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Proton-exchange membrane fuel cells (PEMFCs) are limited by their extreme sensitivity to trace-level CO impurities, thus setting a strict requirement for H2 purity and excluding the possibility to directly use cheap crude hydrogen as fuel. Herein, we report a proof-of-concept study, in which a novel catalyst comprising both Ir particles and Ir single-atom sites (IrNP @IrSA -N-C) addresses the CO poisoning issue. The Ir single-atom sites are found not only to be good CO oxidizing sites, but also excel in scavenging the CO molecules adsorbed on Ir particles in close proximity, thereby enabling the Ir particles to reserve partial active sites towards H2 oxidation. The interplay between Ir nanoparticles and Ir single-atom centers confers the catalyst with both excellent H2 oxidation activity (1.19 W cm-2 ) and excellent CO electro-oxidation activity (85 mW cm-2 ) in PEMFCs; the catalyst also tolerates CO in H2 /CO mixture gas at a level that is two times better than that of the current best PtRu/C catalyst.

Electrochemical production of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (ORR) process is emerging as a promising alternative method to the conventional anthraquinone process. To realize high-efficiency H2O2 electrosynthesis, robust and low cost electrocatalysts have been intensively pursued, among which Co-based catalysts attract particular research interests due to the earth-abundance and high selectivity. Here, we provide a comprehensive review on the advancement of Co-based electrocatalyst for H2O2 electroproduction. The fundamental chemistry of 2-electron ORR is discussed firstly for guiding the rational design of electrocatalysts. Subsequently, the development of Co-based electrocatalysts involving nanoparticles, compounds and single atom catalysts is summarized with the focus on active site identification, structure regulation and mechanism understanding. Moreover, the current challenges and future directions of the Co-based electrocatalysts are briefly summarized in this review.

In this study, phosphorus doped graphene supported PtNiP nanocluster electrocatalyst (PtNiP/P-graphene) was successfully prepared via a simple hypophosphite-assisted co-reduction method. The improved anchoring force and increased anchoring sites of graphene support result from phosphorus doping as well as size-confined growth effect of NaH2PO2 leads to uniform dispersion of ultrafine PtNiP nanoclusters. Doped P also promotes the removal of CO-like intermediate by adjusting Pt electronic structure combining with alloyed Ni via electronic effects. As a result, the as-prepared PtNiP/P-graphene catalyst with more exposed active sites and optimized electronic structure of Pt alloy shows excellent electrocatalytic performances for methanol oxidation reaction (MOR) both in activity and durability in an acidic medium.

Highly active and durable electrocatalysts with minimal Pt usage are desired for commercial fuel cell applications. Herein, we present a highly dispersed L10-PtZn intermetallic catalyst for the oxygen reduction reaction (ORR), in which a Zn-rich metal-organic framework (MOF) is used as an in situ generated support to confine the growth of PtZn particles. Despite requiring high-temperature treatment, the intermetallic L10-PtZn particles exhibit a small mean size of 3.95 nm, which confers the catalysts with high electrochemical active surface area (81.9 m2 gPt−1) and atomic utilization. The Pt electron structure and binding strength between Pt and oxygen intermediates are optimized through ligand effect and compressive strain. These advantages result in ORR mass activity and specific activity of 0.926 A mgPt−1 and 1.13 mA cm−2, respectively, which are 5.4 and 4.0 times those of commercial Pt/C. The stable L10 structure provides the catalysts with superb durability; only a halfwave potential loss of 11 mV is observed after 30,000 cycles of accelerated stress tests, through which the structure evolves into a more stable PtZn-Pt core-shell structure. Therefore, the development of a Zn based MOF as a catalyst support is demonstrated, providing a synergy strategy to prepare highly dispersed intermetallic alloys with high activity and durability.

Metal-nitrogen-carbon materials (M-N-C) are non-noble-metal-based alternatives to platinum-based catalysts and have attracted tremendous attention due to their low-cost, high abundance, and efficient catalytic performance towards the oxygen reduction reaction (ORR). Among them, Fe-based materials show remarkable ORR activity, but they are limited by low selectivity and low stability. To address these issues, herein, we have synthesized FeCu-based M-N-C catalysts, inspired by the bimetal center of cytochrome c oxidase (CcO). In acidic media, the selectivity was notably improved compared with Fe-based materials, with peroxide yields less than 1.2% (

Fuel cells, a sustainable technology that assures a cleaner earth, once experienced disillusion due to the issue of economic viability associated with the massive usage of Pt-based catalysts. To address this issue, research on cost-effective catalysts, especially on the cathode side, has been intensively carried out where the latest achievements have made the M–Nx/C material on its verge of application. Here, we present a comprehensive overview of the fundamental chemistry of oxygen reduction reaction (ORR) and the progress of the M–Nx/C catalysts. Efforts aimed at clarifying the nature of catalytic sites are summarized, highlighting the indispensable role of advanced characterization tools. A variety of successful attempts are exemplified to describe the synthetic methodologies, followed by close tracking of newly emerging single-atom or dual-atom sites. Future directions for this research area are believed to be the rational and/or controllable synthesis of catalysts with adequate active sites and the use of strategies to substantially alleviate catalyst degradation.

The local electronic configuration of active sites in molybdenum disulfide (MoS2) could significantly alter the intrinsic activity towards hydrogen evolution reaction (HER). Herein, we report that the HER performance of MoS2 electrocatalysts was boosted via bismuth and palladium co-doping. The introduction of heteroatom Bi successfully altered the local electronic configuration of S atoms in the MoS2 inert basal plane to form an electron-enriched environment, conducive to boost active site density and proton adsorption, as experimentally verified by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Furthermore, after activating the MoS2 via Pd doping, a phase transition to stable 1 T phase occurred which was verified by Raman. In acidic media, the as-prepared Bi/Pd-MoS2 catalyst exhibited excellent electrochemical HER performance in terms of a low overpotential of -114 mV at a current density of 10 mA cm−2, a small Tafel slope of 65 mV dec−1, and outstanding long-term stability.

Lowering the Pt catalyst loading in fuel cell cathodes without sacrificing performance remains a topic of interest. However, achieving such a goal is highly challenging, because lowering the Pt loa...

Formic acid dehydrogenation (FAD) offers an ideal route for hydrogen production, where searching for efficient and selective catalysts is imperative. However, the current state-of-the-art Pd-based metallic catalysts severely suffer from low catalytic efficiency and self-poisoning, owning to the FA dehydration side reaction. In this work, we design PANI-Pd/C composite catalysts via interfacial microenvironment regulation technique. The as-prepared 0.01-PANI-Pd/C catalyst exhibits high turnover frequency (TOF, 5654 h−1) and excellent resistance to CO poisoning. The merit of polyaniline can be ascribed to: a) construction of abundant Pd–PdO interfaces; b) capturing H+ and accelerating the formation of the reactive species.

The applications of the most promising Fe-N-C catalysts are prohibited by their limited intrinsic activities. Manipulating the Fe energy level through anchoring electron-withdrawing ligands is found effective in boosting the catalytic performance. However, such regulation remains elusive as the ligands are only uncontrollably introduced oweing to their energetically unstable nature. Herein, we report a rational manipulation strategy for introducing axial bonded O to the Fe sites, attained through hexa-coordinating Fe with oxygen functional groups in the precursor. Moreover, the O modifier is stabilized by forming the Fe-O-Fe bridge bond, with the approximation of two FeN4 sites. The energy level modulation thus created confers the sites with an intrinsic activity that is over 10 times higher than that of the normal FeN4 site. Our finding opens a novel strategy to manage coordination environments at an atomic level for high activity ORR catalysts.

Fe/N/C material is the most competitive alternative to precious-metal catalysts for oxygen reduction. In view of the present consensus on active centers, further effort is directed at maximizing the density of single Fe atoms. Here, the imperfections in commonly used doping strategy of Fe for the synthesis of zeolitic imidazolateframework (ZIF)-derived Fe/N/C catalysts are revealed. More importantly, a strikingly improved catalyst is obtained by a ‘second pyrolysis’ method and delivers a half-wave potential of 0.825 V (vs. RHE) in acidic media. The strong confinement effect of carbonaceous host accounts for the formation of dense single-atom sites and thus the high activity. Our findings will potentially facilitate future improvement of M/N/C catalysts.

Engineering the reaction interface to preferentially attract reactants to inner Helmholtz plane is highly desirable for kinetic advancement of most electro-catalysis processes, including hydrogen evolution reaction (HER). This, however, has rarely been achieved due to the inherent complexity for precise surface manipulation down to molecule level. Here, we build a MoS2 di-anionic surface with controlled molecular substitution of S sites by –OH. We confirm the –OH group endows the interface with reactant dragging functionality, through forming strong non-covalent hydrogen bonding to the reactants (hydronium ions or water). The well-conditioned surface, in conjunction with activated sulfur atoms (by heteroatom metal doping) as active sites, giving rise to up-to-date the lowest over potential and highest intrinsic activity among all the MoS2 based catalysts. The di-anion surface created in this study, with atomic mixing of active sites and reactant dragging functionalities, represents a effective di-functional interface for boosted kinetic performance. H2 energy as an alternative to fossil fuels requires cost-effective catalysts with fast kinetics for splitting water. Here, authors design MoS2 materials with di-anionic surfaces to improve the electrocatalytic H2 evolution activities.

Supported metals are widely used as industrial catalysts wherein the supports affect catalytic performances remarkably through either electronic and/or geometric interactions with the metals, and/or providing interfacial synergistic sites. Herein, we observed evidence for interfacial geometric interactions (IGIs) at Pt–C interfaces through a combination of atomic-scale structural analysis, in situ X-ray absorption fine structure, and electrochemical measurements for Pt/C model systems. The IGI has a long-range attribute and affects Pt surface atoms not only at interfacial perimeters but also adjacent to interfaces. The affected Pt surface atoms are proposed to contribute enhanced activity and stability for the oxygen reduction reaction through retarding the formation of strongly adsorbed oxygenated intermediates. Our work provides some necessary information for a better understanding of support effects and catalytically active surface sites.

Hydrogen production from formic acid decomposition (FAD) is a promising means of hydrogen energy storage and utilization in fuel cells. Development of efficient catalysts for dehydrogenation of formic acid is a challenging topic. The surface chemical and electronic structure of the active catalysis components is important in formic acid decomposition at room-temperature. Here, the pyrdinic-nitrogen doped catalysts from hyperbranched polyamide were prepared via in situ polymerization reaction process by using activated carbon as a support. Because of the introduction of the polymer, the particles of the catalysts were stabilized, and the average particle diameter was only 1.64 nm. Under mild conditions, the catalysts activities were evaluated for FAD. The optimized Pd-N30/C catalyst exhibited high performance achieving almost full conversion, with a turnover frequency of 3481 h−1 at 30 °C.

Significance We report a class of IrRu-N-C catalysts, with Ir and Ru single atoms uniformly populated in nitrogen–carbon composites. The catalyst not only represents an example of high-efficiency single-atom catalysis toward H 2 electrooxidation, but also exhibits excellent CO electrooxidation reaction (COOR) behavior. The traditionally invincible CO electrooxidation process occurs easily on this catalyst, with COOR initiates at nearly 0 mV versus reversible hydrogen electrode at ambient temperature. This endows the catalyst with superb CO antipoisoning property in proton exchange membrane fuel cell at ultralow noble metal loading. Combining theoretical calculation and physical probing techniques, we find that the approximated Ir and Ru single atomic sites act in synergy to confer the catalysts with this excellent CO conversion behavior.

Well-dispersed palladium nanoparticles (NPs) anchored on a porous N-doped carbon is prepared by wet chemical method, using metal organic frameworks (ZIF-8) as a precursor to derive the porous N-doped carbon support. Benefitting from the N-doping and the porous structure of the carbon materials, the final Pd NPs are in high dispersion and exhibit reduced particle sizes, with electronic structure and chemical status tuned to favor the formic acid decomposition (FAD). The prepared Pd/CZIF-8-950 catalysts show enhanced catalytic performance and selectivity for FAD, the turnover of frequency (TOF) and the mass activity up to 1166 h−1 and 11.01 mol H2 g−1 pd h−1 were obtained at 30 °C. This work provides an effective and easy way for synthesis the Pd-based catalyst, which has enormous application prospects for the next generation hydrogen energy preparation and storage.

The catalytic activity of 2H-MoS2 is retarded by the deficiency in active sites, inferior intrinsic activity, and slow electron transfer kinetics. However, the strategies to concurrently resolve th...

Single-atom catalysts (SACs) are attracting widespread interest for the catalytic oxygen reduction reaction (ORR), with Fe-Nx SACs exhibiting the most promising activity. However, Fe-based catalysts suffer serious stability issues as a result of oxidative corrosion through the Fenton reaction. Herein, using a metal-organic framework as an anchoring matrix, we for the first time obtained pyrolyzed Cr/N/C SACs for the ORR, where the atomically dispersed Cr is confirmed to have a Cr-N4 coordination structure. The Cr/N/C catalyst exhibits excellent ORR activity with an optimal half-wave potential of 0.773 V versus RHE. More excitingly, the Fenton reaction is substantially reduced and, thus, the final catalysts show superb stability. The innovative and robust active site for the ORR opens a new possibility to circumvent the stability issue of the non-noble metal ORR catalysts.

Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts. The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield (1%) and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.

Transition metal and nitrogen co-doped carbon (M–N/C) catalysts are recognized as the most prospective alternatives for platinum-based electro-catalysts towards oxygen reduction reaction (ORR) in polymer electrolyte fuel cells. Recently, significant progress has been achieved in the identification and regulation of active sites of this kind of catalysts. In this mini review, we summarize the techniques and strategies to identify active sites in M–N/C catalysts, the main debates on active sites types, the measurement method for active site density, the reactivity descriptors for M–N/C catalysts, and directions to the design of ORR M–N/C catalysts.

The electrochemical methanol oxidation reaction (MOR) is of paramount importance for direct methanol fuel cell (DMFC) application, where efficient catalysts are required to facilitate the complicated multiple charge transfer process. The catalyst support not only determines the dispersion status of the catalysts particles, but also exerts great influence on the electronic structure of the catalysts, thereby altering its intrinsic activity. Herein, we demonstrated that nitrogen atoms, assisted by the pre-treatment of carbon matrix with oxidants, can be easily doped into carbon nanotubes at low temperature. The obtained nitrogen-doped carbon nanotubes can effectively improve the dispersion of the supported platinum nanoparticles and facilitate the MOR by modifying the electronic structure of platinum atoms, through catalyst-support interaction.

Engineering an electrocatalytic anode material to boost reaction kinetics is highly desirable for the anodic oxygen evolution reaction (OER), which is the major obstacle for high efficiency water electrolysis. Here, we present a novel kind of Zn-doped Co3O4 hollow dodecahedral electrocatalyst. Abundant oxygen vacancy defects are introduced due to the incorporation of Zn2+, which is beneficial for OH− adsorption and the charge transfer reaction during the OER process. Moreover, the increase in surface area caused by the advanced structure of the hollow porous dodecahedra facilitates mass transport by increasing the surface area. The novel strategy proposed in this study provides an efficient way to design high-performance electrocatalysts for water electrolysis. A cheap catalyst that aids water splitting and is made from readily available materials has been developed by researchers in China. Hydrogen releases energy when burned in air, and is therefore a promising source of clean power. Hydrogen can be sourced by splitting water into its constituent atoms, but the chemical reaction separating hydrogen and oxygen, known as the oxygen evolution reaction, is not particularly efficient. Yao Xiao and coworkers from the Changchun Institute of Applied Chemistry developed an oxygen evolution reaction electrocatalyst made from zinc-doped cobalt oxide, Zn-Co3O4. The catalyst has a unique dodecahedral structure, and the team believes it is its large surface area that is responsible for its excellent performance. Unlike many other water-splitting catalysts, the constituent materials of Zn-Co3O4 are cheap and readily available. Cobaltosic oxide hollow dodecahedra with abundant oxygen vacancy defects was synthesized and manifested extraordinary catalytic performance toward the oxygen evolution reaction.

Pyrolytic transition metal nitrogen-carbon (M-N/C) materials are considered as the most promising alternatives for platinum-based catalysts toward oxygen reduction reaction (ORR). As the proton-coupled electron transfer step in ORR has been proven to be a rate-determining step in the M-N/C catalysts, we envisaged that building a protophilic surface might be helpful to enhance the ORR activity. Herein, a polyaniline decoration strategy was put forward and realized to confer the Fe-N/C catalyst with a surface protophilic environment. A 20 mV positive shift in half-wave potential was observed owing to the enriched interfacial proton concentration, corresponding to a tripled turnover frequency under acidic conditions (from 0.46 to 1.28 e·s-1·sites-1). Our work blazed a new path toward the design of M-N/C ORR catalysts, commencing via the ORR kinetics.

The oxygen evolution reaction (OER), as the anodic reaction of water electrolysis (WE), suffers greatly from low reaction kinetics and thereby hampers the large-scale application of WE. Seeking active, stable, and cost-effective OER catalysts in acidic media is therefore of great significance. In this perspective, studying the reaction mechanism and exploiting advanced anode catalysts are of equal importance, where the former provides guidance for material structural engineering towards a better catalytic activity. In this review, we first summarize the currently proposed OER catalytic mechanisms, i.e., the adsorbate evolution mechanism (AEM) and lattice oxygen evolution reaction (LOER). Subsequently, we critically review several acidic OER electrocatalysts reported recently, with focus on structure–performance correlation. Finally, a few suggestions on exploring future OER catalysts are proposed.

Formic acid decomposition (FAD) is one of the most promising routes for rapid hydrogen (H2) production. Extensive efforts have been taken to develop efficient catalysts, which calls for the simultaneous regulation of the electronic structure and particle size of the catalyst. The former factor determines the intrinsic performance, while the latter corresponds to the active site utilization. Here, an effective preparation strategy, pre-nucleation coupled with in situ reduction, is developed to realize and well-tune both surface electronic states and particle size of the pallidum (Pd) catalyst. Benefiting from the structural merits, the as-prepared catalyst exhibits high mass-specific activity of 8.94 molH2/(gPd·h) with few carbon monoxide (CO) molecules, and the activation energy could reach a value as small as 33.1 kJ/mol. The work not only affords a highly competitive FAD catalyst but also paves a new avenue to the synthesis of ultra-fine metal nanoparticles with tailorable electronic structures.

Reducing the cost of Pt-base ORR electrocatalysts is highly desirable for fuel-cell commercialization. One of the effective strategies is increasing Pt utilization by forming structures with accessible surface. Another is increasing intrinsic activity of Pt sites by redesigning electronic structure. Here, we developed a hollow Pt sphere with a compressive Pt surface on carbonized resorcinol–formaldehyde resin. The special hollow structure with accessible channel endows the nanoparticles with high Pt atom utilization. And the compressive Pt-rich shell gives rise to the enhanced intrinsic activity via tuning Pt d-band electronic structure. As a result, the PtFe(0.9)-C catalysts with an ultralow Pt loading of 0.86% achieved a 2.3 and 2.7 times enhancement in mass activity and specific activity relative to state-of-the-art Pt/C-20% catalysts.

Pyrolyzed Fe-NX/C materials derived from Fe-doped ZIF-8 are recently emerged as promising alternatives to noble metal platinum-based catalysts towards oxygen reduction reaction (ORR) and elucidating the dependacne of Fe source on the active site structure and final ORR performance is highly desirbale for further development of these materials. Here, we designed and synthesized a series of Fe-N-C catalysts using ZIF-8 and various iron salts (Fe(acac)3, FeCl3, Fe(NO3)3) as precusors. We found that the iron precursors, mainly the molecular size, hydrolysis extent, do play a major role in determining the final morphology of Fe, namely forming the Fe-Nx coordination or Fe3C nanoparticles, as well as the site density, therefore, significantly affecting the ORR activity. Among the three iron sources, Fe(acac)3 is most advantageous to the preferential formation of single-atom Fe-Nx active sites and the derived catalyst demonstrated best ORR performance.

Direct methanol fuel cells (DMFCs) are very promising power source for stationary and portable miniature electric appliances due to its high efficiency and low emissions of pollutants. As the key material, catalysts for both cathode and anode face several problems which hinder the commercialization of DMFCs. In this review, we mainly focus on anode catalysts of DMFCs. The process and mechanism of methanol electrooxidation on Pt and Pt-based catalysts in acidic medium have been introduced. The influences of size effect and morphology on electrocatalytic activity are discussed though whether there is a size effect in MOR catalyst is under debate. Besides, the non Pt catalysts are also listed to emphasize though Pt is still deemed as the indispensable element in anode catalyst of DMFCs in acidic medium. Different catalyst systems are compared to illustrate the level of research at present. Some debates need to be verified with experimental evidences.

Reducing the noble-metal loading without sacrificing the catalytic performance of the oxygen evolution reaction (OER) catalysts is paramount yet highly challenging. Herein, IrO2@Ir/TiN electrocatalysts employing TiN as the support have been developed and shown high efficiency toward OER. TiN is found not only to disperse the IrO2@Ir nanoparticles effectively but also to exert the electronic modulation of Ir by downshifting its d-band center of 0.21 eV compared to pure IrO2. Excitingly, TiN remarkably enhances the catalytic performance of Ir, where the overpotential to achieve the current density of 10 mA cm-2 is only 265 mV for the IrO2@Ir/TiN (60 wt %) catalyst. As a result, 71.7 wt % of the Ir metal can be saved to compare with the commercial Ir-black counterpart. Moreover, TiN can inhibit the aggregation and oxidative dissolution of Ir species, thereby enhancing the operational stability. The combined advantages of TiN open a new solution to reduce the anodic catalyst cost through boosting the catalytic activity and stability.

Searching for cost-efficient electrocatalysts with high catalytic activity and stability for hydrogen generation by means of water electrolysis would make a great improvement on energy technologies field. Herein, we report high-performance hydrogen evolution reaction (HER) electrocatalysts based on sulfur-doped Ni

Metal-free electrocatalysts have eluded widespread adoption in polymer electrolyte membrane fuel cells due to their far inferior catalytic activity than most non-precious metal-N-C counterparts (M-Nx-C) for oxygen reduction reaction (ORR), despite their distinct advantages over the M-Nx-C catalysts, including lower cost and higher durability. Herein, we develop a rational bottom-up engineering strategy to improve the ORR performance of a metal-free catalyst by constructing a three-dimensional ultrathin N, P dual-doped carbon nanosheet. The resultant catalyst represents unprecedented ORR performance with an onset potential of 0.91 V, half-wave potential of 0.79 V. Impressively, a maximum power output at 579 mW cm−2 is generated in the fuel cell test, the best among reported metal-free catalysts and outperforms most of the M-Nx-C catalysts. The outstanding catalytic performance results from the highly active polarized carbon sites which are induced by selective graphitic nitrogen and phosphorous dual doping. Our findings provide new directions for the exploration of alternatives to Pt and bring a renew interests in the metal-free catalysts.

Lacking strategies to simultaneously address the intrinsic activity, site density, electrical transport, and stability problems of chalcogels is restricting their application in catalytic hydrogen production. Herein, we resolve these challenges concurrently through chemically activating the molybdenum disulfide (MoS2) surface basal plane by doping with a low content of atomic palladium using a spontaneous interfacial redox technique. Palladium substitution occurs at the molybdenum site, simultaneously introducing sulfur vacancy and converting the 2H into the stabilized 1T structure. Theoretical calculations demonstrate the sulfur atoms next to the palladium sites exhibit low hydrogen adsorption energy at –0.02 eV. The final MoS2 doped with only 1wt% of palladium demonstrates exchange current density of 805 μA cm−2 and 78 mV overpotential at 10 mA cm−2, accompanied by a good stability. The combined advantages of our surface activating technique open the possibility of manipulating the catalytic performance of MoS2 to rival platinum. While water reduction may provide a carbon-neutral means to produce hydrogen gas, there is a scarcity of efficient, earth-abundant electrocatalysts. Here, the authors add palladium into MoS2 materials to activate and stabilize the conductive basal plane to improve the electrocatalytic activity.

Formic acid, as the simplest carboxylic acid which can be obtained as an industrial by-product, is colorless, low toxicity, and easy to transport and storage at room temperature. Recently, Formic acid has aroused wide-spread interest as a promising material for hydrogen storage. Compared to other organic small molecules, the temperature for formic acid decomposition to produce hydrogen is lower, resulting in less CO toxicant species. Lots of catalysts on both homogeneous catalysts and heterogeneous were reported for the decomposition of formic acid to yield hydrogen and carbon dioxide at mild condition. In this paper, the recent development of mechanism and the material study for both homogeneous catalysts and heterogeneous catalysts are reviewed in detail.

Herein, a novel binuclear active site structure, Co2NxCy, is intentionally designed and successfully fabricated to efficiently catalyze the oxygen reduction reaction (ORR), which is achieved by precisely controlling the atomic scale structure of bimetal-organic frameworks before pyrolysis. Through discovering a two-atom site with Co-Co distance at 2.1–2.2 A from aberration-corrected scanning transmission electron microscopy (STEM), as well as a novel shortened Co-Co path (2.12 A) from the X-ray absorption spectroscopy, we for the first time identified the binuclear Co2NX site in the pyrolyzed catalyst. Combined with density functional theory (DFT) calculation, the structure is further confirmed as Co2N5. Excitingly, the Co2N5 site performs approximately 12 times higher activity than the conventional CoN4 site and the corresponding catalyst shows unprecedented catalytic activity in acidic electrolyte with half-wave potential of 0.79 V, approaching the commercial Pt/C catalyst and presenting the best one among the Co-N-C catalysts. Theoretical density functional theory calculations reveal that the novel binuclear site exhibits considerably reduced thermodynamic barrier towards ORR, thus contributing to the much higher intrinsic activity. Our finding opens up a new path to design efficient M-Nx/C catalysts, thus pushing the fuel cell industry field one step ahead.

Developing highly efficient, low-cost oxygen reduction catalysts, especially in acidic medium, is of significance toward fuel cell commercialization. Although pyrolyzed Fe-N-C catalysts have been regarded as alternatives to platinum-based catalytic materials, further improvement requires precise control of the Fe-Nx structure at the molecular level and a comprehensive understanding of catalytic site structure and the ORR mechanism on these materials. In this report, we present a microporous metal–organic-framework-confined strategy toward the preferable formation of single-atom dispersed catalysts. The onset potential for Fe-N-C is 0.92 V, comparable to that of Pt/C and outperforming most noble-metal-free catalysts ever reported. A high-spin Fe3+-N4 configuration is revealed by the 57Fe Mossbauer spectrum and X-ray absorption spectroscopy for Fe L-edge, which will convert to Fe2+-N4 at low potential. The in situ reduced Fe2+-N4 moiety from high-spin Ox-Fe3+-N4 contributes to most of the ORR activity due t...

Splitting HCOOH (FA) into H2 and CO2 with high turnover frequencies and selectivity is highly desirable for H2 generation and its facilitated utilization. However, the mostly adopted Pd based metallic catalysts are severely suffered from low catalytic efficiency and self-poisoning, owning to the FA dehydration side reaction. Here, we demonstrate firstly that the secret for developing high active and selective Pd towards FAD lies in building abundant Pd-PdO interface at the catalytic surface. Using chemical blocking technique, we identify surface Pd (0) as the active sites for FA adsorption. By combining the density functional theoretical calculations, experiments, and in situ sensitive probes, PdO is found active in fastening the dehydrogenation rate through pulling hydrogen from the reaction intermediates, as well as overcomes CO poisoning by eliminating the self-poisoning dehydration route. Moreover, tetragonal phase PdO/C with minor Pd (0) at the surface is discovered a highly efficient anti-poisoning ...

Herein, we report the first successful fabrication of sea urchin-like ternary cobalt phosphosulfide (CoPS) nanoneedles in the tetragonal phase on carbon paper (CoPS/CP). The results show that the CoPS/CP exhibits comparable performance to Pt towards the electrochemical HER with the same catalyst loading. Specifically, in 0.5 M H2SO4, this sea urchin-like CoPS hybrid exhibits a negligible onset overpotential of ∼4 mV and a small Tafel slope of 42.6 mV dec−1, and the turnover frequency (TOF) reaches as high as 0.18 s−1 at an overpotential of 100 mV. Additionally, this CoPS/CP electrode shows excellent catalytic durability (100 hours) under both acidic and basic conditions. Density functional theory (DFT) calculations indicated that CoPS exhibits the most suitable hydrogen adsorption free energy (−0.12 eV). This work will open an exciting new direction for the rational design and scalable fabrication of easily-prepared, cost-effective, highly active and robust non-noble metal catalysts for energy storage and conversion, and other applications.

The hydrogen evolution reaction is a crucial step in electrochemical water splitting. The most efficient catalysts for this reaction in acidic media are Pt based, but the high cost of Pt limits its practical applications. We developed a novel matrix architecture in which a trace amount of Pt is alloyed in situ with Ru nanoparticles uniformly and partially embedded in porous carbon spheres. The synthetic procedure is simple and efficient. Surface enrichment of metallic Pt nanoclusters on PtRu alloy nanoparticles results in weak bonding with hydrogen and rapid hydrated proton dissociation. These effects significantly increase the electrocatalytic activity in the hydrogen evolution process. This robust catalyst, with a Pt loading 99.9% less than that of a commercial Pt-based catalyst, gave a high turnover frequency (4.03 H2 s−1), a small Tafel slope (27.2 mV dec−1), and comparable overpotentials (19.7 mV and 43.1 mV), as well as achieved current densities of 10 and 100 mA cm−2, i.e., better than those obtained with commercial Pt/C catalyst, in 0.5 M H2SO4. This structure prevents nanoparticles from dissolving, agglomerating, and detaching during long-term operation; therefore there was no obvious decrease in catalytic activity after continuous reaction.

In this study, a ternary TePbPt alloy nanotube (NT) catalyst was designed based on the following rational considerations. Pb and Te, which could facilitate the removal of adsorbed CO-like intermediates via bifunctional mechanisms and adjust the electronic structure of Pt, respectively, were introduced into the alloy NT catalyst. The as-designed alloy NT catalyst with a uniform, ultrathin, and ultralong structure was precisely prepared through the hard template method with pre-synthesized TePb nanowires used as the sacrificial template. The NT catalyst exhibits excellent performances towards methanol oxidation reaction (MOR) both in activity and durability in an acidic medium. Further characterizations reveal that the enhanced performances are attributed to the adjusted electronic and chemical structures of Pt via the interactions among Pt, Te, and Pb according to complex mechanisms, which are illustrated in detail.

Pesticides have been used extensively in the field of plant protection to maximize crop yields. However, the long-term, unmanaged application of pesticides has posed severe challenges such as pesticide resistance, environmental contamination, risk in human health, soil degradation, and other important global issues. Recently, the combination of nanotechnology with plant protection strategies has offered new perspectives to mitigate these global issues, which has promoted a rapid development of NCs-based pesticides. Unlike certain conventional pesticides that have been applied inefficiently and lacked targeted control, pesticides delivered by nanocarriers (NCs) have optimized formulations, controlled release rate, and minimized or site-specific application. They are receiving increasing attention and are considered as an important part in sustainable and smart agriculture. This review discussed the limitation of traditional pesticides or conventional application mode, focused on the sustainable features of NCs-based pesticides such as improved formulation, enhanced stability under harsh condition, and controlled release/degradation. The perspectives of NCs-based pesticides and their risk assessment were also suggested in this view for a better use of NCs-based pesticides to facilitate sustainable, smart agriculture in the future.

The M–N–C catalysts are considered potential alternative to Pt-based catalysts for the oxygen reduction reaction (ORR) due to its low cost and promising electrocatalytic performance. However, the catalysts are yet to become truly applicable in terms of activity and stability, and addressing such issues necessitate for indepth understanding in the structure performance relationship, which is remain elusive to date. Herein, we summarize our research progress achieved on M–N–C catalysts in recent years. Firstly, we successfully synthesized atomically dispersed Fe–N–C catalysts and conducted a detailed in-situ spectroscopy study, where the high spin D2 states of FeN4 is found to be an active species. Subsequently, in order to address the catalyst utilization and the overall activity of the catalysts, we carried out studies in increasing the active site density through regulating the microstructure of the catalysts. Finally and most importantly, in order to address the intrinsic activity of the catalysts, we carried work in developing new active centers of the M–N–C catalysts, where the new single or dual center catalysts were developed. Some of these centers are able to increase the stability of the catalysts, where the Fenton reaction is largely alleviated, resulting in both enhanced catalytic activity and stability. We hope that as the research continues, commercially available high performance and high stability M–N–C catalysts may eventually be realized.

Summary Fuel cells are promising energy conversion devices which do not require the electrical charging process in comparison with a traditional secondary battery. Polymer electrolyte membrane fuel cells (PEMFCs), including direct methanol fuel cells (DMFCs), are the key technologies in the future due to the high energy conversion efficiency, low emission, and high energy density. DMFCs are promising to be used in mobile electronic devices (power under a few hundred watts) due to the easily and safely transport feature of methanol. Platinum is regarded as the most effective catalyst for the methanol oxidation reaction (MOR). However, the poor performance and the high cost of Pt block the DMFC large-scale applications. The essential method to overcome this shortfall is to develop effective modified-Pt, low-Pt and non-Pt catalysts. This short review paper will focus on the solution to improve the performance of anode MOR in the past 2 years. The structure of this article displays in Figure 1.

An in situ micro-MEA technique, which could precisely measure the performance of ORR electrocatalyst using Nafion as electrolyte, was designed and compared with regular thin-film rotating-disk electrode (TFRDE) (0.1 M HClO4) and normal in situ membrane electrode assembly (MEA) tests. Compared to the traditional TFRDE method, the micro-MEA technique makes the acquisition of catalysts’ behavior at low potential values easily achieved without being limited by the solubility of O2 in water. At the same time, it successfully mimics the structure of regular MEAs and obtains similar results to a regular MEA, thus providing a new technique to simply measure the electrode activity without being bothered by complicated fabrication of regular MEA. In order to further understand the importance of in situ measurement, Fe–N–C as a typical oxygen reduction reaction (ORR) free-Pt catalyst was evaluated by TFRDE and micro-MEA. The results show that the half wave potential of Fe–N–C only shifted negatively by −135 mV in co...