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Electrochemical C–C and C–N coupling reactions with the conversion of abundant and inexpensive small molecules, such as CO2 and nitrogen‐containing species, are considered a promising route for increasing the value of CO2 reduction products. The development of high‐performance catalysts is the key to the both electrocatalytic reactions. In this review, we present a systematic summary of the reaction systems for electrocatalytic CO2 reduction, along with the coupling mechanisms of C–C and C–N bonds over outstanding electrocatalytic materials recently developed. The key intermediate species and reaction pathways related to the coupling as well as the catalyst‐structure relationship will be also discussed, aiming to provide insights and guidance for designing efficient CO2 reduction systems. [ABSTRACT FROM AUTHOR]

The excessive use of nonrenewable energy has brought about serious greenhouse effect. Converting CO2 into high‐value‐added chemicals is undoubtedly the best choice to solve energy problems. Due to the excellent cost‐effectiveness and dramatic catalytic performance, nickel‐based catalysts have been considered as the most promising candidates for the electrocatalytic CO2 reduction reaction (eCO2RR). In this work, the electrocatalytic reduction mechanism of CO2 over Ni‐based materials is reviewed. The strategies to improve the eCO2RR performance are emphasized. Moreover, the research on Ni‐based materials for syngas generation is briefly summarized. Finally, the prospects of nickel‐based materials in the eCO2RR are provided with the hope of improving transition‐metal‐based electrocatalysts for eCO2RR in the future. [ABSTRACT FROM AUTHOR]

Compared to the Haber–Bosch (H–B) process for ammonia synthesis with massive emission of greenhouse CO2 and necessary harsh reaction conditions, the electrocatalytic NO3− reduction (NO3RR) for ammonia synthesis under ambient temperature and pressure driven by renewable electricity has attracted great attention. NO3RR is also a promising route to construct nitrogen cycles utilizing NOx produced from industrial and agricultural operations. Cu‐based catalyst is one of the most promising platforms for this reaction. This perspective shows the latest understanding and research advances on the NO3RR by Cu‐based electrocatalysts. Through a deep analysis on the rate‐limiting step of NO3RR, the strategies of overcoming the deactivation and enhancing the performance of Cu‐based catalysts are discussed. The great significance of synergistic NOx and H activation in promoting the key kinetic step of electrocatalytic NO3RR by single‐atom, oxide, bimetallic of Cu on the catalytic reaction site construction with tunable adsorption of N‐containing intermediate and active H is stressed. Also, future challenges and perspectives toward coupling reaction of nitrate reduction catalyzed by Cu‐based catalysts are proposed. This perspective can move forward the future research on electrocatalytic NO3RR to ammonia synthesis over advanced Cu‐based electrocatalysts. [ABSTRACT FROM AUTHOR]

The effective non‐precious metal catalysts toward the oxygen evolution reaction (OER) are highly desirable for electrochemical water splitting. Herein, we prepare a novel glass‐ceramic (Ni1.5Sn@triMPO4) by embedding crystalline Ni1.5Sn nanoparticles into amorphous trimetallic phosphate (triMPO4) matrix. This unique crystalline‐amorphous nanostructure synergistically accelerates the surface reconstruction to active Ni(Fe)OOH, due to the low vacancy formation energy of Sn in glass‐ceramic and high adsorption energy of PO43− at the VO sites. Compared to the control samples, this dual‐phase glass‐ceramic exhibits a remarkably lowered overpotential and boosted OER kinetics after surface reconstruction, rivaling most of state‐of‐the‐art electrocatalysts. The residual PO43− and intrinsic VO sites induce redistribution of electron states, thus optimizing the adsorption of OH* and OOH* intermediates on metal oxyhydroxides and promoting the OER activity. [ABSTRACT FROM AUTHOR]

The development of an efficient electrocatalyst toward the hydrogen evolution reaction (HER) is of significant importance in transforming renewable electricity to pure and clean hydrogen by water splitting. However, the construction of an active electrocatalyst with multiple sites that can promote the dissociation of water molecules still remains a great challenge. Herein, a partial‐single‐atom, partial‐nanoparticle composite consisting of nanosized ruthenium (Ru) nanoparticles (NPs) and individual Ru atoms as an energy‐efficient HER catalyst in alkaline medium is reported. The formation of this unique composite mainly results from the dispersion of Ru NPs to small‐size NPs and single atoms (SAs) on the Fe/N codoped carbon (Fe–N–C) substrate due to the thermodynamic stability. The optimal catalyst exhibits an outstanding HER activity with an ultralow overpotential (9 mV) at 10 mA cm−2 (η10), a high turnover frequency (8.9 H2 s−1 at 50 mV overpotential), and nearly 100% Faraday efficiency, outperforming the state‐of‐the‐art commercial Pt/C and other reported HER electrocatalysts in alkaline condition. Both experimental and theoretical calculations reveal that the coexistence of Ru NPs and SAs can improve the hydride coupling and water dissociation kinetics, thus synergistically enhancing alkaline hydrogen evolution performance. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is key to renewable energy technologies such as water electrolysis and metal–air batteries. However, the multiple steps associated with proton‐coupled electron transfer result in sluggish OER kinetics and catalysts are required. Here we demonstrate that a novel nitride, Ni2Mo3N, is a highly active OER catalyst that outperforms the benchmark material RuO2. Ni2Mo3N exhibits a current density of 10 mA cm−2 at a nominal overpotential of 270 mV in 0.1 m KOH with outstanding catalytic cyclability and durability. Structural characterization and computational studies reveal that the excellent activity stems from the formation of a surface‐oxide‐rich activation layer (SOAL). Secondary Mo atoms on the surface act as electron pumps that stabilize oxygen‐containing species and facilitate the continuity of the reactions. This discovery will stimulate the further development of ternary nitrides with oxide surface layers as efficient OER catalysts for electrochemical energy devices. [ABSTRACT FROM AUTHOR]

The development of Pt‐free catalysts for the alkaline hydrogen evolution reaction (HER), which is widely used in industrial scale water‐alkali electrolyzers, remains a contemporary and pressing challenge. Ruthenium (Ru) has excellent water‐dissociation abilities and could be an alternative water splitting catalyst. However, its large hydrogen binding energy limits HER activity. Here, a new approach is proposed to boost the HER activity of Ru through uniform loading of Ru nanoparticles on triazine‐ring (C3N3)‐doped carbon (triNC). The composite (Ru/triNC) exhibits outstanding HER activity with an ultralow overpotential of ≈2 mV at 10 mA cm−2; thereby making it the best performing electrocatalyst hitherto reported for alkaline HER. The calculated metal mass activity of Ru/triNC is >10 and 15 times higher than that of Pt/C and Pt/triNC. Both theoretical and experimental studies reveal that the triazine‐ring is a good match for Ru to weaken the hydrogen binding on Ru through interfacial charge transfer via increased contact electrification. Therefore, Ru/triNC can provide the optimal hydrogen adsorption free energy (approaching zero), while maintaining the strong water‐dissociation activity. This study provides a new avenue for designing highly efficient and stable electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting, as one of the most promising methods to store renewable energy generated by intermittent sources, such as solar and wind energy, has attracted tremendous attention in recent years. Developing efficient, robust, and green catalysts for the hydrogen and oxygen evolution reactions (HER and OER) is of great interest. This study concerns a facile and green approach for producing RuNi/RuNi oxide nanoheterostructures by controllable partial oxidation of RuNi nanoalloy, which is characterized and confirmed by various techniques, including high‐resolution transmission electron microscopy and synchrotron‐based X‐ray absorption spectroscopy. This nanoheterostructure demonstrates outstanding bifunctional activities for catalyzing the HER and OER with overpotentials that are both among the lowest reported values. In a practical alkali–water‐splitting electrolyzer, it also achieves a record‐low cell voltage of 1.42 V at 10 mA cm−2, which is significantly superior to the commercial RuO2//Pt/C couple and other reported bifunctional water‐splitting electrocatalysts. Density functional theory calculations are employed to elaborate the effect of Ni incorporation. This simple catalyst preparation approach is expected to be transferrable to other electrocatalytic reactions. [ABSTRACT FROM AUTHOR]

The replacement of platinum with non-precious-metal electrocatalysts with high efficiency and superior stability for the hydrogen-evolution reaction (HER) remains a great challenge. Herein, we report the one-step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo2C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1-3 layers) showed superior HER activity in acidic media, with a very low onset potential of -6 mV, a small Tafel slope of 41 mV dec-1, and a large exchange current density of 0.179 mA cm-2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state-of-the-art 20% Pt/C and make the catalyst one of the most active acid-stable electrocatalysts ever reported for HER. [ABSTRACT FROM AUTHOR]

The author comments on the importance of the cathodic oxygen reduction reaction (ORR) in companies. The topics discussed include the benefits and detriments of ORR, the attention received by Nitrogen-doped carbons, and the applications of Nitrogen-doping. Moreover, it also cites the reaction of in situ source-template interface reaction.

Transition metal nitrides are of considerable interest for energy conversion and storage applications. Given this, synthesis of nanostructured 3D transition metal nitrides is of contemporary interest. Here, a hard templating simple and efficient pathway to synthesize 3D ordered‐mesoporous ternary nitrides NiCo2N is reported using the mesoporous silica KIT‐6 hard template. Benefitting from its large surface area and accessible pores, uniform shape, and enhanced infiltration capacity for electrolyte, mesoporous NiCo2N demonstrates superior electrode performance for oxygen evolution reaction (OER) in alkaline medium. As‐synthesized mesoporous ternary nitride NiCo2N shows desirable performance with very low overpotential (289 mV), and yields ≈10 mA cm−2 geometric current density. This is lower than the values of IrO2 and that of mesoporous binary nitrides CoN and Ni3N electrocatalysts. NiCo2N shows a small Tafel slope and smallest semicircle. Moreover, as‐synthesized NiCo2N exhibits low loss of activity after 10 h test for OER in alkaline solution. This work explores a promising way to produce OER electrocatalyst Co–Ni‐based ternary nitrides for water splitting applications. [ABSTRACT FROM AUTHOR]

Efficient metal-free electrocatalysts for oxygen reduction reaction (ORR) are highly expected in future low-cost energy systems. We have successfully prepared crumpled, sheet-like, sulfur-doped graphene by magnesiothermic reduction of easily available, low-cost, nontoxic CO2 (in the form of Na2CO3) and Na2SO4 as the carbon and sulfur sources, respectively. At high temperature, Mg can reduce not only carbon in the oxidation state of +4 in CO32− to form graphene, but also sulfur in SO42− from its highest (+6) to lowest valence which was hybridized into the carbon sp2 framework. Various characterization results show that sulfur-doped graphene with only few layers has an appropriate sulfur content, hierarchically robust porous structure, large surface area/pore volume, and highly graphitized textures. The S-doped graphene samples exhibit not only a high activity for ORR with a four-electron pathway, but also superior durability and tolerance to MeOH crossover to 40% Pt/C. This is mainly ascribed to the combination of sulfur-related active sites and hierarchical porous textures, facilitating fast diffusion of oxygen molecules and electrolyte to catalytic sites and release of products from the sites. [ABSTRACT FROM AUTHOR]

Graphical abstract Additional iron doping of N-doped graphene-like carbon sheets results in the formation of highly efficient Fe, N-codoped carbon sheets towards the electrocatalytic oxygen reduction, which also shows better long-term stability and resistance to methanol crossover than commercial Pt/C. Abstract Rational design and synthesis of Fe-N-codoped carbon materials are promising for replacing commercial Pt/C for oxygen reduction reaction (ORR). Herein, we develop a simple two-step pyrolysis approach to synthesize highly active Fe-N-codoped graphene-like carbon sheets (FeNGC) with active Fe-N-based species for ORR. In this strategy, two-dimensional nitrogen-doped graphene-like carbon sheets (NGC) with a high N-doping level (8.1 at%) and abundant mesoporosity (3.8 nm) are firstly synthesized by co-pyrolysis of biomass carbon source and dicyandiamide, in which dicyandiamide simultaneously serves as a trifunctional role of in situ reaction template, nitrogen source and porogen. Secondly, FeNGCs are prepared by additional iron doping of NGC at high temperatures, in which sheet-like structure is in favor of increased accessibility of N-functional groups to more Fe atoms, thus giving rise to formation of high-density Fe-N-based active sites. The optimized catalyst synthesized at 950 °C (FeNGC-950) demonstrates significantly increased ORR activity with a dominant 4e− reduction process compared to pure NGC in alkaline and acidic solutions, which evidently shows the comparable activity to Pt/C due to the synergy of simultaneously optimized structures and multi-active sites. Moreover, FeNGC-950 has better long-term stability and methanol tolerance than Pt/C both in alkaline and acidic electrolytes. The present strategy paves a new venue to design and prepare various metal-doped carbon materials with great potentials in energy applications. [ABSTRACT FROM AUTHOR]

In this paper, a series of nitrogen-doped mesoporous carbons (NMCs) with three-dimensional (3D) interconnected mesopores have been prepared using flour as carbon source, dicyanamide as nitrogen source and colloidal silica as hard template. The optimized material (NMC-4) prepared with the colloidal silica/flour mass ratio of 4 has a high nitrogen doping level of 5.69 at.% and large specific surface area of 995 m 2  g −1 as well as 3D interconnected mesopores (12.9 nm). As the oxygen reduction reaction (ORR) electrocatalyst among various NMCs, NMC-4 exhibits the superior performance and much better stability and methanol crossover with a four-electron dominant reaction pathway compared to commercial 20 wt% Pt/C. Furthermore, as a supercapacitor (SC) electrode material, NMC-4 exhibits a high specific capacitance of 178.5 F g −1 at a current density of 0.5 A g −1 and long cycle life (94.5% capacity retention after 5000 cycles). It also shows a good rate capacity as 76.1% of original specific capacitance remains when the current density increases from 0.5 to 20 A g −1 . The high-performance of NMCs results from the synergetic effects of 3D interconnected mesopores, large surface area, and high N-doping level, enabling fast mass transport and electron transfer during the electrochemical process. This work provides a facile and efficient strategy to heteroatom-doped carbons from extensively available biomass, showing great potentials in electrocatalysis, energy storage, and other applications. [ABSTRACT FROM AUTHOR]

Nitrogen-doped hollow core-mesoporous shelled carbon spheres (NHMCSs) are successfully synthesized via a simple, scalable hydrothermal treatment of hollow mesoporous carbon spheres (HMCSs) with ammonia water as the nitrogen source. This strategy not only efficiently introduces nitrogen atoms into the carbon framework, but also causes the fracture of some spheres and increases the shell thickness of hollow spheres. The subsequent pyrolysis at 900 °C in Ar results in the transformation of pyrrolic-N to graphitic-N. The resulting NHMCS-900 has a high BET specific surface area (648 m 2 g −1 ), large pore volume (1.06 cm 3 g −1 ), hierarchical mesoporosity (2–8, 43.9 nm), uniform shells and large hollow cores. The electrochemical experiments indicate that NHMCS-900 as a metal-free electrocatalyst possesses the improved ORR activity with a close four-electron reaction pathway (∼3.88) and a peroxide yield lower than 10% over a wide potential range in alkaline solution. Contrary to commercial Pt/C, NHMCS-900 is unaffected by the methanol crossover effect and exhibits excellent long-term durability with 97.0% of the initial current density after 5.56 h of continuous operation. The excellent activity of NHMCS-900 is mainly attributed to the high relative content of pyridinic-N and graphitic-N. Besides, the superior activity is also ascribed to its unique structural properties, promoting fast and efficient mass transfer and providing inner and outer surfaces with N-relative active sites for ORR. [ABSTRACT FROM AUTHOR]

Nitrogen-doped porous carbon has aroused extensive interests owing to its unique physical and chemical properties. However, the complicated nitrogen-doping method and high cost limit its practical application. In this work, the nitrogen-rich biomass soybean was used as a single precursor for both carbon and nitrogen source to prepare nitrogen-doped hierarchical micro-mesoporous carbon via templating carbonization coupling with subsequent KOH activation. The influence of KOH dosage on the morphology, structure and electrochemical performance (supercapacitor and oxygen reduction reaction (ORR)) was studied in detail. The optimized ANPC-3, synthesized under the KOH/carbon mass ratio of 3/1, possesses high specific surface area of 1749 m 2  g −1 , developed hierarchical micro-mesoporous structures as well as moderate nitrogen content (1.37 at.%). ANPC-3 exhibits a large energy density of 12.5 Wh kg −1 at a power density of 450 W kg −1 with excellent charge-discharge cyclic stability of 96.5% capacitance remaining after 5000 cycles. As an ORR electrocatalyst, it shows improved ORR activity as well as much better stability and methanol-tolerance capacity than commercial Pt/C catalyst. The unique hierarchical micro-mesoporous textures, high surface area and moderate N-doping level make biomass-derived ANPC-3 become an excellent electrode material in various applications. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) plays a dominant role in proton exchange membrane fuel cells (PEMFCs). Thus, the design and preparation of efficient ORR electrocatalysts is of high importance. In this work, we successfully prepared a series of nitrogen-doped graphene-like carbon nanosheets (NCNSs) with large pore volumes of up to 1.244 cm 3 g −1 and high level of N dopants (5.3–6.8 at%) via a one-step, in-situ reactive template strategy by co-pyrolysis of hydroxypropyl methylcellulose (HPMC) and dicyandiamide (DICY) as the precursors at 1000 °C. The DICY-derived graphitic carbon nitride (g-C 3 N 4 ) nanosheets could act as the hard template for the confined growth of 2D carbon nanosheets, and the further increase in the pyrolysis temperature could directly remove off the g-C 3 N 4 template by complete decomposition and simultaneously dope N atoms within the carbon nanosheets. The pyridinic and graphitic nitrogen groups are dominant among various N functional groups in the NCNSs. The NCNS_1:10 prepared with the HPMC/DICY mass ratio of 1/10 can be used as the metal-free ORR electrocatalysts with optimal activity (onset potential: −0.1 V vs. SCE; limiting current density: 4.8 mA cm −2 ) in O 2 -saturated 0.1 M KOH electrolyte among the NCNSs. Moreover, the NCNS_1:10 demonstrates a dominant four-electron reduction process, as well as excellent long-term operation stability and outstanding methanol crossover resistance. The excellent ORR activity of the NCNS_1:10 should be mainly owing to high contents of pyridinic and graphitic N dopants, large pore volume, hierarchical structures, and microstructural defects. [ABSTRACT FROM AUTHOR]

Developing high-performance anode electrocatalysts is desirable in electrocatalytic energy devices powered by sustainable electricity. Compared to water oxidation using Ni-based anodes, electro-oxidation upgrading of biomass molecule with larger size lacks dynamics driving due to increased thickness and decreased electron transfer kinetics of insulating NiOOH amorphous layer (>50 nm) from uncontrollable in-depth reconstruction. Herein, a self-confined surface reconstruction strategy is proposed to construct ∼5 nm-thick NiOOH layers on NiMo 3 S 4 with superior activity and stability for 5-hydroxymethylfurfural oxidation reaction (HMFOR). In-situ high-valence Mo-O coordination and sulfate-terminated anion groups effectively prevent in-depth surface oxidation, leading to the ultra-thin active layers with increased electron transfer kinetics. The surface self-reconstructed NiMo 3 S 4 (NiMo 3 S 4 -R) exhibits nearly 100% of HMF conversion, FDCA selectivity and Faradaic efficiency, much better than sulfate-modified NiOOH and pure NiOOH. Moreover, a paired electrolyzer of NiMo 3 S 4 -R||NiMo 3 S 4 for HMFOR||HER is also assembled with an ultralow voltage of 1.414 V at 10 mA cm−2. [Display omitted] • Terminated groups of sulfate oxoanions to prevent surface overoxidation of NiMo 3 S 4. • Mo self-doping atoms could partially substitute the Ni site to form (Ni, Mo)OOH. • (Ni, Mo)OOH layer with increased capturing ability for reactants and intermediates. • Surface reconstruction leads low interfacial resistance with fast reaction kinetics. [ABSTRACT FROM AUTHOR]