The development of highly active and stable bifunctional noble‐metal‐based electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is a crucial goal for ...clean and renewable energy, which still remains challenging. Herein, we report an efficient and stable catalyst comprising a Co single atom incorporated in an RuO2 sphere for HER and OER, in which the Co single atom in the RuO2 sphere was confirmed by XAS, AC‐STEM, and DFT. This tailoring strategy uses a Co single atom to modify the electronic structures of the surrounding Ru atoms and thereby remarkably elevates the electrocatalytic activities. The catalyst requires ultralow overpotentials, 45 mV for HER and 200 mV for OER, to deliver a current density of 10 mA cm−2. The theoretical calculations reveal that the energy barriers for HER and OER are lowered after incorporation of a cobalt single atom.
A Co single atom is incorporated in a RuO2 sphere through a one‐pot hydrothermal process, as revealed by EXAFS, HRTEM, and AC‐STEM. The Co single atoms could tailor the local electronic structure of the bifunctional electrocatalyst for high‐performance HER and OER, which significantly reduces the energy barrier, and the catalyst shows the lowest overpotential of 45 mV for HER and 200 mV for OER at a current density of 10 mA cm−2.
Heteroatom‐doped Fe‐NC catalyst has emerged as one of the most promising candidates to replace noble metal‐based catalysts for highly efficient oxygen reduction reaction (ORR). However, delicate ...controls over their structure parameters to optimize the catalytic efficiency and molecular‐level understandings of the catalytic mechanism are still challenging. Herein, a novel pyrrole–thiophene copolymer pyrolysis strategy to synthesize Fe‐isolated single atoms on sulfur and nitrogen‐codoped carbon (Fe‐ISA/SNC) with controllable S, N doping is rationally designed. The catalytic efficiency of Fe‐ISA/SNC shows a volcano‐type curve with the increase of sulfur doping. The optimized Fe‐ISA/SNC exhibits a half‐wave potential of 0.896 V (vs reversible hydrogen electrode (RHE)), which is more positive than those of Fe‐isolated single atoms on nitrogen codoped carbon (Fe‐ISA/NC, 0.839 V), commercial Pt/C (0.841 V), and most reported nonprecious metal catalysts. Fe‐ISA/SNC is methanol tolerable and shows negligible activity decay in alkaline condition during 15 000 voltage cycles. X‐ray absorption fine structure analysis and density functional theory calculations reveal that the incorporated sulfur engineers the charges on N atoms surrounding the Fe reactive center. The enriched charge facilitates the rate‐limiting reductive release of OH* and therefore improved the overall ORR efficiency.
Fe‐isolated single atoms on S, N‐doped carbon (Fe‐ISA/SNC) electrocatalysts with tunable sulfur/nitrogen ratio are synthesized by a novel pyrrole‐co‐thiophene polymer pyrolysis strategy. The electronic modification of the FeNx center by adjacent S atoms enables optimized Fe‐ISA/SNC catalysts with superior activity (E1/2 = 0.896 V) and stability (durable for 15 000 CV cycles) for oxygen reduction reactions.
Controllable synthesis of ultrasmall atomically ordered intermetallic nanoparticles is a challenging task, owing to the high temperature commonly required for the formation of intermetallic phases. ...Here, a metal–organic framework (MOF)‐confined co‐reduction strategy is developed for the preparation of sub‐2 nm intermetallic PdZn nanoparticles, by employing the well‐defined porous structures of calcinated ZIF‐8 (ZIF‐8C) and an in situ co‐reduction therein. HAADF‐STEM, HRTEM, and EDS characterizations reveal the homogeneous dispersion of these sub‐2 nm intermetallic PdZn nanoparticles within the ZIF‐8C frameworks. XRD, XPS, and EXAFS measurements further confirm the atomically ordered intermetallic phase nature of these sub‐2 nm PdZn nanoparticles. Selective hydrogenation of acetylene evaluation results show the excellent catalytic properties of the sub‐2 nm intermetallic PdZn, which result from the energetically more favorable path for acetylene hydrogenation and ethylene desorption over the ultrasmall particles than over larger‐sized intermetallic PdZn as revealed by density functional theory (DFT) calculations. Moreover, this protocol is also extendable for the preparation of sub‐2 nm intermetallic PtZn nanoparticles and is expected to provide a novel methodology in synthesizing ultrasmall atomically ordered intermetallic nanomaterials by rationally functionalizing MOFs.
A metal–organic framework (MOF)‐confined co‐reduction strategy is developed to fabricate sub‐2 nm atomically ordered intermetallic PdZn. The ultrasmall intermetallic PdZn nanoparticles exhibit excellent catalytic properties toward selective hydrogenation of acetylene, derived from the energetically more favorable path for acetylene hydrogenation and ethylene desorption as revealed by density functional theory (DFT) calculations.
Constructing well defined nanostructures is promising but still challenging for high‐efficiency catalysts for hydrogen evolution reaction (HER) and energy storage. Herein, utilizing the differences ...in surface energies between (111) facets of CoP and NiCoP, a novel CoP/NiCoP heterojunction is designed and synthesized with a nanotadpoles (NTs)‐like morphology via a solid‐state phase transformation strategy. By effective interface construction, the disorder in terms of electronic structure and coordination environment at the interface in CoP/NiCoP NTs is created, which leads to dramatically elevated HER performance within a wide pH range. Theoretical calculations prove that an optimized proton chemisorption and H2O dissociation are achieved by an optimized phosphide polymorph at the interface, accelerating the HER reaction. The CoP/NiCoP NTs are also proved to be excellent candidates for use in supercapacitors (SCs) with a high specific capacitance (1106.2 F g−1 at 1 A g−1) and good cycling stability (nearly 100% initial capacity retention after 1000 cycles). An asymmetric supercapacitor shows a high energy density (145 F g−1 at 1 A g−1) and good cycling stability (capacitance retention is 95% after 3200 cycles). This work provides new insights into the catalyst design for electrocatalytic and energy storage applications.
A CoP/NiCoP heterojunction with the unique morphology like nanotadpoles (NTs) is designed and synthesized utilizing the differences in surface energies of the (111) crystal planes between CoP and NiCoP. By effective interface constructing, the CoP/NiCoP NTs exhibit superior electrocatalytic performance for hydrogen evolution within a wide pH range.
For electrocatalysts for the hydrogen evolution reaction (HER), encapsulating transition metal phosphides (TMPs) into nitrogen‐doped carbon materials has been known as an effective strategy to ...elevate the activity and stability. Yet still, it remains unclear how the TMPs work synergistically with the N‐doped support, and which N configuration (pyridinic N, pyrrolic N, or graphitic N) contributes predominantly to the synergy. Here we present a HER electrocatalyst (denoted as MoP@NCHSs) comprising MoP nanoparticles encapsulated in N‐doped carbon hollow spheres, which displays excellent activity and stability for HER in alkaline media. Results of experimental investigations and theoretical calculations indicate that the synergy between MoP and the pyridinic N can most effectively promote the HER in alkaline media.
The effect of the dopant: In the electrocatalyst comprising MoP nanoparticles encapsulated by nitrogen‐doped carbon, the sites where MoP interacts with pyridinic N (but not pyrrolic N or graphitic N) lead to increased electron density on the nitrogen‐doped carbon, as well as optimized adsorption of H* and OH*, all of which help to accelerate the hydrogen evolution reaction in alkaline media.
A coupling catalyst of highly dispersed N, P co‐doped carbon frames (NPCFs) anchored with Fe single atoms (SAs) and Fe2P nanoparticles (NPs) is synthesized by a novel in situ ...doping–adsorption–phosphatization strategy for the electrocatalytic oxygen reduction reaction (ORR). The optimized Fe SAs‐Fe2P NPs/NPCFs‐2.5 catalyst shows a superior ORR activity and stability in 0.5 m H2SO4 and 0.1 m KOH, respectively. Theoretical calculations reveal a synergistic effect, in that the existence of Fe2P weakens the adsorption of ORR intermediates on active sites and lowers the reaction free energy. The doped P atoms with a strong electron‐donating ability elevate the energy level of Fe‐3d orbitals and facilitate the adsorption of O2. The active Fe atoms exist in a low oxidation state and are less positively charged, and they serve as an electron reservoir capable of donating and releasing electrons, thus improving the ORR activity. Operando and in situ characterization results indicate that the atomically dispersed FeN4/FeP coupled active centers in the Fe SAs‐Fe2P NPs/NPCFs‐2.5 catalyst are characteristic of the different catalytic mechanisms in acidic and alkaline media. This work proposes a novel idea for constructing coupling catalysts with atomic‐level precision and provides a strong reference for the development of high‐efficiency ORR electrocatalysts for practical application.
A novel in situ doping–adsorption–phosphidation strategy is discovered for the synthesis of well‐defined Fe single atoms–Fe2P nanoparticles/N, P co‐doped carbon frames catalyst, and a new concept of “atomically dispersed FeN4/FeP coupled active centers” for electrocatalytic oxygen reduction reaction is put forward.
Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to ...fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.
High‐performance, fully atomically dispersed single‐atom catalysts (SACs) are promising candidates for next‐generation industrial catalysts. However, it remains a great challenge to avoid the ...aggregation of isolated atoms into nanoparticles during the preparation and application of SACs. Here, the evolution of Pd species is investigated on different crystal facets of CeO2, and vastly different behaviors on the single‐atomic dispersion of surface Pd atoms are surprisingly discovered. In situ X‐ray photoelectron spectroscopy (XPS), in situ near‐ambient‐pressure‐XPS (NAP‐XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X‐ray absorption spectroscopy (XAS) reveal that, in a reducing atmosphere, more oxygen vacancies are generated on the (100) facet of CeO2, and Pd atoms can be trapped and thus feature atomic dispersion; by contrast, on the CeO2 (111) facet, Pd atoms will readily aggregate into clusters (Pdn). Furthermore, Pd1/CeO2(100) gives a high selectivity of 90.3% for the catalytic N‐alkylation reaction, which is 2.8 times higher than that for Pdn/CeO2(111). This direct evidence demonstrates the crucial role of crystal‐facet effects in the preparation of metal‐atom‐on‐metal‐oxide SACs. This work thus opens an avenue for the rational design and targeted synthesis of ultrastable and sinter‐resistant SACs.
The distinct behaviors of single Pd atoms dispersed on different crystal facets of CeO2 is investigated. In situ characterizations reveal that the oxygen defects on the different facets of CeO2 can affect the formation and stability of single atoms. Pd atoms dispersed on CeO2(100) exhibit higher sinter‐resistant performance than those on CeO2(111), and a different selectivity in the N‐alkylation reaction.
Tungsten‐based catalysts are promising candidates to generate hydrogen effectively. In this work, a single‐W‐atom catalyst supported on metal–organic framework (MOF)‐derived N‐doped carbon (W‐SAC) ...for efficient electrochemical hydrogen evolution reaction (HER), with high activity and excellent stability is reported. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy analysis indicate the atomic dispersion of the W species, and reveal that the W1N1C3 moiety may be the favored local structure for the W species. The W‐SAC exhibits a low overpotential of 85 mV at a current density of 10 mA cm−2 and a small Tafel slope of 53 mV dec−1, in 0.1 m KOH solution. The HER activity of the W‐SAC is almost equal to that of commercial Pt/C. Density functional theory (DFT) calculation suggests that the unique structure of the W1N1C3 moiety plays an important role in enhancing the HER performance. This work gives new insights into the investigation of efficient and practical W‐based HER catalysts.
A single‐tungsten‐atom catalyst supported on metal–organic framework‐derived N‐doped carbon is reported. The catalyst demonstrates a high activity and excellent stability for efficient electrochemical hydrogen evolution.
Developing an efficient single‐atom material (SAM) synthesis and exploring the energy‐related catalytic reaction are important but still challenging. A polymerization–pyrolysis–evaporation (PPE) ...strategy was developed to synthesize N‐doped porous carbon (NPC) with anchored atomically dispersed Fe‐N4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe‐N4 site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn–air battery devices containing the Fe‐N4 SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.
Single‐atom catalyst: A polymerization–pyrolysis–evaporation (PPE) strategy was developed to synthesize N‐doped porous carbon (NPC) with anchored atomically dispersed Fe‐N4 sites. This material is a superior trifunctional catalyst for overall water splitting and Zn–air batteries. The PPE method is a general strategy for preparing M SAs/NPC (M=Fe, Co, Ni, Mn) materials.
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