORR catalysts. c–f) Adapted with permission.53 Copyright 2015, Springer Nature.
Source publication
With the advent of carbon nanotechnology, which initiated significant research efforts more than two decades ago, novel materials for energy harvesting and storage have emerged at an amazing pace. Nevertheless, some fundamental applications are still dominated by traditional materials, and it is especially evident in the case of catalysis, and envi...
Citations
... As described by Raman spectroscopy, the intensity ratio of the D-band to the G-band (I D /I G ) of the a-ZnS/Fe-NSC (0.98) is higher than that of Fe-NSC (0.95), indicating Zn-assisted thermal treatment produced defects (Supplementary Fig. 7)25, 26 . The electron paramagnetic resonance (EPR) results also supported this result (Supplementary Fig. 8)27, 28 .Transmission electron microscopy (TEM) images show ZnS loaded on carbon nanosheets(Fig. 2b). ...
The M-N x single-atom catalysts (SACs) are critical for efficient energy conversion technologies. However, most SACs with M-N x moiety (M: Fe, Co, or/and Mn) suffer the strong binding ability with OH* intermediates in oxygen reduction reaction (ORR), which becomes a bottleneck in accelerating the kinetics. Herein, a universal “space-charged localization effect” strategy is proposed by constructing a p- n junction, where an n -type ZnS semiconductor longitudinally bridges with p -type M-N x moiety to weaken the interaction of M-Nx with OH*. As expected, the a -ZnS/Fe-NSC electrocatalyst exhibits remarkable intrinsic activity in alkaline media with a half-wave potential of 0.90 V vs. RHE, and long-term durability (a shift of only 10 mV in E 1/2 after 8,000 cycles). This phenomenon can be ascribed to the optimization of electronic structure, the S-MN 4 site can effectively activate the M center with the intermediate spin state which possesses one eg electron (t 2g 4 e g 1) readily penetrating the antibonding π-orbital of oxygen. Moreover, it offers a superior power density and higher discharge voltage in Al-air batteries. This universal strategy provides a rational perspective for the design of SACs and electronic structure engineering to construct robust active sites for high-performance oxygen reduction.
... In addition, the moderate adsorption ability of the catalyst for the intermediate product FA should be considered for its continuous and sequenced reaction feature. Nonmetallic heteroatom (B, N, P, or S) modification of nanocarbon has been proven as an effective means to adjust the surface characteristics and redox/acidic catalytic activity of nanocarbon catalysts [22][23][24][25] . For example, N,O-co-doped onion-like carbon (OLC) has exhibited a high DMM selectivity of 75% with long-term stability over 10 h 13 . ...
... [16,17] Recently, the contribution of intrinsic structural defects to the catalytic properties of carbon materials is growingly recognized. [18][19][20][21] Of special note is the discovery that calcination of N-doped carbon materials to discharge the N dopants leads to even higher catalytic activity than the pristine doped one. [22,23] By precisely controlling the configuration of N dopants, Yao et al. further revealed that calcination indeed leads to the removal of Pyd-N, leaving the remaining five carbon atoms to reorganize into edged pentagons, whose content is positively correlated with the oxygen reduction reaction (ORR) activity. ...
Doping–dedoping chemistry lays the cornerstone for converting heteroatom dopants into intrinsic defects as the emerging active sites of carbon catalysts, but the defect content is yet hindered by inadequate doping efficiencies. Comprehending crucial factors behind the doping of pristine carbon and their correlation to the catalytic properties of dedoped carbon is thus of high significance. Here, the overlooked impact of native defects in pristine carbon on dopant‐mediated defect engineering of carbon catalysts is explicitly unveiled. Intact fullerene (C60), C60‐derived carbon, and carbon black in distinct pentagon/edge defect states are employed as respective precursors to undergo a nitrogen doping–dedoping treatment. Theoretical and experimental evidence consistently indicates that native pentagons change the preferred N doping site from the edge to the basal plane, leading to a substantially higher doping level. Importantly, in addition to pentagons from the removal of zigzag‐edged pyridinic N, N dopants in in‐plane pentagons are more easily dedoped than those in hexagons, generating even more pentagons in a new pentagon–heptagon–pentagon structure as oxygen reduction active sites. The optimized defect‐rich carbon gives an outstanding half‐wave potential of 0.834 V (0.846 V for Pt/C) via the four‐electron pathway, excellent long‐term durability, and prospective applicability in zinc–air batteries.
... The other is the application of defect engineering. [60,61] The adsorption of oxygen-containing intermediates is favored by defects or disordered structures at the edges or surfaces of CAC materials that break the electron-hole symmetry. Therefore combining heteroatom doping with defect engineering is a commonly used strategy to enhance the catalytic activity of biomass-derived CAC electrocatalysts. ...
The shortage and unevenness of fossil energy sources are affecting the development and progress of human civilization. The technology of efficiently converting material resources into energy for utilization and storage is attracting the attention of researchers. Environmentally friendly biomass materials are a treasure to drive the development of new‐generation energy sources. Electrochemical theory is used to efficiently convert the chemical energy of chemical substances into electrical energy. In recent years, significant progress has been made in the development of green and economical electrocatalysts for oxygen reduction reaction (ORR). Although many reviews have been reported around the application of biomass‐derived catalytically active carbon (CAC) catalysts in ORR, these reviews have only selected a single/partial topic (including synthesis and preparation of catalysts from different sources, structural optimization, or performance enhancement methods based on CAC catalysts, and application of biomass‐derived CACs) for discussion. There is no review that systematically addresses the latest progress in the synthesis, performance enhancement, and applications related to biomass‐derived CAC‐based oxygen reduction electrocatalysts synchronously. This review fills the gap by providing a timely and comprehensive review and summary from the following sections: the exposition of the basic catalytic principles of ORR, the summary of the chemical composition and structural properties of various types of biomass, the analysis of traditional and the latest popular biomass‐derived CAC synthesis methods and optimization strategies, and the summary of the practical applications of biomass‐derived CAC‐based oxidative reduction electrocatalysts. This review provides a comprehensive summary of the latest advances to provide research directions and design ideas for the development of catalyst synthesis/optimization and contributes to the industrialization of biomass‐derived CAC electrocatalysis and electric energy storage.
... Surface defect engineering, such as creating oxygen vacancies with rich localized electrons, is an effective approach to manipulate the surface band structure, which has been widely employed in photocatalysis, 165 electrocatalysis, 166 and thermocatalysis. 167 Similarly, this strategy also provides an effective way to further optimize piezocatalysts for water splitting. ...
... These traditional processes suffer from some inevitable issues, including high energy consumption, catalyst inactivation, and environmental pollution. Carbon-based catalysts are promising alternatives to traditional transition metal and noble metal catalysts in various chemical reactions due to their unique advantages, including their abundant functional groups, tunable porosity, and morphology [4][5][6] . Compared with undoped nanocarbons, nitrogen-doped nanocarbons (NCs) are notable for their superior catalytic performance in the two abovementioned reactions [7][8][9][10] . ...
... Previous studies elucidate that within N-doped biochar, pyridinic-nitrogen emerges as the principal active N species, pivotal in initiating the activation of peroxymonosulfate and facilitating the degradation of ciprofloxacin processes [48]. Consequently, this infers that within this study, the emergence of heterocyclic nitrogen configurations (e.g., pyrrolic, pyridinic, and graphitic nitrogen) subsequent to the further modification of GBC into N-GBC potentially underlies its augmented adsorption capabilities, given the higher reactivity exhibited by these heterocyclic nitrogen species [49]. ...
To improve the adsorption efficiency of pollutants by biochar, preparing graphene-like biochar (GBC) or nitrogen-doped biochar are two commonly used methods. However, the difference in the nitrogen doping (N-doping) effects upon the adsorption of pollutants by pristine biochar (PBC) and GBC, as well as the underlying mechanisms, are still unclear. Take the tetracycline (TC) as an example, the present study analyzed the characteristics of the adsorption of TCs on biochars (PBC, GBC, N-PBC, N-GBC), and significant differences in the effects of N-doping on the adsorption of TCs by PBC and GBC were consistently observed at different solution properties. Specifically, N-doping had varied effects on the adsorption performance of PBC, whereas it uniformly improved the adsorption performance of GBC. To interpret the phenomenon, the N-doping upon the adsorption was revealed by the QSAR model, which indicated that the pore filling (V M) and the interactions between TCs with biochars (E ad-v) were found to be the most important two factors. Furthermore, the density functional theory (DFT) results demonstrated that N-doping slightly affects biochar's chemical reactivity. The van der Waals (vdWs) and electrostatic interactions are the main forces for TCs-biochars interactions. Moreover, N-doping mostly strengthened the electrostatic interactions of TCs-biochars, but the vdWs interactions of most samples remained largely unaffected. Overall, the revealed mechanism of N-doping on TCs adsorption by biochars will enhance our knowledge of antibiotic pollution remediation.
... It has been reported that the asymmetric distribution of the electronic conjugation structure in carbon, modified by oxygen groups (O-groups) or structural defects, is particularly effective for promoting the 2e − ORR activity 8,18,23,[25][26][27] . However, the catalytic contributions of the aforementioned two categories of active sites are frequently indistinguishable because of 1) the coexistence of carbon defects and O-groups on carbons; 2) the ambiguous relationship between carbon defect density and O-groups towards ORR performance; 3) the unclear anchor sites of O-groups on the carbons [28][29][30][31][32][33][34] . While some works have proposed potential active site via manipulating the types and distribution of O-groups or using model catalysts 8,18,23,35 , the potential dynamic structural transformation during electrocatalysis has been overlooked with few reports. ...
Active sites identification in metal-free carbon materials is crucial for developing practical electrocatalysts, but resolving precise configuration of active site remains a challenge because of the elusive dynamic structural evolution process during reactions. Here, we reveal the dynamic active site identification process of oxygen modified defective graphene. First, the defect density and types of oxygen groups were precisely manipulated on graphene, combined with electrocatalytic performance evaluation, revealing a previously overlooked positive correlation relationship between the defect density and the 2 e⁻ oxygen reduction performance. An electrocatalytic-driven oxygen groups redistribution phenomenon was observed, which narrows the scope of potential configurations of the active site. The dynamic evolution processes are monitored via multiple in-situ technologies and theoretical spectra simulations, resolving the configuration of major active sites (carbonyl on pentagon defect) and key intermediates (*OOH), in-depth understanding the catalytic mechanism and providing a research paradigm for metal-free carbon materials.
... [53][54][55] More recently, the preparation of metal-free materials has concentrated on the synthesis methodology for achieving highly strained regions in sp 2 networks; functional and activated nanostructures (O atoms for example); heteroatom doping (N, B alternating electron and active sites); and active sites at defects, vacancy pentagons/heptagons, and edges. 54,56 In this section, we concentrate on the origin of 4-electron transfer in metal-free materials, and their high stability in ZABs. ...
With the growing depletion of traditional fossil energy resources and ongoing enhanced awareness of environmental protection, research on electrochemical energy storage techniques like zinc-air batteries is receiving close attention. A significant amount of work on bifunctional catalysts is devoted to improving OER and ORR reaction performance to pave the way for the commercialization of new batteries. Although most traditional energy storage systems perform very well, their durability in practical applications is receiving less attention, with issues such as carbon corrosion, reconstruction during the OER process, and degradation, which can seriously impact long-term use. To be able to design bifunctional materials in a bottom-up approach, a summary of different kinds of carbon materials and transition metal-based materials will be of assistance in selecting a suitable and highly active catalyst from the extensive existing non-precious materials database. Also, the modulation of current carbon materials, aimed at increasing defects and vacancies in carbon and electron distribution in metal-N-C is introduced to attain improved ORR performance of porous materials with fast mass and air transfer. Finally, the reconstruction of catalysts is introduced. The review concludes with comprehensive recommendations for obtaining high-performance and highly-durable catalysts.
... At the same time, it can also prevent the aggregation of metal particles by synthesizing special structures such as core-shell structure and bamboo structure, protect the active site, and improve the stability of the catalyst. [126,127] The electron density distribution and charge distribution of the catalyst can be changed by introducing defects, for example, edge defects (jagged edges, armchair-like edges, and edge cavity structures) can increase the binding energy of electrons in the catalyst, and vacancy defects often form new connection configurations in the catalyst For example, oxygen vacancies and intermediates can form new active centers by chemical bonding, and vacant active centers can accelerate the dissociation of O 2 and regulate the adsorption of terminal active groups. [128] In addition, the synergy between different strategies can effectively improve the catalytic activity, and the presence of defects can provide anchor points for heteroatom doping, which in turn affects the electron distribution of carbon atoms around the defect. ...
Oxygen reduction reaction (ORR) is the core reaction of fuel cell/metal–air battery at the cathode, and it is of great significance to develop high‐performance ORR catalyst. Generally speaking, ORR catalysts are classified according to the class of materials they use, which often makes it difficult for different types of catalysts to have a clear connection with some unified optimization mechanism and creates difficulties in designing improvement strategies. Here, this review proposes three major strategies that can affect the activity of ORR catalysts: designing morphology, defect control, and heteroatom doping. The core content of this review is to analyze the principles of various optimization strategies that affect the performance of catalysts individually or synergistically at the micro level. In addition, the problems and challenges still faced in the design of ORR catalysts are sorted out, and possible solutions are proposed. This review makes the research direction of ORR catalysts clearer, and provides theoretical support and new ideas for the design of high‐efficiency electrocatalysts.
