Formic Oxidation Reaction Research Articles

Efficient electrocatalytic formate oxidation on copper oxide catalyst mediated lithium recovery coupled hydrogen production

In response to the increase in retired lithium-ion batteries (LIBs), there is a rising trend in lithium recycling, which can not only address the scarcity of lithium resources but also mitigate environmental pollution caused by battery waste. In this study, we present an electrocatalytic strategy for formate oxidation reaction (FOR) aimed at facilitating lithium recovery coupled hydrogen production. The obtained results have indicated that the synthesized Cu-based oxide can efficiently catalyze FOR, achieving a current density of 500 mA cm−2 at only 1.534 V vs. RHE. According to density functional theory calculations, the adsorption strength of the intermediate specie HCOO on Cu-based oxide is reduced (−0.36 eV) compared to Ni-based oxide (−2.27 eV), resulting in a thermodynamically favorable step for the rate-determining HCOO dehydrogenation reaction. Assembling a FOR coupled hydrogen evolution reaction (HER) electrolysis system can achieve hydrogen production and Li recovery (Li recovery product is Li2CO3) by electrolyzing alkaline raffinate containing lithium. This approach eliminates the need for additional formic acid and sodium carbonate, thereby reducing material consumption and ultimately enhancing the economic efficiency of the lithium battery recovery strategy.

A novel defective PdMo bimetallene with atomic-scale cavities for highly efficient chemicals-assisted hydrogen production

Introducing defects into Pd-based metallene has been shown to significantly enhance its electrocatalytic performance. In this study, we embedded a new type of atomic-scale cavities into the basal plane of PdMo bimetallene (c-PdMo) through precise etching. These cavities introduced tensile strain and increased the generalized coordination number (CN̅), resulting in superior performance in formate oxidation reaction (FOR) and methanol oxidation reaction (MOR), with mass activities of 5.01 mAμgNM−1 and 5.38 mAμgNM−1, respectively. Notably, a two-electrode system comprising commercial Pt/C and c-PdMo coated on carbon paper achieved cell voltages of only 0.517 V and 0.362 V at 10 mA cm−2 for FOR and MOR, respectively. Additionally, density functional theory calculations revealed that the deliberate lattice tensile strain and enhanced coordination numbers reduced the D-band center of defective PdMo, which improved OH adsorption and reduced CO adsorption, thus optimizing FOR and MOR catalysis on the surface of c-PdMo bimetallene.

Synergistic Effect of Trimetallic PdCuIn Nanoparticles in Ethanol and Formate Oxidation Reaction for Remarkable Catalytic Performance

Direct liquid fuel cells (DLFC) are regarded as attractive energy devices with their advantages of sustainability and eco‐friendly operation. Pd‐based materials have been recognized as ideal catalysts for anodic oxidation of DLFC. Although reasonably regulating the structure of Pd‐based catalysts to achieve remarkable catalytic performance, it is not clear about the combined effects of d‐band center and charge transfer, which are the crucial impactors for catalytic activity. Herein, a facile method to synthesize trimetallic PdCuIn nanoparticles (PdCuIn NPs) for ethanol and formate oxidation reactions (EOR and FOR, respectively) is reported. PdCuIn NPs exhibits bifunctional catalytic activities for both EOR and FOR, with mass activities of 16 000 and 15 500 mA mgPd−1, respectively, which are much better than those of commercial Pd/C catalysts. Comparing to the bimetallic nanoparticles (PdCu or PdIn NPs), additional Cu or In enhances the electron transfer and achieves a suitable d‐band center, resulting in excellent performance. This work synthesizes a highly active catalyst for both EOR and FOR, but also provides facile strategy of balancing the d‐band center and charge transfer for high catalytic performance.

Modulating the d-Band Center of Palladium via Ethylene Glycol Modification: Accelerating Had Desorption for Enhanced Formate Electrooxidation.

This study addresses the critical challenge in alkaline direct formate fuel cells (DFFCs) of slow formate oxidation reaction (FOR) kinetics as a result of strong hydrogen intermediate (Had) adsorption on Pd catalysts. We developed WO3-supported Pd nanoparticles (EG-Pd/WO3) via an organic reduction method using ethylene glycol (EG), aiming to modulate the d-band center of Pd and alter Had adsorption dynamics. Cyclic voltammetry demonstrated significantly improved Had desorption kinetics in EG-Pd/WO3 catalysts. Density functional theory (DFT) calculations revealed that the presence of EG reduces the d-band center of Pd, leading to weaker Pd-H bonds and enhanced Had desorption during the FOR. This research provides a new approach to optimize catalyst efficiency in DFFCs, highlighting the potential for more effective and sustainable energy solutions through advanced material engineering.

Cu-Modified Palladium Catalysts: Boosting Formate Electrooxidation via Interfacially OHad-Driven Had Removal.

Direct formate fuel cells have gained traction due to their eco-friendly credentials and inherent safety. However, their potential is hampered by the kinetic challenges of the formate oxidation reaction (FOR) on Pd-based catalysts, chiefly due to the unfavorable adsorption of hydrogen species (Had). These species clog the active sites, hindering efficient catalysis. Here, we introduce a straightforward strategy to remedy this bottleneck by incorporating Pd with Cu to expedite the removal of Pd-Had in alkaline media. Notably, Cu plays a pivotal role in bolstering the concentration of hydroxyl adsorbates (OHad) on the surface of catalyst. These OHad species can react with Had, effectively unblocking the active sites for FOR. The as-synthesized catalyst of PdCu/C exhibits a superior FOR performance, boasting a remarkable mass activity of 3.62 A mg-1. Through CO-stripping voltammetry, we discern that the presence of Cu in Pd markedly speeds up the formation of adsorbed hydroxyl species (OHad) at diminished potentials. This, in turn, aids the oxidative removal of Pd-Had, leveraging a synergistic mechanism during FOR. Density functional theory computations further reveal intensified interactions between adsorbed oxygen species and intermediates, underscoring that the Cu-Pd interface exhibits greater oxyphilicity compared to pristine Pd. In this study, we present both experimental and theoretical corroborations, unequivocally highlighting that the integrated copper species markedly amplify the generation of OHad, ensuring efficient removal of Had. This work paves the way, shedding light on the strategic design of high-performing FOR catalysts.

Structural evolutions under surface oxidation of AgPd Alloy: From Orientation, composition and strain effects to catalytic application

The surface oxidation of AgPd alloys can significantly impact their catalytic activity, however, the detailed understanding of such dynamic mechanism and the prediction of catalytic activity is still lacking. Herein, a comprehensive investigation combining ab initio molecular dynamics simulations with experimental observations is performed. The surface oxidation of AgPd alloys is highly dependent on oxygen concentration, where AgOx forms in oxygen-poor environment and PdOx forms in oxygen-rich environment, and shows highly reliance on the orientation, composition and strain state. The oxidation level of Ag, Pd and AgPd alloys follows the trend of (111) < (100) < (110) under 1.0 ML of O coverage. Both Pd single-atom and Ag matrix atoms in PdAg single-atom alloys are susceptible to oxidation under 0.5 ML of O coverage, with the increase of Pd atom number, only AgOx forms. Tensile strain promotes the oxidation of Ag(111) surface by facilitating the inward diffusion of O atoms, while compressive strain promotes the oxidation of Pd(111) and AgPd(111) surfaces by facilitating the outward migration of Ag/Pd atoms. The oxidized AgPd(111) surface with tensile strain under 0.5 ML of O coverage exhibits the optimum electrocatalytic activity toward formate oxidation reaction.

Hierarchical AgNi Alloy@NiO/Ni(OH)2 nanosheets on Ni foam as 3D electrode towards methanol and formate oxidation

Direct liquid fuel cells (DLFCs) are regarded as promising technologies for clean energy conversion. However, the high cost of platinum-group-metal catalysts and the unsatisfactory performance of electrodes still limit their applications in DLFCs. Developing robust and low-cost electrode is highly desired for DLFC applications. In this paper, hierarchical NiO/Ni(OH)2 with the anchor of AgNi alloy is constructed on Ni foam through hydrothermal and annealing procedures. The constructed electrode is used for both formate oxidation reaction (FOR) and methanol oxidation reaction (MOR) in alkaline media. The electrochemical measurements suggest that the as-prepared electrodes exhibit high net oxidation current densities of 37.6 and 41.6 mA/cm2 at 1.5 V toward FOR and MOR, respectively, and show a satisfactory stability through chronoamperometric tests. These results demonstrate that the constructed electrodes through a facile pathway are promising to serve as high-efficient 3D binder-free electrodes for practical applications.

Stable Strain State of Single‐Twinned AgPdF Nanoalloys under Formate Oxidation Reaction

Surface reconstruction as common phenomenon during catalysis complicates the prediction and modeling on catalytic activity of the nanoalloy, hence developing a stable structure to be resistant to surface restructuring would provide an ideal prototype for substantial and reliable mechanism analysis. Herein, the single‐twinned structure in inverse AgPdF catalyst is constructed to enhance the catalytic activity and stability for the formate oxidation reaction (FOR). The single‐twinned AgPdF nanoalloy (t‐AgPdF) catalyst exhibits an enhanced peak current density of 4.6 A mgPd−1, a reduced onset potential of 0.44 V, a higher activity retention of 55.7% after 600 cycles, and a longer activity retention time of 55.9 h. Additionally, the t‐AgPdF catalyst presents a higher hydrogen generation rate of 1.11 mL mgPd−1 than that of single‐crystalline AgPd nanoalloy (AgPd) catalyst, and density functional theory calculations reveal that t‐AgPdF(111) surface exhibits a reduced activation energy of 0.59 eV for formate decomposition reaction. Impressively, the t‐AgPdF maintains compressive and tensile strain state along the Σ3 twin boundaries before and after the FOR, in contrast to AgPd. This is the first time to reveal that the nanotwinned structures contribute inverse t‐AgPdF catalysts the catalytic active sites with stable strain state since starting reaction for the FOR.

Modulating the Interfacial Water Network of Dual-Site Pd/FeOx/C Catalyst for Efficient Formate Electrooxidation.

The rational design of electrocatalysts for formate oxidation reaction (FOR) in alkaline media is crucial to promote the practical applications of direct formate fuel cells (DFFCs). The FOR kinetic on palladium (Pd) based electrocatalysts is strongly hindered by unfavorably adsorbed hydrogen (Had) as the major intermediate species blocking the active sites. Herein, we report a strategy of modulating the interfacial water network of dual-site Pd/FeOx/C catalyst to significantly enhance the desorption kinetics of Had during FOR. Aberration-corrected electron microscopy and synchrotron characterizations revealed the successful construction of Pd/FeOx interfaces on carbon support as a dual-site electrocatalyst for FOR. Electrochemical tests and in situ Raman spectroscopy results showed that Had could be effectively removed from the active sites of the as-designed Pd/FeOx/C catalyst. CO-stripping voltammetry and density functional theory calculations (DFT) demonstrated that the introduced FeOx could effectively accelerate the dissociative adsorption of water molecules on active sites, which accordingly generates adsorbed hydroxyl species (OHad) to facilitate the removal of Had during FOR. This work provides a novel route to develop advanced FOR catalysts for fuel cell applications.

Component dependent electrocatalytic activity of magnetic bimetallic Pd-Ni nanoparticles for formate oxidation

Formate fuel cells require efficient and stable electrocatalysts for formate oxidation reaction (FOR). Pd-Ni nanoparticles (NPs) with tuned Pd/Ni ratios were synthesized by seed-mediated growth strategy. Pd-Ni NP-3 NPs outperformed other Pd-based catalysts in FOR activity (∼28676 mA/mgPd). This enhancement resulted from the component-dependent effects, which modulate the Pd(0) and Ni(OH)2 species, and resulting in an optimal balance of effective active sites and anti-poisoning ability.

CuFe2O4 spinel synergize with Pd as a robust electrocatalyst for formate oxidation reaction

As an energy conversion device, direct formate fuel cell (DFFC) has attracted much attention due totheir security, affordability as well as high energy conversion efficiency. However, the whole performance of the DFFC is unsatisfactory because of the repaid activity loss induced by Hads-poisoning of anode Pd catalysts during the formate oxidation reaction (FOR). Herein, we induced a CuFe2O4 complex into Pd to enhance the activity and release the Hads-poisoning to prolong the durability. The results reflect that the *OH generation capacity of CuFe2O4 played an important role in the Hads-stripping (Pd-Hads + CuFe2O4-OHads → Pd + CuFe2O4 + H2O). After optimized PCFO-3 (Pd/CuFe2O4) not only show a super FOR activity of 4427 mA mgPd−1 mass activity and 243 mA cm−2 specific activity, but also show a novel cycle durability of 10,000 times CV cycles and 12 h long-term i-t operation with a termination activity of 26.95 mA mgPd−1. More interestingly, this PCFO-3 shows a self-adapting process which induced an activity enhancement of 27.6% due to the synergistic effect of CuFe2O4 and Pd. We believe this work paves a new avenue for matching counterparts to enhance the FOR activity and durability of Pd electro-catalysts cooperatively.

Bifunctional PdPt bimetallenes for formate oxidation‐boosted water electrolysis

AbstractSmall‐molecule electrooxidation‐boosted water electrolysis (WE) is an energy‐saving method for hydrogen (H2) production. Herein, PdPt bimetallenes (PdPt BMLs) are obtained through the simple galvanic replacement reaction. PdPt BMLs reveal 2.93‐fold enhancement in intrinsic electroactivity and 4.53‐fold enhancement in mass electroactivity for the formate oxidation reaction (FOR) with respect to Pd metallenes (Pd MLs) at 0.50 V potential due to the synergistic effect. Meanwhile, the introduction of Pt atoms also considerably increases the electroactivity of PdPt BMLs for hydrogen evolution reaction (HER) with respect to Pd MLs in an alkaline medium, which even exceeds that with the use of commercial Pt nanocrystals. Inspired by the outstanding FOR and HER electroactivity of bifunctional PdPt BMLs, a two‐electrode FOR‐boosted WE system (FOR‐WE) is constructed by using PdPt BMLs as the cathode and the anode. The FOR‐WE system only requires an operational voltage of 0.31 V to achieve H2 production, which is 1.48 V lower than that (ca. 1.79 V) with the use of the traditional WE system.

Ultrathin PdCu Nanosheet as Bifunctional Electrocatalysts for Formate Oxidation Reaction and Oxygen Reduction Reaction.

The development of robust nonplatinum electrocatalysts to enhance the performance of formate oxidation reaction (FOR) and oxygen reduction reaction (ORR) is one of the key issues for the commercialization of direct formate fuel cells (DFFCs), but still challenging. Herein, a structurally controlled 3D flower-like PdCu nanosheet (NS) catalyst is synthesized by a method of oil bath reduction under mild conditions as a bifunctional electrocatalyst for DFFCs. Under the dual tuning on the composition and intermetallic phase, the PdCu nanosheet catalyst exhibits 8.67 times higher mass activity for anodic formate oxidation reaction than the commercial Pd/C. For the cathodic ORR, a positive shift half-wave potential is obtained for PdCu nanosheets exceeding Pt/C. Moreover, after a long-term stability test, the current density of the PdCu nanosheet catalyst for FOR and ORR can be well maintained with the least activity decay. When the PdCu NSs are used as optimized anode and cathode electrodes for DFFCs enable a peak power density as high as 53 mW cm-2 at room temperature, which is about 1.3 times higher than that of the commercial Pd/C and Pt/C as anode and cathode electrodes. This work provides a potential strategy to improve the catalytic performance of non-Pt-based nanocatalysts.

Phosphorous incorporation into palladium tin nanoparticles for the electrocatalytic formate oxidation reaction

The deployment of direct formate fuel cells (DFFCs) relies on the development of active and stable catalysts for the formate oxidation reaction (FOR). Palladium, providing effective full oxidation of formate to CO2, has been widely used as FOR catalyst, but it suffers from low stability, moderate activity, and high cost. Herein, we detail a colloidal synthesis route for the incorporation of P on Pd2Sn nanoparticles. These nanoparticles are dispersed on carbon black and the obtained composite is used as electrocatalytic material for the FOR. The Pd2Sn0.8P-based electrodes present outstanding catalytic activities with record mass current densities up to 10.0 A mgPd-1, well above those of Pd1.6Sn/C reference electrode. These high current densities are further enhanced by increasing the temperature from 25 °C to 40 °C. The Pd2Sn0.8P electrode also allows for slowing down the rapid current decay that generally happens during operation and can be rapidly re-activated through potential cycling. The excellent catalytic performance obtained is rationalized using density functional theory (DFT) calculations.

Regulation of the Work Function Difference Promotes In Situ Phase Transition of WO3-x for Efficient Formate Electrooxidation.

Direct formate fuel cells (DFFCs) have drawn tremendous attention because they are environmentally benign and have good safety. However, the lack of advanced catalysts for formate electrooxidation hinders the development and applications of DFFCs. Herein, we report a strategy of regulating the metal-substrate work function difference to effectively promote the transfer of adsorbed hydrogen (Had), thus enhancing formate electrooxidation in alkaline solutions. By introducing rich oxygen vacancies, the obtained catalysts of Pd/WO3-x-R show outstanding formate electrooxidation activity, exhibiting an extremely high peak current of 15.50 mA cm-2 with a lower peak potential of 0.63 V. In situ electrochemical Fourier transform infrared and in situ Raman measurements verify an enhanced in situ phase transition from WO3-x to HxWO3-x during the formate oxidation reaction process over the Pd/WO3-x-R catalyst. The results of experimental and density functional theory (DFT) calculations confirm that the work function difference (ΔΦ) between the metal (Pd) and substrate (WO3-x) would be regulated by inducing oxygen vacancies in the substrate, resulting in improved hydrogen spillover at the interface of the catalyst, which is essentially responsible for the observed high performance of formate oxidation. Our findings provide a novel strategy of rationally designing efficient formate electrooxidation catalysts.

Tensile strained PdNi bimetallene for energy-efficient hydrogen production integrated with formate oxidation

Strain engineering is a prospective approach to enhance catalytic performance of electrocatalysts. Herein, we report a CO-confined growth method for the synthesis of tensile-strained PdNi bimetallene as bifunctional catalyst for hydrogen evolution reaction (HER) and formate oxidation reaction (FOR). Ascribed to electronic effect and strain effect derived from the introduction of Ni and ultrathin curved geometry, PdNi bimetallene possesses sufficient active sites and modulates the adsorption/dissociation of electrocatalytic intermediates, resulting in outstanding activity and stability for HER and FOR. In HER-FOR system, a low cell voltage of 0.51 V is achieved at 20 mA cm−2 by PdNi bimetallene, which is 1.21 V lower than that for the conventional water electrolysis. This work offers a versatile route for the synthesis of crimped bimetallene materials for advanced energy-efficient hydrogen production and beyond.

Studies on the catalytic mechanism of formate dehydrogenase from Candida boidinii using isotope-labelled substrate and co-enzyme

Formate dehydrogenase from Candida boidinii (CbFDH; EC.1.2.1.2) catalyses the formate oxidation and the CO2 reduction using the redox pair of NAD+/NADH as a co-enzyme. Isotope substitution of substrate is a means of addressing the participation of protein motions in biocatalytic reactions. The effects of isotope-labelled NAD+ (NAD+-d4) and deuterium or 13C-labelled-formate (DCOO- or H13COO-) on CbFDH-catalyzed formate oxidation activity were investigated. By using DCOO- as a substrate, the isotope effect was exhibited in the process of CbFDH-catalyzed formate oxidation and the reaction rate was reduced by 38 % compared to the system using non-isotope-labelled formate. Moreover, the isotope effect also was strongly exhibited using both of NAD+-d4 and DCOO- in the formate oxidation with CbFDH and the reaction rate was reduced by 28 % compared to the system using non-isotope-labelled NAD+ and formate. On the other hand, it was clarified that there is no significantly affect the formate oxidation reaction catalyzed by CbFDH using 13C-labeled formate as a substrate. From these results, it was suggested that C-H bond cleavage of formate and nucleophilic attack of hydrogen on NAD+ dominate the reaction rate in CbFDH-catalyzed formate oxidation. In addition, the hydrogen bonds formed between formate, NAD+ and water molecules in the substrate binding site of CbFDH was also important in the formate oxidation to CO2.

Ultrafine Pd@PdPt nanowires with a single-atom alloy shell for efficient formate oxidation

Ultrafine Pd@PdPt nanowires with a Pd–Pt single atom alloy shell achieve significantly enhanced electrocatalytic performance towards the formate oxidation reaction.

Reconstruction of an AgPd nanoalloy with oxidation for formate oxidation electrocatalysis

AgPd–Ag2O and AgPd–AgF heterointerfaces are prepared through reconstruction and designed by using “2D materials on metal” heterostructure models to illustrate their impact mechanism on electrocatalytic activity toward the formate oxidation reaction.

The Synergic Effects of Trimetallic Pdcuin Nanoparticles in Ethanol and Formate Oxidation Reaction for Remarkable Catalytic Performance

The Synergic Effects of Trimetallic Pdcuin Nanoparticles in Ethanol and Formate Oxidation Reaction for Remarkable Catalytic Performance