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In this work, a three-component catalyst PdCu/Ag is synthesized using the partial galvanic displacement of copper by silver from the PdCu deposit (~24 at.% Cu) prepared using the electrochemical co-deposition of Pd and Cu (Au support, 0.5 M H2SO4). The composite is characterized by a variety of methods. It is shown that during the galvanic displacement, both Cu and Pd are displaced by silver. The PdCu/Ag catalyst demonstrates higher specific (~twofold) and mass activity (~70-fold) in the reaction of formic acid electrooxidation (FAOR) as compared with individual Pd deposits. The possible factors responsible for the higher Pd activity in the presence of both incorporated Cu and Ag are discussed. [ABSTRACT FROM AUTHOR]

Electrochemical formic acid oxidation reaction (FAOR) is a pivotal model for understanding organic fuel oxidation and advancing sustainable energy technologies. Here, we present mechanistic insights into a novel molecular‐like iridium catalyst (Ir−N4−C) for FAOR. Our studies reveal that isolated sites facilitate a preferential dehydrogenation pathway, circumventing catalyst poisoning and exhibiting high inherent activity. In situ spectroscopic analyses elucidate that weakly adsorbed intermediates mediate the FAOR and are dynamically regulated by potential‐dependent redox transitions. Theoretical and experimental investigations demonstrate a parallel mechanism involving two key intermediates with distinct pH and potential sensitivities. The rate‐determining step is identified as the adsorption of formate via coupled or sequential proton‐electron transfer, which aligns well with the observed kinetic properties, pH dependence, and hydrogen/deuterium isotope effects in experiments. These findings provide valuable insights into the reaction mechanism of FAOR, advancing our understanding at the molecular level and potentially guiding the design of efficient catalysts for fuel cells and electrolyzers. [ABSTRACT FROM AUTHOR]

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Controlled synthesis of one‐dimensional materials at atomic‐scale dimensions represents a milestone in nanotechnology, offering the potential to maximize atom utilization while enhancing catalytic performance. However, achieving structural stability and durability at such fine scales requires precise control over material structure and local chemical environment. Here, we introduce dimethylamine (DMA) as a small‐molecule modifier, in contrast to conventional long‐chain surfactants, to interact with surface Pt atoms. This approach facilitates the removal of surface Pt atoms bonded to nitrogen atoms in DMA during solubilization in water, effectively stripping the size of Pt nanowires down to sub‐nanometer. The resulting Pt subnanometer nanowires (subNWs) feature a monoatomic‐layer surface composed of disordered, bonding‐unsaturated Pt atoms, and an interior crystalline core as narrow as 0.58 nm in diameter. These unique structural characteristics confer the Pt subNWs with an electrochemically active surface‐area of 189 m2 ⋅ g−1 during formic acid oxidation. Furthermore, the amorphous‐like surface structure lowers the free energy of *OCOH intermediates and inhibits the formation of toxic byproducts CO, demonstrating exceptional electrocatalytic activity of 18.1 A ⋅ mg−1, surpassing most reported Pt‐based electrocatalysts. Our work introduces a novel strategy for the controlled construction of nanowire‐structures at sub‐nanometer scale, effectively bridging the gap between ultrafine structural design and performance stability. [ABSTRACT FROM AUTHOR]

The rational design of the electronic structure and elemental compositions of anode electrocatalysts for formic acid electrooxidation reaction (FAOR) is paramount for realizing high‐performance direct formic acid fuel cells. Herein, palladium‐boride nanoflowers (Pd‐B NFs) with controllable boron content are rationally designed via a simple wet chemical reduction method, utilizing PdII‐dimethylglyoxime as precursor and NaBH4 as both reductant and boron source. The boron content of Pd‐B NFs can be regulated through manipulation of reaction time, accompanying with the crystal phase transition from face‐centered cubic to hexagonal close‐packed within the parent Pd lattice. The obtained Pd‐B NFs exhibit increased FAOR mass and specific activity with increasing boron content, showcasing remarkable inherent stability and anti‐poisoning capability compare to commercial Pd and platinum (Pt) nanocrystals. Notably, the sample reacted for 12 h reveals high FAOR specific activity (31.5 A m−2), which is approximately two times higher than the commercial Pd nanocrystals. Density functional theory calculations disclose that the d‐sp orbital hybridization between Pd and B modifies surface d‐band properties of Pd, thereby optimizing the adsorption of key intermediates and facilitating FAOR kinetics on the Pd surface. This study paves the way toward the utilization of metal boride‐based materials with simple synthesis methods for various electrocatalysis applications. [ABSTRACT FROM AUTHOR]

Abstract Platinum-based catalysts that have long been used as the anodes for the formic acid electro-oxidation (FAO) in the direct formic acid fuel cells (DFAFCs) were susceptible to retrogradation in performance due to CO poisoning that impaired the technology transfer in industry. This work is designed to overcome this challenge by amending the Pt surface sequentially with nanosized cobalt (nano-CoOx, fibril texture of ca. 200 nm in particle size) and iron (nano-FeOx, nanorods of particle size and length of 80 and 253 nm, respectively) oxides. This enriched the Pt surface with oxygenated groups that boosted FAO and mitigated the CO poisoning. The unfilled d-orbitals of the transition metals and their tendency to vary their oxidations states presumed their participation in a faster mechanism of FAO. Engineering the Pt surface in this FeOx/CoOx/Pt hierarchy resulted in a remarkable activity toward FAO, that exceeded four times that of the Pt catalyst with up to ca. 2.5 times improvement in the catalytic tolerance against CO poisoning. This associated a ca. − 32 mV shift in the onset potential of FAO which increased to − 40 mV with a post-activation of the same catalyst at − 0.5 in 0.2 mol L–1 NaOH, displaying the catalyst's competitiveness in reducing overpotentials in DFAFCs. It also exhibited a favorable amelioration in the catalytic durability in long-termed chronoamperometric electrolysis. The electrochemical impedance spectroscopy and the CO stripping voltammetry were employed to elucidate the origin of enhancement.

The rapid development of direct formic acid fuel cell (DFAFC) and direct methanol fuel cell (DMFC) technologies urgently needs to explore efficient and multifunctional electrocatalysts with acceptable costs. In this work, we introduce a convenient soft-chemistry method for the bottom-up synthesis of two-dimensional (2D) ultrathin PdMo bimetallene in situ immobilized on reduced graphene oxide nanosheets (PdMo/RGO) by a robust stereoassembly procedure. The as-derived PdMo/RGO nanoarchitecture possesses a range of unique structural advantages tailored for anodic fuel cell systems, such as numerous exposed Pd atoms, bimetallic alloy and strain effects, stable 2D/2D heterointerfaces, and good electrical conductivity. As a result, the PdMo/RGO nanoarchitecture exhibits a large electrochemically active surface areas of 122.2 m2 g−1, a high mass activity of 994.8 mA mg−1, as well as reliable long-term durability towards the formic acid oxidation reaction. Meanwhile, the PdMo/RGO electrocatalyst also displays exceptional electrocatalytic methanol oxidation performance with a mass activity of 1605.3 mA mg−1 in alkaline medium, which significantly surpasses that of conventional Pd nanoparticle catalysts loaded on reduced graphene oxide, carbon nanotube, and carbon black matrices. [Display omitted] • The bottom-up synthesis of 2D PdMo bimetallene on graphene nanosheets is achieved. • Ultrathin PdMo bimetallene provides abundant exposed Pd atoms as well as alloy and strain effects. • The intimate 2D/2D heterointerface generates strong synergistic coupling effects. • The derived nanoarchitecture exhibits superior catalytic performance for both formic acid and methanol oxidation. [ABSTRACT FROM AUTHOR]

Pd-based anode catalysts with superior activity are urgent for formic acid oxidation to further boost the direct formic acid fuel cells (DFAFCs) technologies. Herein, a strategy of ethylenediamine (EDA) modified Pd/C catalyst was developed by two main steps of EDA adsorbed on Vulcan XC-72 carbon by impregnation and Pd nanoparticles loaded on the freeze-dried C-EDA supports by liquid reduction method. The effects of sweep rates and concentrations of EDA on the formic acid electrooxidation were systematically studied. Results showed that the above parameter was optimized as the concentration of EDA of 0.1 mol L−1. Pd nanoparticles with even distribution were fabricated and particle sizes were in the range of 3.5–4.2 nm. In addition, Pd particle size became smaller with the addition of EDA, suggesting that EDA could induce the generation of smaller Pd. Electrochemical measurements demonstrated that the electrocatalytic activity of Pd/C-0.22EDA (1021 mA mg−1) with optimized modification concentration was improved as a factor of 3.82 than that of Pd/C (267 mA mg−1). An enhanced stability (about 41 times higher than Pd/C) and faster charge-transfer kinetics of formic acid electrooxidation were observed for Pd/C-0.22EDA catalyst. CV and CA measurements showed that the most active catalyst was made of the smallest (3.5 nm) Pd nanoparticles for Pd/C-0.22EDA catalyst. The better electrocatalytic performances of Pd/C-0.22EDA might be ascribed to evenly dispersed Pd with relatively smaller particle size, electron regulation between Pd and amine group as well as stable Pd structure. • Ethylenediamine modified Pd/C was firstly prepared to enhance properties of formic acid oxidation. • The adding of EDA contributed to form fine and stable Pd with even distribution. • The modification of EDA greatly enhanced electrocatalytic activity and stability. • The mechanism of enhanced electrocatalytic performances for Pd/C-EDA was discussed. [ABSTRACT FROM AUTHOR]

Platinum-based catalysts that have long been used as the anodes for the formic acid electro-oxidation (FAO) in the direct formic acid fuel cells (DFAFCs) were susceptible to retrogradation in performance due to CO poisoning that impaired the technology transfer in industry. This work is designed to overcome this challenge by amending the Pt surface sequentially with nanosized cobalt (nano-CoOx, fibril texture of ca. 200 nm in particle size) and iron (nano-FeOx, nanorods of particle size and length of 80 and 253 nm, respectively) oxides. This enriched the Pt surface with oxygenated groups that boosted FAO and mitigated the CO poisoning. The unfilled d-orbitals of the transition metals and their tendency to vary their oxidations states presumed their participation in a faster mechanism of FAO. Engineering the Pt surface in this FeOx/CoOx/Pt hierarchy resulted in a remarkable activity toward FAO, that exceeded four times that of the Pt catalyst with up to ca. 2.5 times improvement in the catalytic tolerance against CO poisoning. This associated a ca. − 32 mV shift in the onset potential of FAO which increased to − 40 mV with a post-activation of the same catalyst at − 0.5 in 0.2 mol L–1 NaOH, displaying the catalyst's competitiveness in reducing overpotentials in DFAFCs. It also exhibited a favorable amelioration in the catalytic durability in long-termed chronoamperometric electrolysis. The electrochemical impedance spectroscopy and the CO stripping voltammetry were employed to elucidate the origin of enhancement. [ABSTRACT FROM AUTHOR]

Global energy sources are limited, and energy requirements are ever-increasing due to the demand for developments in human life and technology. The environmentally friendly direct formic acid fuel cell (DFAFC) is an attractive electronic device due to its clean energy. In a DFAFC, an anodic catalyst plays an important role concerning the oxidation pathway and activity. In the present study, palladium (Pd) was synthesized by synchrotron X-ray photoreduction using various irradiation times (0.5–4 min) to control the particle size. An acid-treated carbon nanotube (A-CNT) was used as the template for Pd deposition. The A-CNT and Pd/A-CNT were examined using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy to reveal the microstructural characteristics. Electrochemical evaluation, electrocatalytic activity, and the DFAFC performance of so-obtained Pd/A-CNT catalysts were investigated. The experiment's results showed that the Pd/A-CNT-2 (i.e., synchrotron photoreduction for 2 min) underwent a direct formic acid oxidation pathway and possessed a high ECSA value of 62.59 m2/gPd and superior electrocatalytic activity of 417.7 mA/mgPd. In a single DFAFC examination, the anodic Pd/A-CNT-2 catalyst had a power density of 106.2 mW/mgPd and a relatively long lifetime of 2.91 h. Pd/A-CNT-2 anodic catalysts synthesized by surfactant-free synchrotron X-ray photoreduction with a rapid processing time (2 min) are potential candidates for DFAFC applications. [ABSTRACT FROM AUTHOR]

In this study, a novel cobalt-doped cerium oxide (CeO2)on reduced graphene oxide (rGO) substrate was successfully prepared through a hydrothermal method. The comprehensive characterization of the synthesized nanocomposite involved X-ray diffraction studies (XRD), Raman spectrum analysis, High Resolution Transmission Electron microscopy (HRTEM), and Field Emission Electron Microscopy (FE-SEM). The effective surface area of CeO2/rGO and Co-CeO2/rGO was determined using the Randles-Sevecik equation, revealing values of 4.02X10-5 cm2 and 6.35X10-5 cm 2, respectively. Cyclic Voltammetry (CV) was employed to investigate the electrochemical reversibility behavior, demonstrating promising results for Co-CeO2/rGO nanocomposite. Electrochemical impedance spectroscopy(EIS) further highlighted low charge transfer resistance (Rct) and enhanced double-layer capacitance (Cdl). Notably, the synthesized nanocomposite exhibited excellent electrocatalytic activity for methanol and formic acid oxidation in an acidic medium. Overall, this work provides valuable insights into the synthesis characterization, and electrochemical performance of Co-CeO2/rGO nanocomposite, showcasing their potential applications in energy-related processes. [ABSTRACT FROM AUTHOR]

Direct formic acid fuel cells (DFAFCs) have become an important technology and a clean energy source for various applications. However, some drawbacks in DFAFC applications, such as sluggish kinetics of formic acid oxidation (FAO) reaction at the anodic side, significantly affect DFAFC performance. An excellent catalyst, platinum (Pt), is very effective and performs excellently in FAO, but it is expensive and tends to form carbon monoxide-poisoning species on the catalyst surface. Therefore, new strategies must be developed to overcome problems related to Pt and simultaneously reduce or replace the use of Pt catalysts. This review paper covers the electrocatalytic activities of platinum and palladium (Pd)-based catalysts, which are commercial catalysts and effective for FAO and DFAFC applications. In this paper, the current progress of electrocatalyst development for anodic FAO and DFAFC applications using commercial Pt and Pd catalysts is presented, focusing on the understanding of Pt and Pd catalytic activities with the addition of alloys, metallic metals, trimetallic/tetrametallic metals, transition metals, and metal oxides. Highly potential nanostructured carbon catalyst supports (graphene-based materials, carbon nanotubes, carbon nanofibers, and graphitic carbon nitride) for FAO and DFAFC applications are also discussed. This review article also examines the literature related to Pt and Pd electrocatalysts on the synthesis routes, electrochemical conditions, and fuel cell performance within 10 years from 2013 until 2023. The challenges and strategies for electrocatalyst commercialization in the field are discussed at the end of the paper.

Nowadays, PdCu alloy nanocatalyst with excellent performance in electrocatalytic formic acid oxidation reaction (FAOR) is believed to have great potential in application of direct formic acid fuel cells. Structural engineering has shown great success in achieving PdCu alloys with high catalytic performance, while achievement of multi‐scale structure engineering is still a great challenge. In this work, we found that supercritical carbon dioxide (SC CO2) could lead to multi‐scale structure engineering in PdCu/C nanocatalysts, including surface defect engineering, phase engineering, morphology engineering and substrate structure engineering. With the assistance of SC CO2, amorphous phase in surface, the transformation from face‐centered cubic (FCC) to body‐centered cubic (BCC) phase, the morphology of 2D nanoflakes and the curved carbon as substrate all contribute to the ultrahigh mass activity for electrocatalytic FAOR as 3624.3 mA/mgPd in PdCu/C nanocatalysts, which is the highest value in PdCu alloy reported up to now. Therefore, this work not only displays the great potential of SC CO2 in multi‐scale structure engineering, but also provides new inspiration of material design to achieve nanocatalysts with ultrahigh catalytic performance. [ABSTRACT FROM AUTHOR]

Pd-based catalysts supported on high-surface-area carbon are widely used in formic acid fuel cells. The composition, structure, and support can be modified to maximize the capabilities of Pd-based catalysts in terms of catalytic activity, durability, and cost. Various studies have investigated tuning the properties of Pd-based catalysts by alloying Pd with other metals. In this study, Cr, Ni, Cu, and Zn were incorporated into Pd-based catalysts. First, the effects of mole ratios were studied between Pd and the metals. The PdnNi ratios on a reduced graphene oxide support (PdnNi/rGO) were prepared using the one-pot method without the use of any surfactants. All obtained rGO-supported PdnNi catalysts (n = 1, 2, 4, with diameter of 5 nm) were used for the electrocatalytic oxidation of formic acid. The electro-oxidation measurements revealed that the PdnNi/rGO samples had superior electrocatalytic performance both in current densities and stabilities for formic acid oxidation (FAO) compared to Pd/rGO. Furthermore, Pd4Ni/rGO had greater electrocatalytic activity than the other PdnNi/rGO samples. In addition, with the same mole ratio of metals, Pd4Cr/rGO had higher efficiency toward FAO than the other series in the order: Pd4Cr/rGO > Pd4Ni/rGO > Pd4Cu/rGO > Pd4Zn/rGO. [ABSTRACT FROM AUTHOR]

[Display omitted] • The catalytic effect of bismuth on Pt(1 0 0) electrodes for the FAOR is linked to the Pt-Bi ensembles. • Bismuth catalyzes the direct path and inhibits the CO formation route. • A mechanism for the reaction that accounts for the experimental results is proposed. The formic acid oxidation reaction (FAOR) on bismuth-modified Pt(1 0 0) is studied using electrochemical techniques and FITR spectroscopy at different bismuth coverages and formic acid concentrations. The results clearly show that: (1) The measured currents for the Bi-modified Pt(1 0 0) surface contain contributions from both the Pt-Bi ensembles and the Pt sites far from the Bi adatoms. (2) The catalytic effect of bismuth is not linked to the adsorption of formate on Pt sites. (3) The bismuth not only improves the activity of the FAOR through the active intermediate but also inhibits the CO poison by a third-body effect. (4) The experimental results indicate that the catalytic activity is linked to the Pt-Bi ensembles. The active species, formate, adsorbs on the Bi site and the neighboring Pt sites facilitate the cleavage of the C–H bond. (5) From the concentration dependence, the reaction order for formate on bismuth-modified Pt(1 0 0) is 1 at low potentials. In contrast, a reaction order of 0.5 is obtained at higher potentials. These results are in agreement with the proposed mechanism. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the effect of a RuO2 support on the activity of Pd nanoparticles for formic acid oxidation, comparing the results with those obtained for Pd/C. In contrast with reports of enhancing effects of RuO2 for other systems, such as methanol oxidation on Pt particles, our data reveal a detrimental effect of the RuO2 support on the activity of Pd nanoparticles for the oxidation of formic acid. FTIR spectra show CO2 formation at potentials as low as 0.10 V and absence of adsorbed CO signals, suggesting that a bifunctional mechanism involving OH species on the oxide support surface does not occur nor has a significant contribution and that formic acid oxidation on Pd/RuO2 and Pd/C takes place by the direct pathway. The unfavorable effect of the RuO2 support on activity seems likely to be due to metal-support interactions that modify the Pd electronic properties. [ABSTRACT FROM AUTHOR]

Direct formic acid fuel cells (DFAFCs) have become an important technology and a clean energy source for various applications. However, some drawbacks in DFAFC applications, such as sluggish kinetics of formic acid oxidation (FAO) reaction at the anodic side, significantly affect DFAFC performance. An excellent catalyst, platinum (Pt), is very effective and performs excellently in FAO, but it is expensive and tends to form carbon monoxide-poisoning species on the catalyst surface. Therefore, new strategies must be developed to overcome problems related to Pt and simultaneously reduce or replace the use of Pt catalysts. This review paper covers the electrocatalytic activities of platinum and palladium (Pd)-based catalysts, which are commercial catalysts and effective for FAO and DFAFC applications. In this paper, the current progress of electrocatalyst development for anodic FAO and DFAFC applications using commercial Pt and Pd catalysts is presented, focusing on the understanding of Pt and Pd catalytic activities with the addition of alloys, metallic metals, trimetallic/tetrametallic metals, transition metals, and metal oxides. Highly potential nanostructured carbon catalyst supports (graphene-based materials, carbon nanotubes, carbon nanofibers, and graphitic carbon nitride) for FAO and DFAFC applications are also discussed. This review article also examines the literature related to Pt and Pd electrocatalysts on the synthesis routes, electrochemical conditions, and fuel cell performance within 10 years from 2013 until 2023. The challenges and strategies for electrocatalyst commercialization in the field are discussed at the end of the paper. [ABSTRACT FROM AUTHOR]

A PdAg deposit containing ~ 25 at.% Ag is obtained by the electrochemical codeposition from an aqueous solution of Pd and Ag sulfates (Au support, 0.5 M H2SO4). The deposit is characterized by means of various physical, physicochemical, and electrochemical methods. The PdAg deposit demonstrates the ~ 2 times higher specific activity (per the electrochemically active surface area (EASA) of Pd) in the formic acid oxidation reaction (FAOR) as compared with the individual Pd deposit prepared under the same conditions. The effect of silver additions on the palladium activity depends on many factors. The corrosion stability of PdAg is studied in 0.5 M H2SO4 solution based on the overall cyclic voltammograms (CVAs) and also on anodic and cathodic half-cycles in the region E = 0.3 − 1.25 V (vs. reversible hydrogen electrode (RHE)). The electrochemical estimates are compared with the results of direct analytical determination of dissolution products in solution after anodic polarization of deposits. The total amounts of Pd dissolved substantially increase with incorporation of Ag, which is associated, first of all, with the considerable increase in the EASA; at the same time, the specific dissolution of Pd also substantially increases. The possible factors determining the active dissolution of PdAg deposits are discussed; in particular, the specific mechanism of their dissolution via silver adatoms is proposed. [ABSTRACT FROM AUTHOR]

Bimetallic Pd-based catalysts for formic acid oxidation (FAO) are one of the most promising anode materials for the next generation of direct formic acid fuel cells (DFAFC). It is imperative to develop a simple strategy for preparing efficient, stable, and clean nanoparticle catalysts. Herein, we prepared a series of Pd, PdNi, and PdCo nanoparticle catalysts using the nanoparticle beam composite deposition system, which revealed good catalytic activity and stability in the process of FAO. The incorporation of Ni or Co prevents the adsorption of active intermediates and the accumulation of toxic intermediates in the process of FAO. Therefore, more Pd active centers can be used to decompose formic acid directly by dehydrogenation. The results indicate that PdNi-2 (Pd0.9Ni0.1) and PdCo-3 (Pd0.89Co0.11) catalysts exhibit the optimal catalytic performance, with the mass activity of 1491.5 A g−1Pd and 1401.7 A g−1Pd, respectively, which is 2.1 and 2 times that of the pure Pd sample. By optimizing the rate of Pd to transition metal M (Ni, Co), a high-performance Pd-based catalyst was obtained through their synergistic effect, which provides a new approach for designing efficient anode catalysts for DFAFCs. [ABSTRACT FROM AUTHOR]

The formic acid oxidation reaction (FAOR) represents an important class of small organic molecule oxidation and is central to the practical application of fuel cells. In this study, we report the fabrication of Ir(IV)-doped PdAg alloy nanodendrites with sub-5 nm branches via stepwise synthesis in which the precursors of Pd and Ag were co-reduced, followed by the addition of IrCl3 to conduct an in situ galvanic replacement reaction. When serving as the electrocatalyst for the FAOR in an acidic medium, Ir(IV) doping unambiguously enhanced the activity of PdAg alloy nanodendrites and improved the reaction kinetics and long-term stability. In particular, the carbon-supported PdAgIr nanodendrites exhibited a prominent mass activity with a value of 1.09 A mgPd−1, which is almost 2.0 times and 2.7 times that of their PdAg and Pd counterparts, and far superior to that of commercial Pt/C. As confirmed by the means of the DFT simulations, this improved electrocatalytic performance stems from the reduced overall barrier in the oxidation of formic acid into CO2 during the FAOR and successful d-band tuning, together with the stabilization of Pd atoms. The current study opens a new avenue for engineering Pd-based trimetallic nanocrystals with versatile control over the morphology and composition, shedding light on the design of advanced fuel cell electrocatalysts. [ABSTRACT FROM AUTHOR]

Rational design of the proximal coordination of an active site to achieve its optimum catalytic activity is the ultimate goal in single‐atom catalysis, but still challenging. Here, we report theoretical prediction and experimental realization of an asymmetrically coordinated iridium single‐atom catalyst (IrN3O) for the formic acid oxidation reaction (FAOR). Theoretical calculations reveal that the substitution of one or two nitrogen with more electronegative oxygen in the symmetric IrN4 motif splits and downshifts the Ir 5d orbitals with respect to the Fermi level, moderating the binding strength of key intermediates on IrN4−xOx (x=1, 2) sites, especially that the IrN3O motif shows ideal activity for FAOR with a near‐zero overpotential. The as‐designed asymmetric Ir motifs were realized by pyrolyzing Ir precursor with oxygen‐rich glucose and nitrogen‐rich melamine, exhibiting a mass activity of 25 and 87 times greater than those of state‐of‐the‐art Pd/C and Pt/C, respectively. [ABSTRACT FROM AUTHOR]

Core–shell structure Cu@Pd/C catalysts were prepared in two steps combining microwave-assisted glycol reduction and chemical impregnation method for the first time. Compared with the traditional one-step synthesis of PdCu/C alloy catalysts by microwave (marked as M-PdCu/C) and impregnation (denoted by I-PdCu/C) method, respectively. The Cu@Pd/C catalysts were prepared in two-step show better catalytic performance toward formic acid oxidation, due to its special core–shell structure and better dispersion. On this basis, different proportions of Cux@Pdy/C (x:y = 1:1, 1:2, 1:3, 1:4 and 1:5) catalysts were synthesized by the two-step strategy. The relationship between lattice strain, electron distribution and catalytic performance were explored by physical and chemical characterization. X-ray diffraction and X-ray photoelectron spectra analyses showed that the introduction of Cu lead to the lattice contraction and modified electronic structure of Pd. The electrochemical test showed that Cu@Pd3/C sample has the highest activity toward formic acid electro-oxidation. Its mass activity is about 3.3 times that of Pd/C catalyst that was synthesized by impregnation method (labelled as I-Pd/C). At the same time, the Cu@Pd3/C catalyst also demonstrated improved stability. The low-palladium catalyst with a Pd–Cu shell–core structure was synthesized by two-step method and has excellent catalytic activity and stability for formic acid electro-oxidation. [ABSTRACT FROM AUTHOR]

• Development of a hierarchically porous MIL-125(Ti) through PS-template-assisted synthesis and SESA. • Fabrication of a hierarchically porous structure post-template removal. • Photocatalytic activity of H-MIL-125(Ti) improved three-fold compared to P25 for formic acid oxidation. • Excellent reusability and minimal Ti leaching make H-MIL-125(Ti) a sustainable option for environmental remediation. This study presents the synthesis of hierarchically porous holy MIL-125(Ti) (H-MIL-125(Ti)) photocatalyst via a polystyrene (PS)-directed templating approach combined with solvent evaporation self-assembly (SESA). Sacrificial PS microsphere templates facilitated the formation of a macroporous structure, acting as temporary placeholders during metal–organic frameworks (MOF) crystallization. Removal of the templates created a complementary porous network within MIL-125(Ti), yielding a hierarchical pore architecture comprising inherent micropores and templated macropores. Characterization techniques revealed a high surface area (1204 m2 L−1) and optimal band gap (3.2 eV). Photoelectrochemical studies demonstrated efficient charge carrier generation and separation, with high average photocurrent density (4.5 mA cm−2) and low charge transfer resistance (27.5 Ω cm2). H-MIL-125(Ti) exhibited excellent photocatalytic activity for degrading various (volatile)organic pollutants under visible light, highlighting the importance of rational design and synthesis strategies in optimizing the performance of advanced porous materials. [ABSTRACT FROM AUTHOR]

Stabilizers play a critical role in synthesizing small and well-dispersed nanoparticles with large catalytic surface areas. Simultaneously, they strongly bind to the surface of the nanoparticles and interfere with the catalytic reaction. In this study, we report that the effects of stabilizers can be replaced by the periodic and uniform fluid shear of Taylor vortex flow (TVF). Small PdCu alloy nanoparticles well-dispersed on carbon were synthesized in the Couette–Taylor reactor using TVF without the stabilizer. TVF could provide effective micromixing for a fast reaction and uniform fluid shear to prevent aggregation in nanoparticle synthesis, thus forming small and well-dispersed nanoparticles. In contrast, turbulent eddy flow generated by impeller agitation in a mixing tank reactor could only synthesize aggregates of nanoparticles seriously, indicating the importance of the periodic uniform flow. The synthesized stabilizer-free PdCu nanoparticles (Pd41Cu59/C) showed 1.4 times and 3 times higher mass activity than PdCu/C covered with a stabilizer (polyvinylpyrrolidone) and commercial Pd/C toward electrochemical formic acid oxidation, respectively. [ABSTRACT FROM AUTHOR]

The aim of this research was to study the efficiency of polyvinyl alcohol (PVA)‐modified graphene oxide (GO) as a supporting material for catalysts that oxidize formic acid. The active metal catalysts (e.g., Pt and Pd) were electrodeposited on PVA/GO surfaces. The morphologies of the prepared catalysts were characterized by scanning electron microscopy and transmission electron microscopy, while their chemical compositions were identified by X‐ray diffraction and X‐ray photoelectron spectroscopy. The results show that compared with the other catalysts on GO, the prepared active PtPd alloy catalyst nanoparticles with 11.49–20.73 nm sizes were well dispersed on the PVA/GO surfaces. Electrochemical results indicate that the activities of the catalysts with PVA provided a higher current density than that of the catalysts without PVA. The bimetallic 3Pt3Pd/PVA/GO catalyst showed the greatest catalytic activity, stability, and CO oxidation when compared to those of other catalysts. The electronic, morphological, and structural properties promote the mass‐charge transfer through the interaction. These results indicate that the PVA‐modified GO provides a suitable site for active bimetallic catalyst surfaces, resulting in excellent formic acid oxidation and high CO elimination. The 3Pt3Pd/PVA/GO electrocatalyst is promising for enhancing formic acid oxidation. [ABSTRACT FROM AUTHOR]

In this study, the Pd3Co1 alloy nanocluster from a multiwalled carbon nanotube (MWCTN) catalyst was fabricated in deep eutectic solvents (DESs) (referred to Pd3Co1/CNTs). The catalyst shows a better mass activity towards the formic acid oxidation reaction (FAOR) (2410.1 mA mgPd−1), a better anti-CO toxicity (0.36 V) than Pd/CNTs and commercial Pd/C. The improved performance of Pd3Co1/CNTs is attributed to appropriate Co doping, which changed the electronic state around the Pd atom, lowered the d-band of Pd, formed a new Pd-Co bond act at the active sites, affected the adsorption of the toxic intermediates and weakened the dissolution of Pd; moreover, with the assistance of DES, the obtained ultrafine Pd3Co1 nanoalloy exposes more active sites to enhance the dehydrogenation process of the FAOR. The study shows a new way to construct a high-performance Pd-alloy catalyst for the direct formic acid fuel cell. [ABSTRACT FROM AUTHOR]

Developing large-scale platinum (Pt) alloys that simultaneously exhibit high formic acid oxidation reaction (FAOR) activity and robust CO tolerance remains a significant challenge for practical fuel cell applications. Here, a facile and universal in situ synthesis approach is presented to create ultrathin platinum-tellurium nanosheets on carbon support (PtTe 2 NSs/C), which enables high CO tolerance and FAOR activity while achieving the massive production of PtTe 2 NSs/C. Specifically, the 10-gram-scale PtTe 2 NSs/C achieves exceptional specific activity and mass activity of 14.3 mA cm -2 and 3.6 A mg Pt -1 , respectively, which are 52.9 and 22.5 times greater than those of commercial Pt/C. Moreover, the 10-gram-scale PtTe 2 NS/C exhibits significantly higher FAOR stability than pristine Pt NSs/C and commercial Pt/C. Detailed mechanism and computational investigations collectively reveal that the integration of Te into Pt lattices enhances the utilization of Pt while constructing high-density unsaturated "Pt-Te sites" on the surface of PtTe 2 NSs/C, conferring high CO tolerance to PtTe 2 NSs/C and thus substantially enhancing the FAOR activity. This work contributes to providing a universal method for scaling up next-generation high-performing FAOR catalysts., (© 2025 Wiley‐VCH GmbH.)

Direct formic acid fuel cell (DFAFC) is an efficient power generation device, due to its high energy density, low fuel crossover and low emission. However, the anodic reaction of DFAFC, formic acid oxidation (FAOR), inevitably proceeds through an indirect pathway, adsorbing carbon monoxide intermediate (CO ads ), resulting in a rapid decline of activity for FAOR. Therefore, effectively removing CO ads is the key to the development of DFAFC. In this work, Pd/CeO 2 catalyst is synthesized by in situ growth of Pd nanoparticles on the hollow CeO 2 . Due to the difference of work function between Pd and CeO 2 , a built-in electric field from Pd side to CeO 2 side is formed, which induces a synergistic enhancement of the photogenerated carrier density and the local high hydroxyl concentration at the Pd/CeO 2 interface, thus promoting the oxidative removal of CO ads and significantly improving the stability of FAOR. Therefore, in photo-assisted electrocatalytic FAOR, Pd/CeO 2 not only possessed high mass activity (4161.72 mA mg -1 Pd ), and its mass activity decreases by only 20.1% after 40000 s chronoamperometry test, which is superior to most Pd-based catalysts. This work provides a new strategy for efficient removal of CO ads in FAOR through constructing built-in electric fields, which promotes the DFAFC application., (© 2024 Wiley‐VCH GmbH.)

Designing palladium-based formic acid oxidation reaction (FAOR) catalysts to achieve significant breakthroughs in catalytic activity, pathway selectivity, and toxicity resistance is both urgent and challenging. Here, these challenges are addressed by pioneering a novel catalyst design that incorporates both topological and chemical disorder, developing a new class of PdCuLaYMnW high-entropy amorphous alloys with a porous network (Net-Pd-HEAA) as a highly active, selective, and stable FAOR electrocatalyst. This novel Net-Pd-HEAA demonstrates record-breaking FAOR performance, achieving the mass and specific activities of 5.94 A mg Pd -1 and 8.94 mA cm -2 , respectively, surpassing all previously reported Pd-based catalysts and showing strong competitiveness against advanced Pt-based catalysts. Simulataneously, Net-Pd-HEAA exhibits extraordinary stability in accelerated durability tests (ADT) and chronoamperometry (CA) tests. Advanced characterization and in situ, spectral analysis reveal that the extremely disordered atomic structure effectively regulates the geometric and electronic structure of the Pd sites, enhancing active intermediate coverage, facilitating dehydrogenation pathway, and inhibiting the production/adsorption of CO. Furthermore, when employed as the anode catalyst in proton exchange membrane water electrolysis (PEMWE), Net-Pd-HEAA only requires a potential of 1.28 V to obtain a current density of 1 A cm -2 , and operates stably in a highly corrosive electrolyte for over 100 h., (© 2024 Wiley‐VCH GmbH.)

Here, we investigate the band structure, density of states, photocatalytic activity, and heterojunction mechanism of WS2 with CeO2 (CeO2@WS2) as a photoactive heterostructure. In this heterostructure, CeO2′s growth within WS2 layers is achieved through ultrasonicating WS2 and intercalating CeO2′s precursor within the WS2 interlayers, followed by hydrothermal treatment. Through a set of density functional calculations, we demonstrate that CeO2 and WS2 form an interface through a covalent bonding that can be highly stable. The electrochemical impedance spectroscopy (EIS) found that the CeO2@WS2 heterostructure exhibits a remarkably higher conductivity (22.23 mS cm−2) compared to either WS2 and CeO2, assignable to the interface in CeO2@WS2. Furthermore, in a physically mixed CeO2-WS2 where the interaction between particles is noncovalent, the resistance was significantly higher (0.67 mS cm−2), confirming that the heterostructure in the interface is covalently bonded. In addition, Mott-Schottky and the bandgap measurements through Tauc plots demonstrate that the heterojunction in CeO2 and WS2 is type II. Eventually, the CeO2@WS2 heterostructure indicated 446.7 µmol g −1 CO2 generation from photocatalytic oxidation of a volatile organic compound (VOC), formic acid, compared to WS2 and CeO2 alone.

On‐site hydrogen peroxide production through electrocatalytic and photocatalytic oxygen reduction reactions has recently attracted broad research interest. However, practical applications have thus far been plagued by the low activity and the requirement of complex equipment. Here, inspired by the process of biological hydrogen peroxide synthesis catalyzed by enzymes, we report a Pt‐Au alloy to mimic the catalytic function of natural formate oxidase for hydrogen peroxide synthesis through aerobic oxidation of formic acid. The mass activity of the Pt‐Au alloy is three times higher than that of formate oxidase. Density functional theory calculations revealed that the efficient dehydrogenation of formic acid and the high selectivity of the subsequent reduction of oxygen to hydrogen peroxide account for the high hydrogen peroxide productivity. In addition, the formic acid aqueous solution provides an acidic environment, which is conducive to the utilization of the in situ generated hydrogen peroxide for oxidation reactions, including C−H bond oxidation and sterilization. [ABSTRACT FROM AUTHOR]

Exploring reversible Zn–CO2 batteries holds great promising potential for future CO2 fixation and energy supply. Herein, the bifunctional PdBi alloy anchoring on carbon substrate (BiPdC) is proposed for simultaneously catalyzing carbon dioxide reduction reaction (CO2RR) and formic acid oxidation (FAO). The synergistic effect between Pd and Bi overcomes the sluggish kinetics of CO2RR and FAO, causing the HCOOH Faraday efficiency (FEHCOOH) of 63.4% and 6.2 mA cm–2 current density for FAO. Benefiting from the CO2–HCOOH interconversion, the homemade reversible Zn–CO2 battery exhibits the optimal 52.6% FEHCOOH and 1.1 V voltage gap within 45 h of cycling. [ABSTRACT FROM AUTHOR]

Constructing Ni@Pd nanocatalysts can effectively improve the catalytic efficiency of Pd atoms. However, it is difficult to grow Pd atoms uniformly on the Ni surface due to the large lattice mismatch between Ni and Pd. Herein, we demonstrate that the well‐defined Ni@Pd nanocatalysts can be obtained by the galvanic replacement reaction between Ni and Pd at room temperature. By simply regulating the content of Pd precursor in the galvanic replacement reaction, the atomic percentages of Pd can be controlled from 2 % to 9 %. In synthesized Ni@Pd nanocatalysts, the Ni@Pd0.06 core‐shell nanocrystals show the highest mass activity (1186 mA mgPd−1) and specific activity (4.21 mA cm−2), which are 5.6 times and 2.6 times higher than that of the commercial Pd/C nanocatalyst (212 mA mgPd−1, 1.60 mA cm−2). The enhanced performance is mainly attributed to the synergistic effect between Pd and Ni and the core‐shell nanostructure. [ABSTRACT FROM AUTHOR]

Dispersion is a crucial issue in nanoparticle preparation, e.g., a nanocatalyst of a high surface–volume ratio. Unfortunately, most synthetic approaches strongly depend on an excessive amount of stabilizers and inactive supporting materials for nanoparticle dispersion, resulting in a serious loss of the active surface. In this research, an approach employing a Taylor vortex flow (TVF) is first reported to obtain the effective dispersion of nanoparticles in the synthesis. Completely dispersed nanoparticles of the CuPd alloy less than 5 nm were easily synthesized in a continuous Couette–Taylor (CT) reactor due to the strong and periodic shear field of TVF. Thus, 3.2 nm sized nanoparticles were synthesized at a rotation speed of 1200 rpm and a mean residence time of 2 min despite the use of at least 6–14 times less stabilizer compared with conventional synthetic approaches. However, large aggregates of nanoparticles are always produced in a conventional continuous stirring tank reactor (CSTR) even with a high concentration of stabilizer and a high agitation speed of 3000 rpm. Furthermore, we systematically examined the effect of various synthetic parameters such as rotating speeds, mean residence times, and concentrations of reagents and stabilizers on the dispersion and size of CuPd alloy nanoparticles. Moreover, the well-dispersed CuPd alloy nanoparticles prepared in the CT reactor exhibited enhanced electrocatalytic activity for formic acid oxidation (FAO) compared with CuPd aggregates prepared in CSTR. [ABSTRACT FROM AUTHOR]

Formic acid is a promising energy carrier. Electrochemical formic acid oxidation can serve as an important reaction within fuel cells. Although Pt remains the best‐known catalyst, surface adatoms like Pb have been known to promote formic acid electro‐oxidation significantly. We have carried out first principle‐based calculations, bonding analysis, and experiments to provide insights for this enhancement. Results show that upon adsorption of Pb on the Pt surface, an upshift of Pt energy levels above the Fermi energy is observed, which in general influences the binding energy of the adsorbates. Reaction free energy vs. electrochemical potential diagrams were constructed to understand the interaction of formic acid and water with Pt and Pb‐modified Pt surfaces. Electrochemical experiments indicating the underpotentially deposited hydrogen (Hupd) region and potential‐dependent apparent activation energies indicate that Hupd suppression has an important role to play in the formic acid oxidation reaction. The suppression of the Hupd region on Pb‐modified Pt surface results in free Pt sites that can carry out direct formic acid oxidation to CO2. [ABSTRACT FROM AUTHOR]

[Display omitted] • P-Pd nanoparticles were facilely prepared based on polyphosphide chemistry. • The soluble phosphorus anion was used as both P source and reducing agent. • P significantly improves catalytic activity through size and electronic effects. • The P-Pd exhibited surprising anti-CO poisoning ability. • DFT calculations showed the indirect pathway was inhabited by P-doping. In this work, we reported a novel polyphosphide strategy for the synthesis of phosphorus doped Pd (P-Pd) using red phosphorus as the starting material at quasi-ambient conditions. Polyphophide anions, as the key reaction intermediates, served as the reducing agent and phosphorus source to modulate the surface electronic structure of Pd. The P-Pd obtained exhibited topmost CO tolerance and electrocatalytic activity to formic acid oxidation among the state-of-arts reports. The mass activity and turnover frequency of P-Pd reached 4413 mA mg−1 Pd and 16.04 s−1 at 0.8 V, which were 23.7 and 6.4 times that of commercial Pd/C respectively. After 1000 repeated cycles, 82% initial activity was reserved. Combined with the electrochemical analysis and the density functional theory calculation, the boosted electrochemical performances can be attributed to the size and electronic effects induced by the P doping, which increase the surface actives sites, inhibit the adsorption of CO and change the reaction pathway to favorable CO 2 route. A full cell was also assembled to demonstrate the practical potential of the P-Pd, which showed a maximum power density of 21.56 mW cm−2. This polyphophide-based reaction route provides a new strategy for the preparation of efficient and durable phosphorus doped alloys for electrocatalysis. [ABSTRACT FROM AUTHOR]

In this study, the formic acid electro-oxidation reaction (FAEOR) was catalyzed on a Pd-Au co-electrodeposited binary catalyst. The kinetics of FAEOR were intensively impacted by changing the Pd2+:Au3+ molar ratio in the deposition medium. The Pd1-Au1 catalyst (for which the Pd2+:Au3+ molar ratio was 1:1) acquired the highest activity with a peak current density for the direct FAEOR (Ip) of 4.14 mA cm−2 (ca. 13- times higher than that (ca. 0.33 mA cm−2) of the pristine Pd1-Au0 catalyst). It also retained the highest stability that was denoted in fulfilling ca. 0.292 mA cm−2 (ca. 19-times higher than 0.015 mA cm−2 of the pristine Pd1-Au0 catalyst) after 3600 s of continuous electrolysis at 0.05 V. The CO stripping and impedance measurements confirmed, respectively, the geometrical and electronic enhancements in the proposed catalyst.

[Display omitted] Pd-based catalysts with maximized exposure of active sites, ultrafast electron transport, and cocatalyst-promoted intrinsic activity are highly desirable for the formic acid oxidation reaction (FAOR), but their fabrication presents a formidable challenge. For the first time, dynamic self-assembly of adenine has been utilized for growth of ultrasmall, highly dispersed, and clean Pd NPs on pristine graphene. The obtained nanohybrid shows remarkably enhanced FAOR catalytic activity and durability compared to Pd NPs directly grown on pristine graphene and commercial Pd/C. The activity is also among the highest for Pd-based catalysts. The excellent catalytic performance is due to well-dispersed, ultrasmall, and clean Pd NPs intimately grown on pristine graphene offering numerous electrochemically accessible active sites and preserving high intrinsic catalytic activity of Pd, great cocatalytic effect of pristine graphene enhancing CO tolerance and intrinsic activity of Pd, and robust attachment of Pd with high CO tolerance on graphene providing high durability. This study develops a facile, mild, and economical strategy to create pristine graphene supported clean Pd NPs with outstanding FAOR catalytic performance, and also sheds light on the mechanism of dynamically self-assembled adenine-mediated synthesis, which is extendable to fabricate other nanohybrids. [ABSTRACT FROM AUTHOR]

A catalyst composed of 2-acrylamido-2-methyl-1-propane sulfonic acid (PAMPs) modified graphene oxide (GO) as the supporting material (PAMPs/GO) and electrodeposited monometallic and bimetallic catalysts (Pt and/or Pd) as the active catalytic component was fabricated to enhance the formic acid oxidation. The morphology of the prepared catalysts was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the chemical compositions were identified by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Functional groups of the supporting materials and catalysts were identified by Fourier transform infrared (FT-IR) spectroscopy. The electrochemical measurements of the synthesized catalysts were evaluated by cyclic voltammetry (CV) and chronoamperometry (CA), respectively. The kinetics of formic acid oxidation on the synthesized catalysts were determined by Tafel extrapolation of linear sweep voltammograms. The CO tolerance of the electrocatalyst was examined by CO stripping measurements. The results showed that the catalysts with PAMPs exhibited much higher electrocatalytic activity and longer-term stability for formic oxidation than the catalyst without PAMPS. In addition, the 3Pt3Pd/10%PAMPs/GO catalyst showed the greatest catalytic activity, stability, and fastest charge transfer kinetics when compared to other bimetallic catalysts and monometallic catalysts. In conclusion, modifying the GO surface with PAMPs can improve the efficiency of the electrocatalyst activity of Pt/Pd catalysts. The 3Pt3Pd/10%PAMPs/GO catalyst is a promising electrocatalyst for the enhancement of formic acid oxidation. • Dispersed bimetallic PtPd nanoparticles electrodeposited on PAMPs modified GO support were achieved. • Effective catalysts provide better electrocatalytic performance towards oxidation of formic acid. • High activity and stability of the catalyst for formic acid electrooxidation are obviously improved by adding PAMPs and Pd.. [ABSTRACT FROM AUTHOR]