The deliberate engineering of the d-band center of metal site represents an effective strategy to boost the intrinsic electrocatalytic performance toward the oxygen reduction reaction (ORR). Herein, following a heterointerface-induced orbital coupling rationale, we report a judicious design of an efficient ORR electrocatalyst consisting of Fe₃O₄/CeO₂ hetero-nanoparticles in situ encased into N-doped carbon nanofibers (abbreviated as Fe₃O₄/CeO₂@N-CNFs hereafter). The theoretic calculations uncover that the Fe₃O₄/CeO₂ heterointerface-triggered orbital coupling can cause the downshift of the d-band center positions of Fe sites, which leads to the weakened chemisorption of oxygenated groups and lowered energy barrier for the potential-determining step, ultimately dramatically boosting the ORR intrinsic activity. As a consequence, the well-designed Fe₃O₄/CeO₂@N-CNFs display admirable ORR activity with a half-wave potential of 0.84 V and outstanding structural/electrochemical stability in an alkaline electrolyte, surpassing the commercial Pt/C benchmark and a majority of recently reported Fe₃O₄-based electrocatalysts. More encouragingly, the Fe₃O₄/CeO₂@N-CNFs-incorporated Zn-air battery outperforms the Pt/C-assembled counterpart with higher power density, larger energy density and excellent cycling stability, serving as a competent candidate for ORR-involved renewable energy setups. This study offers an innovative approach for the rational manipulation of the d-band center and interfacial electron behavior of active sites toward the optimization of electrocatalytic performance.

Atomically-dispersed iron-based electrocatalysts are promising substitutes for noble metal electrocatalysts because of excellent performance in oxygen reduction reaction (ORR). Rationally modulating the local coordination environment of the Fe site and optimizing the binding energy of oxygen reduction intermediates are effective strategies to optimize ORR activity. Herein, we report a new method in which Ni is introduced to construct NiFe dual single atoms and iron nanoclusters loaded on the nitrogen-doped carbon with a highly porous structure. This design plays a synergistic role of dual single atoms and clusters, optimizes the 3d orbital and Fermi level of Fe, breaks the symmetrical structure of Fe-N₄, and effectively improves the adsorption/desorption behavior of the oxygen-containing intermediates. Electrochemical tests show Fe_NCs/NiFe_SAs-NC has an excellent intrinsic activity. Theoretical calculations show the oxygen-containing species on the Ni active site will move to the middle of NiFe (bridge site connection) after optimization and that the key step is OH desorption, with a reaction energy of 0.27 eV. The electron exchange between NiFe-N₆ and Fe-cluster is very strong, further indicating the introduction of Ni species and Fe clusters has a regulatory effect on the electronic structure of Fe-N₄.

The development of highly efficient and stable Pd-based catalysts is crucial to improve their sluggish oxygen reduction reaction (ORR) kinetics in acid media. To improve ORR activity and utilization efficiency of Pd, an ideal catalyst should have ORR-favorable chemical environment, optimized geometric structure, and long periods of operation. In this work, we first synthesize a novel trimetallic Au@PdPb core-shell catalyst consisting of PdPb alloy nano-layers grown on the surface of ultrathin Au nanowires (NWs) by a two-step water-bath method. The Au@PdPb NWs have the merits of anisotropic one-dimensional nanostructure, high utilization efficiency of Pd atoms and doping of Pb atoms. Because of the structural and multiple compositional advantages, Au@PdPb NWs exhibit remarkably enhanced ORR activity with a high haIf-wave potential (0.827 V), much better than those of commercial Pd black (0.788 V) and bimetallic Au@Pd NWs (0.803 V). Moreover, Au@PdPb NWs display better electrocatalytic stability for the ORR than those of Pd black and Au@Pd NWs. This study demonstrates the validity of our approach for deriving highly ORR-active Pd-based catalysts by modifying their structure and composition.

Developing highly efficient bifunctional cathode and anode electrocatalysts is very important for the large-scale application of direct formic acid fuel cells. However, the high-cost and poor CO-tolerance ability of the most commonly used Pt greatly block this process. To increase the utilization efficiency and extend bifunctional properties of precious Pt, herein, coral-like Pt₃Ag nanocrystals are developed as an excellent bifunctional electrocatalyst through a facile one-pot solvothermal method. The formation mechanism of Pt₃Ag nanocorals has been elaborated well via a series of control experiments. It is proved that 1-naphthol serving as a guiding surfactant plays a key role in the formation of high-quality nanocorals. Thanks to the unique coral-like structure and alloy effects, the developed Pt₃Ag nanocorals present significantly enhanced electrocatalytic properties (including activity, stability and CO-tolerance ability) towards both the cathodic oxygen reduction and anodic formic acid oxidation, as compared with those of commercial Pt black and Pt-based nanoparticles. The present synthetic method can also be extended to fabricate other bimetallic electrocatalysts with unique morphology and structure.

A novel carbon-supported cyanogel (C@cyanogel)-derived strategy is used to synthesize an intermetallic Pd₃Fe/C compound of the desired ordered Pd₃Fe phase with a small particle size. The novelty of this work lies in using carbon-supported K₂Pd^IICl₄/K₄Fe^II(CN)₆ cyanogel as a reaction precursor, generated through the substitution of two chloride ligands by the nitrogen ends of the cyanide ligands on the metal center. The inherent nature of cyanogels can effectively suppress the movement of Pd⁰ and Fe⁰ nuclei in the crystal, benefiting the formation of the intermetallic, which is otherwise challenging via traditional synthesis techniques. The ordered Pd₃Fe/C catalyst exhibits excellent catalytic activity and good cycle stability for the formic acid oxidation (FAO) reaction relative to the properties of disordered Pd₃Fe/C and commercial Pd/C catalysts, demonstrating that the ordered Pd₃Fe/C is a promising replacement for commercial Pd-based catalysts. The outstanding performance can be ascribed to the full isolation of active sites in the ordered Pd₃Fe structure and the modified electronic structure of the active components. This work provides an effective and novel route to obtain Pd-based intermetallic compounds with potential applications in a wide range of electrocatalysis.

To address the insufficient electrocatalytic activity and stability of formic acid oxidation reaction (FAOR) electrocatalysts, as well as their high cost, we herein demonstrate the facile hydrothermal synthesis of ultrathin AgPt alloy nanowires using amine-terminated poly(N-isopropylacrylamide) (PNIPAM-NH₂) as a structure-directing agent. The initial generation of AgCl precipitates, subsequent formation of AgPt nanoparticles, and their oriented attachment account for the formation of ultrathin AgPt alloy nanowires. Benefiting from their unique 1D anisotropy and alloyed composition, the prepared ultrathin AgPt nanowires exhibit a superior electrocatalytic activity and better CO tolerance for the FAOR, reaching a 1.6-fold and 3.7-fold higher specific current density than AgPt nanoparticles and a commercial Pt black catalyst, respectively. Additionally, the ultrathin AgPt alloy nanowires manifest a superior electrochemical stability and structural robustness during electrocatalysis, making them a promising FAOR electrocatalyst. This work not only provides a reliable strategy for the synthesis of noble metal-based ultrathin nanowires, but also opens an avenue towards the rational design of efficient electrocatalysts for fuel cell systems.

Although nanostructures based on noble metal alloys are widely utilized in (electro)catalysis, their low-temperature synthesis remains an enormous challenge due to the different Nernst equilibrium potentials of metal precursors. Herein, we describe the successful synthesis of trimetallic PtRhNi alloy nanoassemblies (PtRhNi-ANAs) with tunable Pt/Rh ratios using a simple mixed cyanogel reduction method and provide a detailed characterization of their chemical composition, morphology, and structure. Additionally, the electrochemical properties of PtRhNi-ANAs are examined by cyclic voltammetry, revealing composition-dependent electrocatalytic activity in the ethanol oxidation reaction (EOR). Compared to a commercial Pt black electrocatalyst, optimized Pt₃Rh₁Ni₂-ANAs display remarkably enhanced EOR electrocatalytic performance in alkaline media.

The homogeneous incorporation of heteroatoms into two-dimensional C nanostructures, which leads to an increased chemical reactivity and electrical conductivity as well as enhanced synergistic catalysis as a conductive matrix to disperse and encapsulate active nanocatalysts, is highly attractive and quite challenging. In this study, by using the natural and cheap hydrotropic amino acid proline—which has remarkably high solubility in water and a desirable N content of ∼12.2 wt.%—as a C precursor pyrolyzed in the presence of a cubic KCl template, we developed a facile protocol for the large-scale production of N-doped C nanosheets with a hierarchically porous structure in a homogeneous dispersion. With concomitantly encapsulated and evenly spread Fe₂O₃ nano­particles surrounded by two protective ultrathin layers of inner Fe₃C and outer onion-like C, the resulting N-doped graphitic C nanosheet hybrids (Fe₂O₃@Fe₃C- NGCNs) exhibited a very high Li-storage capacity and excellent rate capability with a reliable and prolonged cycle life. A reversible capacity as high as 857 mAh⋅g^–1 at a current density of 100 mA⋅g^–1 was observed even after 100 cycles. The capacity retention at a current density 10 times higher—1, 000 mA⋅g^–1—reached 680 mAh⋅g^–1, which is 79% of that at 100 mA⋅g^–1, indicating that the hybrids are promising as anodes for advanced Li-ion batteries. The results highlight the importance of the heteroatomic dopant modification of the NGCNs host with tailored electronic and crystalline structures for competitive Li-storage features.

The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction (ORR) is extremely important for accelerating the commercial viability of direct methanol fuel cells (DMFCs). In this work, we present an efficient and template-free route for facile synthesis of cyanide (CN^-)-functionalized PtNi hollow nanospheres (PtNi@CN HNSs) with a high alloying degree using a simple cyanogel reduction method at room temperature. The physical and electrocatalytic properties of the PtNi@CN HNSs were investigated by various physical and electrochemical techniques. The PtNi@CN HNSs exhibited significantly enhanced electrocatalytic activity, durability, and particular methanol tolerance for the ORR as compared to commercial Pt black, and thus they are promising cathode electrocatalysts for DMFCs.

Catalysts for the oxygen reduction reaction (ORR) play an important role in fuel cells. Alternative non-precious metal catalysts with comparable ORR activity to Pt-based catalysts are highly desirable for the development of fuel cells. In this work, we report for the first time a spinel MnCo₂O₄/C ORR catalyst consisting of uniform MnCo₂O₄ nanoparticles cross-linked with two-dimensional (2D) porous carbon nanosheets (abbreviated as porous MnCo₂O₄/C nanosheets), in which glucose is used as the carbon source and NaCl as the template. The obtained porous MnCo₂O₄/C nanosheets present the combined properties of an interconnected porous architecture and a large surface area (175.3 m²·g^-1), as well as good electrical conductivity (1.15 × 10² S·cm^-1). Thus, the as-prepared MnCo₂O₄/C nanosheets efficiently facilitate electrolyte diffusion and offer an expedite transport path for reactants and electrons during the ORR. As a result, the as-prepared porous MnCo₂O₄/C nanosheet catalyst exhibits enhanced ORR activity with a higher onset potential and current density than those of its counterparts, including pure MnCo₂O₄, carbon nanosheets, and Vulcan XC-72R carbon. More importantly, the porous MnCo₂O₄/C nanosheets exhibit a comparable electrocatalytic activity but superior stability and tolerance toward methanol crossover effects than a high-performance Pt/C catalyst in alkaline medium. The synthetic strategy outlined here can be extended to other nonprecious metal catalysts for application in electrochemical energy conversion.