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As efficient nonprecious metal catalysts for oxygen reduction reaction (ORR), Fe-N-C materials are one of the most promising alternatives to Pt-based catalysts for fuel cells and metal-air batteries. However, the intrinsically low density of key active sites like FeN 4 moieties hampers their commercial applications. Herein, we provide a smart strategy to construct a candied haws-like Fe-N-C catalyst (CH-FeNC) with broadened carbon interplanar spacing (>4 Å), starting with trehalose as a structure-built brick coupled with a zinc-zeolite imidazole framework (ZIF-8) and polyaniline (PANI) and then followed by copyrolysis carbonization of them. The obtained CH-FeNC exhibits half-wave potentials of 0.92 and 0.90 V (vs RHE) before and after 10,000 cycles in 0.1 M KOH, which are superior to the 0.90 and 0.85 V obtained by commercial Pt/C for ORR. The power density of a homemade zinc-air battery equipped with the catalyst is up to 131 mW cm -2 , greater than that of Pt/C (124 mW cm -2 ). The extended X-ray absorption fine structure (EXAFS) results and density functional theory (DFT) theoretical calculations reveal that there exists enriched zigzag or armchair edge-hosted FeN 4 active sites, located at the abundant interface between carbon components in this composite. Furthermore, the unique broadened carbon interlayer spacing plays a key role in deciding the ORR rate in alkaline but not in acidic environments because there exists a fifth ligand of active Fe in the form of FeN 4 centers coupled with SO 4 2- and ClO 4 - from acids.

Few-atom metal clusters feature an extremely large surface area and abundant active sites, which are particularly important for electrocatalysis. Herein, we report a monoatomic cobalt tailoring strategy to boost the performance of platinum clusters (ca. <1 nm) via hetero-charge-trapping chemistry by ultraviolet light reducing Pt-based anions anchored on target Co cations. The created Co 1 Pt x clusters exhibit a mass activity of 2.27 A mg Pt -1 , which is about 1621% higher than that obtained by state-of-the-art Pt/C (2 nm) for the oxygen reduction reaction (ORR). This can be attributed to the butterfly effect of electron donor from monoatomic cobalt in the platinum clusters. Moreover, the improved stability results from the Co located at the bottom position of the Pt host, possessing high resistance to Co leaching. Therefore, this offers a general strategy to optimize the high performance of platinum group metal (PGM) clusters for electrocatalysis.

Strained platinum-based materials with high performance have been regarded as the most promising electrocatalysts for proton exchange membrane fuel cells (PEMFCs) recently. Herein, self-strained platinum clusters with finite size (about 1 nm) are prepared by a combining liquid- and solid-phase UV irradiation cycle strategy. It started with a fresh H 2 PtCl 6 solution irradiated by UV light and then mixed with a graphitized carbon, followed by the dried mixture being subjected to UV light to generate monodispersed Pt clusters on the carbon surface. The obtained platinum clusters feature narrower size distribution and higher loading on carbon, exhibiting significantly improved activity and durability, much higher than that of the-state-of-art commercial Pt/C for the oxygen reduction reaction. More importantly, the self-strained Pt clusters display a surprising CO tolerance, which can be attributed to the unique adaptive lattice compressive strain that triggers an electron enrichment phenomenon for the Pt clusters. Therefore, this stepwise UV irradiation method solves the long-standing problem of both wide size distribution and low loading of metal clusters fabricated by one-step photochemical reduction, providing a potential route for the synthesis of other metal clusters with strained structures.

Plant-derived nonprecious metal catalysts are considered one of the promising candidates of platinum for oxygen reduction reaction (ORR). In this work, the typical microscopic morphology of fresh green crop yam is first detected by cryoscanning electronic microscopy. Using the green and widely sourced yam with spherical starch in nature as a precursor, well-defined spherical carbons are prepared via hypersaline-assisted hydrothermal carbonization and NH 3 activation, featuring a high heteroatom doping level and a hierarchical porous structure. Experimental results and density functional theory (DFT) calculations reveal that diverse off-plane Fe-N x -C y ensembles on the spherical carbons trigger the high performance that exceeds state-of-art Pt/C and most reported carbon catalysts toward ORR in a KOH solution. The increased charge density and the bond length of Fe coordinated in the sites should be responsible for the significantly improved property. The easily editing of off-plane active sites from the simple carbon morphology may shed light on optimizing nonprecious carbons as next-generation catalysts for ORR.

Integrating crystal orientation as well as structural and compositional advantages into one catalyst might be a promising strategy for high-performance Pt-based catalysts for proton-exchange membrane fuel cells. Herein, by introducing W(CO) 6 as a structure-oriented template, Pt-based alloys with a well-defined crystal orientation along the (111) facet were obtained. The oxygen reduction reaction mass and specific activities of the crystal-facet-tuned alloys reach a new level. Moreover, the outstanding durability stems from the combination of their exposed crystal facets and incorporated W. The density functional theory calculation results reveal that the formation of the preferred (111) alloys can be attributed to the lower free energy of (111) facets and the weaker adsorption of CO released by W(CO) 6 . This proposed synthesis strategy of using transition-metal carbonyl compounds as additives to synthesize alloys with strong crystal orientation may open a door to the design of various alloy catalysts with ultrahigh activity.

The unaffordable costs of the automotive proton exchange membrane fuel cell (PEMFC), remaining a roadblock for commercial applications as an alternative to combustion engine vehicles, can be overcome partially by remarkably increasing the utilization of irreplaceable platinum (Pt). Herein, atomically precise Pt with scalable atoms ranging from 1 to 43 atoms, stabilized by a homemade carbon from white radish without any ligands, is prepared by a repeated UV irradiation method that is industrially scalable. Compared with the isolated Pt 1 in the form of Pt-N 4 , octahedral Pt 6 , and icosahedron Pt 13 , the ordered Pt 43 cluster (∼0.75 nm) with higher metal coordination number displays much higher oxygen reduction reaction performance with a mass activity, which is about 1036% higher than that obtained by state-of-the-art Pt/C, an increase by a factor of ∼3.3 as compared with the DOE 2020 target (0.44 A mg Pt -1 ). The utilization rate of Pt atoms reaches up to 94.7%, much higher than that of Pt (2 nm, 56%), capable of further reducing the amount of platinum that is required for PEMFCs. Moreover, the cluster exhibits an outstanding stability due to the improved Pt vacancy formation energy raised by stronger atom interaction in the close-packed cluster. The cluster exhibits a unique finite size effect from self-tuned energy band and strain levels. A clear strain effect on the d-band center is first presented for pure Pt without distortion from ligands like a second metal. Therefore, the assembly of subnanometer Pt with atom alteration opens up new horizons in designing efficient platinum group metal (PGM) catalysts by reducing the size to subnanometer scale.

In this work, platinum single-atom enhanced mushroom-based carbon (Pt 1 /MC) materials have been facilely synthesized and served as novel electrode materials in lithium-ion batteries (LIBs). The as-synthesized Pt 1 /MC active material shows a uniform dispersion of isolated Pt atoms on an MC support with high specific surface area and large total pore volume. As a negative electrode material for LIBs, the Pt 1 /MC exhibits excellent electrochemical properties, which retains a capacity of 846 mA h g -1 after 800 cycles at 2 A g -1 and 349 mA h g -1 (near to the theoretical capacity of graphite) after 6000 cycles at a high current density of 5 A g -1 . The remarkable high capacity and excellent cycling stability can be attributed to their porous nanostructures and atomic-Pt-enhanced lithium-ion storage. Atomic Pt can compound with Li + ions to form a platinum-lithium alloy during the discharge and charge process. Density functional theory (DFT) calculations are performed to verify that the PtLi 5 alloy is the most stable intermedium on the MC substrate, which further enhances the lithiation and delithiation kinetics. This novel perspective is helpful to explore next-generation negative electrode materials with high capacities and good stabilities for LIBs.

Controllable pyrolysis of collapsible metal-organic frameworks (MOFs) into carbon-based nanostructures without obvious collapse and aggregation is of importance for the fabrication of well catalytic active and durable carbon-based catalysts for the oxygen reduction reaction (ORR). Herein, we fabricate morphology-controlled carbon-based nanostructures derived from the Co-based zeolitic imidazolate framework (ZIF-67) that epitaxially grows on layered lanthanum oxycarbonate (La 2 O 2 CO 3 ) as a structure-oriented template, followed by pyrolysis at 800 °C. These synthesized carbon-based nanostructures show a well-defined dodecahedron morphology and vertical array on the template surface. In 0.1 M KOH solution, the ORR activity and durability of the carbon-based nanostructures are not only much higher than those obtained by pyrolytic carbons derived from pure ZIF-67 but also exceed commercial Pt/C (20 wt %, Pt). The significantly improved ORR performance can be ascribed to the increased Co-N x level, high specific surface area, and graphitization of the pyrolytic carbon, caused by the introduction of the La 2 O 2 CO 3 phase into the composite catalyst. Therefore, using La 2 O 2 CO 3 as the template may be a smart synthetic strategy for MOF-derived nanocarbons with a controlled morphology and composition for energy storages and conversions.

Developing atomic-level transition oxides may be one of the most promising ways for providing ultrahigh electrocatalytic performance for oxygen reduction reaction (ORR), compared with their bulk counterparts. In this article, we developed a set of atomically thick Co 3 O 4 layers covered on Co nanoparticles through partial reduction of Co 3 O 4 nanoparticles using melamine as a reductive additive at an elevated temperature. Compared with the original Co 3 O 4 nanoparticles, the synthesized Co 3 O 4 with a thickness of 1.1 nm exhibits remarkably enhanced ORR activity and durability, which are even higher than those obtained by a commercial Pt/C in an alkaline environment. The superior activity can be attributed to the unique physical and chemical structures of the atomic-level oxide featuring the narrowed band gap and decreased work function, caused by the escaped lattice oxygen and the enriched coordination-unsaturated Co 2+ in this atomic layer. Besides, the outstanding durability of the catalyst can result from the chemically epitaxial deposition of the Co 3 O 4 on the cobalt surface. Therefore, the proposed synthetic strategy may offer a smart way to develop other atomic-level transition metals with high electrocatalytic activity and stability for energy conversion and storage devices.

Lattice contraction has been regarded as an important factor influencing oxygen reduction reaction (ORR) activity of Pt-based alloys. However, the relationship between quantitative lattice contraction and ORR activity has rarely been reported. Herein, using Pt-Cu alloy nanoparticles (NPs) with similar particle sizes but different compositions as examples, we investigated the relationship between quantitative lattice contraction and ORR activity by defining the shrinking percentage of Pt-Pt bond distance as lattice contraction percentage. The results show that the ORR activities of Pt-Cu alloy NPs exhibit a well-defined volcano-type dependent relationship toward the lattice contraction percentage. The dependent correlation can be explained by the Sabatier principle. This study not only proposes a valid descriptor to bridge the activity and atomic composition but also provides a reference for understanding the composition-structure-activity relationship of Pt-based alloys.

Constructing nanoscale hybrid materials with unique interfacial structures by using various metal oxides and carbon supports as building blocks are of great importance to develop highly active, economical hybrid catalysts for oxygen reduction reaction (ORR). In this work, La2O2CO3 encapsulated La2O3 nanoparticles on a carbon black (La2O2CO3@La2O3/C) were fabricated via chemical precipitation in an aqueous solution containing different concentrations of cetyltrimethyl ammonium bromide (CTAB), followed by calcination at 750 °C. At a given CTAB concentration 24.8 mmol/L, the obtained lanthanum compound nanoparticles reach the smallest particle size (7.1 nm) and are well-dispersed on the carbon surface. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate the formation of La2O2CO3 located on the surface of La2O3 nanoparticles in the hybrid. The synthesized La2O2CO3@La2O3/C hybrid exhibits a significantly enhanced electrocatalytic activity in electrocatalysis experiments relative to pure La2O3, La2O2CO3, and carbon in an alkaline environment, by using the R(R)DE technique. Moreover, its long-term stability also outperforms that obtained by commercial Pt/C catalysts (E-TEK). The exact origin of the fast ORR kinetics is mainly ascribed to the La2O2CO3 layer sandwiched at the interface of carbon and La2O3, which contributes favorable surface-adsorbed hydroxide (-OH(-)(ad)) substitution and promotes active oxygen adsorption at the interfaces. The unique covalent -C-O-C(═O)-O-La-O- bonds, formed at the interfaces between La2O2CO3 and carbon, can act as active sites for the improved ORR kinetics over this hybrid catalyst. Therefore, the fabrication of lanthanum compound-based hybrid material with an unique interfacial structure maybe open a new way to develop carbon-supported metal oxides as next-generation of ORR catalysts.

Surface-functionalized multiwalled carbon nanotubes (MWCNTs) supported Pd100-xIrx binary alloy nanoparticles (Pd100-xIrx/MWCNT) with tunable Pd/Ir atomic ratios were synthesized by a thermolytic process at varied ratios of bis(acetylacetonate) palladium(II) and iridium(III) 2,4-pentanedionate precursors and then applied as the electrocatalyst for the formic acid electro-oxidation. The X-ray diffraction pattern (XRD) and transmission electron microscope (TEM) analysis showed that the Pd100-xIrx alloy nanoparticles with the average size of 6.2 nm were uniformly dispersed on the MWCNTs and exhibited a single solid solution phase with a face-centered cubic structure. The electrocatalytic properties were evaluated through the cyclic voltammetry and chronoamperometry tests, and the results indicated that both the activity and stability of Pd100-xIrx/MWCNT were strongly dependent on the Pd/Ir atomic ratios: the best electrocatalytic performance in terms of onset potential, current density, and stability against CO poisoning was obtained for the Pd79Ir21/MWCNT. Moreover, compared with pure Pd nanoparticles supported on MWCNTs (Pd/MWCNT), the Pd79Ir21/MWCNT exhibited enhanced steady-state current density and higher stability, as well as maintained excellent electrocatalytic activity in high concentrated formic acid solution, which was attributed to the bifunctional effect through alloying Pd with transition metal.