Heteroatom‐doping in metal‐nitrogen‐carbon single‐atom catalysts (SACs) is considered a powerful strategy to promote the electrocatalytic CO2 reduction reaction (CO2RR), but the origin of enhanced ...catalytic activity is still elusive. Here, we disclose that sulfur doping induces an obvious proton‐feeding effect for CO2RR. The model SAC catalyst with sulfur doping in the second‐shell of FeN4 (Fe1−NSC) was verified by X‐ray absorption spectroscopy and aberration‐corrected scanning transmission electron microscopy. Fe1−NSC exhibits superior CO2RR performance compared to sulfur‐free FeN4 and most reported Fe‐based SACs, with a maximum CO Faradaic efficiency of 98.6 % and turnover frequency of 1197 h−1. Kinetic analysis and in situ characterizations confirm that sulfur doping accelerates H2O activation and feeds sufficient protons for promoting CO2 conversion to *COOH, which is also corroborated by the theoretical results. This work deepens the understanding of the CO2RR mechanism based on SAC catalysts.
Sulfur‐doping in the second coordination shell of FeN4 induces the increased CO2 reduction reaction (CO2RR) performance relative to pristine FeN4. The proton‐feeding effect after sulfur doping is demonstrated to promote protonation of *CO2 to *COOH, and thus CO2RR performances, through kinetic analysis, in situ characterization and DFT calculations.
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The electrochemical nitrogen reduction reaction (NRR) process usually suffers extremely low Faradaic efficiency and ammonia yields due to sluggish NN dissociation. Herein, single‐atomic ruthenium ...modified Mo2CTX MXene nanosheets as an efficient electrocatalyst for nitrogen fixation at ambient conditions are reported. The catalyst achieves a Faradaic efficiency of 25.77% and ammonia yield rate of 40.57 µg h−1 mg−1 at ‐0.3 V versus the reversible hydrogen electrode in 0.5 m K2SO4 solution. Operando X‐ray absorption spectroscopy studies and density functional theory calculations reveal that single‐atomic Ru anchored on MXene nanosheets act as important electron back‐donation centers for N2 activation, which can not only promote nitrogen adsorption and activation behavior of the catalyst, but also lower the thermodynamic energy barrier of the first hydrogenation step. This work opens up a promising avenue to manipulate catalytic performance of electrocatalysts utilizing an atomic‐level engineering strategy.
Single‐atomic ruthenium modified Mo2CTX MXene nanosheets are developed as an efficient electrocatalyst for nitrogen fixation under ambient conditions. The catalyst achieves a high Faradaic efficiency and a large ammonia yield rate in 0.5 m K2SO4 solution, outperforming many previous reported nitrogen reduction reaction electrocatalysts. The high activity and durability enable the single‐atomic Ru‐Mo2CTX to be a promising electrocatalyst for artificial nitrogen fixation.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To improve the electroactivity and stability of electrocatalysts, various modulation strategies have been applied in nanocatalysts. Among different methods, heteroatom doping has been considered as ...an effective method, which modifies the local bonding environments and the electronic structures. Meanwhile, the design of novel two‐dimensional (2D) nanostructures also offers new opportunities for achieving efficient electrocatalysts. In this work, Mn‐doped ultrathin Ru nanosheet branches (RuMn NSBs), a newly reported 2D nanostructure, is synthesized. With the ultrathin and naturally abundant edges, the RuMn NSBs have exhibited bifunctionalities of hydrogen evolution reaction and oxygen evolution reaction with high electroactivity and durability in different electrolytes. Experimental characterizations have revealed that RuO bonds are shortened due to Mn doping, which is the key factor that leads to improved electrochemical performances. Density functional theory (DFT) calculations have confirmed that the introduction of Mn enables flexible modulations on the valence states of Ru sites. The inversed redox state evolutions of Ru and Mn sites not only improve the electroactivity for the water splitting but also the long‐term stability due to the pinning effect of Ru sites. This work has provided important inspirations for the design of future advanced Ru‐based electrocatalysts with high performances and durability.
Fast site‐to‐site electron transfer is achieved over ultrathin Mn‐doped Ru nanosheet branches due to the compensating electronic effect. Benefiting from the electronic modification and structural merits, high electroactivity, and durable stability for overall water splitting in acidic media are realized for the Mn‐doped Ru nanosheet branches.
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Ruthenium (Ru)‐based catalysts, with considerable performance and desirable cost, are becoming highly interesting candidates to replace platinum (Pt) in the alkaline hydrogen evolution reaction ...(HER). The hydrogen binding at Ru sites (Ru−H) is an important factor limiting the HER activity. Herein, density functional theory (DFT) simulations show that the essence of Ru−H binding energy is the strong interaction between the 4dz2
orbital of Ru and the 1s orbital of H. The charge transfer between Ru sites and substrates (Co and Ni) causes the appropriate downward shift of the 4dz2
‐band center of Ru, which results in a Gibbs free energy of 0.022 eV for H* in the RuCo system, much lower than the 0.133 eV in the pure Ru system. This theoretical prediction has been experimentally confirmed using RuCo alloy‐nanosheets (RuCo ANSs). They were prepared via a fast co‐precipitation method followed with a mild electrochemical reduction. Structure characterizations reveal that the Ru atoms are embedded into the Co substrate as isolated active sites with a planar symmetric and Z‐direction asymmetric coordination structure, obtaining an optimal 4dz2
modulated electronic structure. Hydrogen sensor and temperature program desorption (TPD) tests demonstrate the enhanced Ru−H interactions in RuCo ANSs compared to those in pure Ru nanoparticles. As a result, the RuCo ANSs reach an ultra‐low overpotential of 10 mV at 10 mA cm−2 and a Tafel slope of 20.6 mV dec−1 in 1 M KOH, outperforming that of the commercial Pt/C. This holistic work provides a new insight to promote alkaline HER by optimizing the metal‐H binding energy of active sites.
Optimizing Ru−H adsorption/desorption efficiency, via adjusting the Ru 4dz2
orbital in RuCo alloy‐nanosheets, enables highly promoted alkaline hydrogen evolution reaction. This optimized adsorption/desorption efficiency is demonstrated by the hydrogen sensor and temperature programmed desorption experiments. The RuCo alloy‐nanosheets possess a record low overpotential of 10 mV at 10 mA cm−2, superior to the commercial Pt/C and Ru/C.
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Abstract
Maximizing the catalytic activity of single-atom catalysts is vital for the application of single-atom catalysts in industrial water-alkali electrolyzers, yet the modulation of the catalytic ...properties of single-atom catalysts remains challenging. Here, we construct strain-tunable sulphur vacancies around single-atom Ru sites for accelerating the alkaline hydrogen evolution reaction of single-atom Ru sites based on a nanoporous MoS
2
-based Ru single-atom catalyst. By altering the strain of this system, the synergistic effect between sulphur vacancies and Ru sites is amplified, thus changing the catalytic behavior of active sites, namely, the increased reactant density in strained sulphur vacancies and the accelerated hydrogen evolution reaction process on Ru sites. The resulting catalyst delivers an overpotential of 30 mV at a current density of 10 mA cm
−2
, a Tafel slope of 31 mV dec
−1
, and a long catalytic lifetime. This work provides an effective strategy to improve the activities of single-atom modified transition metal dichalcogenides catalysts by precise strain engineering.
Abstract
Iron phthalocyanine (FePc) is a promising non-precious catalyst for the oxygen reduction reaction (ORR). Unfortunately, FePc with plane-symmetric FeN
4
site usually exhibits an ...unsatisfactory ORR activity due to its poor O
2
adsorption and activation. Here, we report an axial Fe–O coordination induced electronic localization strategy to improve its O
2
adsorption, activation and thus the ORR performance. Theoretical calculations indicate that the Fe–O coordination evokes the electronic localization among the axial direction of O–FeN
4
sites to enhance O
2
adsorption and activation. To realize this speculation, FePc is coordinated with an oxidized carbon. Synchrotron X-ray absorption and Mössbauer spectra validate Fe–O coordination between FePc and carbon. The obtained catalyst exhibits fast kinetics for O
2
adsorption and activation with an ultralow Tafel slope of 27.5 mV dec
−1
and a remarkable half-wave potential of 0.90 V. This work offers a new strategy to regulate catalytic sites for better performance.
The electrocatalytic nitrogen reduction reaction (NRR) provides a promising strategy to convert the abundant but inert N2 into NH3 using renewable energy. Herein, single‐atom Au isolated onto ...bicontinous nanoporous MoSe2 (np‐MoSe2) is designed as an electrocatalyst for achieving highly efficient NRR catalysis, which exhibits a high Faradaic efficiency (FE) of 37.82% and an NH3 production rate of 30.83 µg h−1 mg−1 at –0.3 V versus a reversible hydrogen electrode (RHE) in 0.1 m Na2SO4 under ambient conditions. Experimental and theoretical investigations reveal that the introduction of single Au atoms onto np‐MoSe2 optimizes the adsorption of NRR intermediates while suppressing the competing HER, thus providing an energetic‐favorable process for enhancing the catalytic selectivity toward electrochemical N2 reduction into NH3.
Single Au atoms/clusters isolated onto nanoporous MoSe2 catalyst is constructed by the combination of chemical vapor deposition (CVD) process and chemical etching. The resulting catalyst is highly active and stable toward electrochemical nitrogen reduction with a much higher ammonia yield (30.83 µg h−1 mg−1) and Faradaic efficiency (FE, 37.82%) than well‐studied Mo‐based catalysts. This work not only paves a favorable avenue for exploring and designing single‐atoms anchored onto 2D materials, but also provides insights into regulating the reaction pathway for the nitrogen reduction reaction (NRR).
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Designing efficient single-atom catalysts (SACs) for oxygen evolution reaction (OER) is critical for water-splitting. However, the self-reconstruction of isolated active sites during OER not only ...influences the catalytic activity, but also limits the understanding of structure-property relationships. Here, we utilize a self-reconstruction strategy to prepare a SAC with isolated iridium anchored on oxyhydroxides, which exhibits high catalytic OER performance with low overpotential and small Tafel slope, superior to the IrO
. Operando X-ray absorption spectroscopy studies in combination with theory calculations indicate that the isolated iridium sites undergo a deprotonation process to form the multiple active sites during OER, promoting the O-O coupling. The isolated iridium sites are revealed to remain dispersed due to the support effect during OER. This work not only affords the rational design strategy of OER SACs at the atomic scale, but also provides the fundamental insights of the operando OER mechanism for highly active OER SACs.
Designing efficient electrocatalysts for hydrogen evolution reaction is significant for renewable and sustainable energy conversion. Here, we report single-atom platinum decorated nanoporous Co
Se ...(Pt/np-Co
Se) as efficient electrocatalysts for hydrogen evolution. The achieved Pt/np-Co
Se shows high catalytic performance with a near-zero onset overpotential, a low Tafel slope of 35 mV dec
, and a high turnover frequency of 3.93 s
at -100 mV in neutral media, outperforming commercial Pt/C catalyst and other reported transition-metal-based compounds. Operando X-ray absorption spectroscopy studies combined with density functional theory calculations indicate that single-atom platinum in Pt/np-Co
Se not only can optimize surface states of Co
Se active centers under realistic working conditions, but also can significantly reduce energy barriers of water dissociation and improve adsorption/desorption behavior of hydrogen, which synergistically promote thermodynamics and kinetics. This work opens up further opportunities for local electronic structures tuning of electrocatalysts to effectively manipulate its catalytic properties by an atomic-level engineering strategy.
Layered AxCoO2 materials built by stacking layers of CoO2 slabs and inserting alkali ions in between them have shown a promising activity of oxygen evolution reaction (OER) due to their active edge ...sites. However, the large basal plane areas of the CoO2 slabs show too strong adsorption energy to the reaction intermediates, which is unfavorable for the release of O2. Here, a simple cation‐exchange strategy based on Fe3+ and alkali ions is proposed to simultaneously activate both the basal plane and edge sites of AxCoO2 for the OER. X‐ray absorption spectroscopy has revealed that the Fe3+ ions deposit both on the surface and edge sites of the CoO2 slabs and enter the interlayer. The cation‐exchanged AxCoO2 electrodes show a boosted activity compared to their pristine and conventional Fe‐doped AxCoO2 counterparts. This phenomenon is mainly ascribed to the abundant edge‐sharing Co–Fe motifs at the edge sites and the charge redistribution in the basal plane sites induced by the insertion of Fe3+ ions. This work provides a novel method to fully exploit layer‐structured materials for efficient energy conversion.
A cation‐exchange strategy is proposed to simultaneously activate both the basal plane and edge sites of layered cobalt materials for the oxygen evolution reaction (OER). The as‐prepared materials show better OER activity than the pristine and conventional‐doped materials. This work provides a facile and controllable way to boost the OER performance of the layer structured materials.
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