PdCu@Pd Nanocube with Pt-like Activity for Hydrogen Evolution Reaction

Electroreduction-driven distorted nanotwins activate pure Cu for efficient hydrogen evolution

Precious metals such as Pt are favoured as catalysts for the hydrogen evolution reaction (HER) due to their excellent catalytic activity. However, the scarcity and high cost of precious metals have prompted researchers to explore cheaper alternatives such as Cu. Nevertheless, Cu shows poor catalytic performance due to weak binding with intermediates. Here the catalytic activity of pure Cu is activated via electroreduction-driven modification of the local structure, achieving a HER catalytic performance superior to commercial Pt/C catalysts for working current densities greater than 100 mA cm-2 in acid electrolyte. Activation involved two steps. First, polycrystalline Cu2O nanoparticles were prepared via pulsed laser ablation, resulting in grain boundaries within the Cu2O particles as observed using electron microscopy. Next, the Cu2O particles were electroreduced to pure Cu, inducing the formation of distorted nanotwins and edge dislocations. These local structures induce high lattice strain and decrease the Cu coordination number, enhancing the interaction between Cu and intermediates-as calculated using density functional theory-leading to the excellent catalytic activity and durability of the catalyst. Our observations show that low-cost pure Cu can be a promising HER catalyst for large-scale industrial applications.

Synergistic Electronic Interaction in PdCu Alloy/TiO2-NSs for Ambient Efficient Dehydrogenation of Formic Acid

Palladium-based catalysts are remarkable in endorsing hydrogen (H2) generation through formic acid (HCOOH, FA) dehydrogenation under near-ambient conditions. Hydrogen energy efficiency depends on high-performance catalyst design. In this study, Pd-Cu nanoalloy catalysts with mutable atomic ratios are successfully fabricated on TiO2 nanosheets (TiO2-NSs).The synergistic electronic interactions between Palladium (Pd) and copper (Cu) are revealed through a density of states (DOS) analysis of alloy supported over a mixed valence state of Ti linked to oxygen vacancies (Vo) in TiO2-NSs, Enhanced adsorption of target molecules reveals novel active sites for Formic acid dehydrogenation (FAD), with O─H bond cleavage via HCOO formate intermediate preceding C─H and C─O bond cleavage. Experimental and theoretical research demonstrates that the Pd-Cu/TiO2-NSs (3:7) catalyst d electron redistribution and d-band center shift lower the activation energy for O─H bond cleavage, exhibit superior H2 production than pure Pd and Cu, increasing Pd electron density due to synergistic effects from reactive crystal facets, defects, and strong metal support interactions (SMSI), lowering the activation energy for HCOOH dissociation step, generating carbon dioxide (CO2) and H2 with a unprecedented high turnover frequency (TOF) of 6268 molH2.h-1.molPd-1 at 303K with activation energy (Ea) of 15 KJ mol-1. This attempt models an efficient HCOOH-to-hydrogen catalyst.

Solvothermal synthesis of PdCu nanorings with high catalytic performance for alcohol electrooxidation

Two-dimensional (2D) Pd-based nanostructures with a high active surface area and a large number of active sites are commonly used in alcohol oxidation research, whereas the less explored ring structure made of nanosheets with large pores is of interest. In this study, we detail the fabrication of PdCu nanorings (NRs) featuring hollow interiors and low coordinated sites using a straightforward solvothermal approach. Due to increased exposure of active sites and the synergistic effects of bimetallics, the PdCu NRs exhibited superior catalytic performance in both the ethanol oxidation reaction (EOR) and the ethylene glycol oxidation reaction (EGOR). The mass activities of PdCu NRs for EOR and EGOR were measured at 7.05 A/mg and 8.12 A/mg, respectively, surpassing those of commercial Pd/C. Furthermore, the PdCu NRs demonstrated enhanced catalytic stability, maintaining higher mass activity levels compared to other catalysts during stability testing. This research offers valuable insights for the development of efficient catalysts for alcohol oxidation.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite derived from lignin: an efficient peroxymonosulfate activator for naphthalene degradation

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite (Fe-Cu-N-PC) was prepared via direct pyrolysis by employing black liquor lignin as a main precursor, and it was utilized as a novel catalyst for PMS activation in degrading naphthalene. Under the optimum experimental conditions, the naphthalene degradation rate was up to 93.2% within 60 min in the Fe-Cu-N-PC/PMS system. The porous carbon framework of Fe-Cu-N-PC could facilitate the quick molecule diffusion of reactants towards the inner bimetallic nanoparticles and enriched naphthalene molecules from the solution by a specific adsorption, which increased the odds of contact between naphthalene and reactive oxygen species and improved the reaction efficiency. The quenching reaction proved that the non-free radical pathway dominated by 1O2 was the main way in naphthalene degradation, while the free radical pathway involving SO4·- and ·OH only played a secondary role. Moreover, owing to its high magnetization performance, Fe-Cu-N-PC could be magnetically recovered and maintained excellent naphthalene degradation rate after four degradation cycles. This research will offer a theoretical basis for the construction of facile, efficient, and green technologies to remediate persistent organic pollutants in the environment.

Exploring the synergistic effect of palladium nanoparticles and highly dispersed transition metals on carbon nitride/super-activated carbon composites for boosting electrocatalytic activity

In the present work, multifunctional electrocatalysts formed by palladium nanoparticles (Pd NPs) loaded on Fe or Cu-containing composite supports, based on carbon nitride (C3N4) and super-activated carbon with a high porosity development (SBET 3180 m2/g, VDR 1.57 cm3/g, and VT 1.65 cm3/g), were synthesised. The presence of Fe or Cu sites favoured the formation of Pd NPs with small average particle size and a very narrow size distribution, which agreed with Density Functional Theory (DFT) calculations showing that the interaction of Pd clusters with C3N4 flakes is weaker than with Cu- or Fe-C3N4 sites. The electroactivity was also dependent on the composition and, as suggested by preliminary DFT calculations, the Pd-Cu catalyst showed lower overpotential for hydrogen evolution reaction (HER) while bifunctional oxygen reduction reaction/ oxygen evolution reaction (ORR/OER) behaviour was superior in Pd-Fe sample. The Pd-Fe electrocatalyst was studied in a zinc-air battery (ZAB) for 10 h, showing a performance similar to a commercial Pt/C + RuO2 catalyst with a high content of precious metal. This study demonstrates the synergistic effect between Pd species and transition metals and shows that transition metals anchored on C3N4-based composite materials promote the electroactivity of Pd NPs in HER, ORR and OER due to the interaction between both species.

Laser-Synthesized Ru-Anchored Few-Layer Black Phosphorus for Superior Hydrogen Evolution: Role of Acoustic Levitation

Electrochemical water splitting, driven by processed catalysts, is the most reasonable method for hydrogen production. This study demonstrates an activation phenomenon with ruthenium (Ru) nanoclusters on few-layered black phosphorus (BP), greatly enhancing the electrocatalytic hydrogen evolution reaction (HER). Efficient BP exfoliation was achieved using acoustic levitators and pulsed laser irradiation in liquids (PLIL), yielding charge-transfer Ru-nanoclusters on modulated surfaces. Various PLIL parameters were examined for the optimal BP sheet size. After ruthenization, Ru's d-band center facilitated hydrogen adsorption via Ru-H bonding. Synergy between BP's charge-carrier properties and Ru's active sites boosted HER kinetics with an ultralow overpotential of 84 mV at 10 mA/cm2 in KOH. Additionally, the RuO2 || RuBP-2 electrolyzer demonstrated remarkable overall water splitting performance at ∼1.60 V at 10 mA/cm2. These results highlight the pivotal role of metal nanoclusters on exfoliated BP surfaces and offer a refined strategy for high-density electrocatalysts in energy conversion.

An In Situ Fabricated Hydrogel Polymer - Palladium Nanocomposite Electrocatalyst for the HER: Critical Role of the Polymer in Realizing High Efficiency and Stability

Development of general and simple designs of catalytic electrodes for the hydrogen evolution reaction (HER) is critical. The present work demonstrates the multiple roles played by a hydrogel polymer in the fabrication and activity enhancement of the nanoelectrocatalyst. A nanocomposite thin film of Pd with the insulating hydrogel, poly(2-hydroxyethyl methacrylate) (PHEMA), is fabricated through a facile in situ process, the polymer itself functioning as the reducing/stabilizing agent in the formation of Pd nanoparticles. Pd-PHEMA on Ni foam enables efficient HER in alkaline medium with a low overpotential; the polymer enables the electrocatalysis by its swelling and confinement of the electrolyte. Most significantly, when the electrode is subjected to an optimized cycling protocol, the overpotential decreases steadily, reaching an impressively low value of 36 mV (@10 mA cm-2 ). A low Tafel slope (68 mV dec-1 ), high exchange current density, Faradaic efficiency and TOF (3.27 mA cm-2 , 99 %, 122.7 h-1 ), and extended stability are achieved. Detailed investigations reveal the active role of the polymer in the evolution of the nanocatalyst, itself undergoing favorable morphological changes. The study illustrates the widened scope for developing efficient and stable catalytic electrodes with hydrogel polymers and unique features that promote the generation of green hydrogen.

Formation of intermetallic PdIn nanoparticles: influence of surfactants on nanoparticle atomic structure

Bimetallic nanoparticles have been extensively studied as electrocatalysts due to their superior catalytic activity and selectivity compared to their monometallic counterparts. The properties of bimetallic materials depend on the ordering of the metals in the structure, and to tailor-make materials for specific applications, it is important to be able to control the atomic structure of the materials during synthesis. Here, we study the formation of bimetallic palladium indium nanoparticles to understand how the synthesis parameters and additives used influence the atomic structure of the obtained product. Specifically, we investigate a colloidal synthesis, where oleylamine was used as the main solvent while the effect of two surfactants, oleic acid (OA) and trioctylphosphine (TOP) was studied. We found that without TOP included in the synthesis, a Pd-rich intermetallic phase with the Pd3In structure initially formed, which transformed into large NPs of the CsCl-structured PdIn phase. When TOP was included, the syntheses yielded both In2O3 and Pd3In. In situ X-ray total scattering with Pair Distribution Function analysis was used to study the formation process of PdIn bimetallic NPs. Our results highlight how seemingly subtle changes to material synthesis methods can have a large influence on the product atomic structure.

Octahedral Pd3Cu7 Catalysts on Diverse Support Materials for Efficient Hydrogen Evolution: Theoretical Investigation and Mechanistic Perspective

This work showcases a novel strategy for the synthesis of shape-dependent alloy nanostructures with the incorporation of solid substrates, leading to remarkable enhancements in the electrocatalytic performance. Herein, an aqueous medium approach has been used to synthesize an octahedral PdXCuY alloy of different Pd:Cu ratios to better comprehend their electrocatalytic potential. With the aim to outperform high activity and efficient stability, zirconium oxide (ZrO2), graphene oxide nanosheets (GONs), and hexagonal boron nitride nanosheets (hBNNs) solid substrates are occupied to decorate the optimized Pd3Cu7 catalyst with a minimum 5 wt % metal loading. When compared to the counterparts and different ratios, the Pd3Cu7@hBNNs catalyst exhibited an optimal activity for hydrogen evolution reaction (HER). The lower overpotential and Tafel values observed are 64 and 51 mV/dec for Pd3Cu7@hBNNs followed by Pd3Cu7@ZrO2, which showed a 171 mV overpotential and a 98 mV/dec Tafel value, respectively. Meanwhile, the Pd3Cu7@GONs were found to have a 202 mV overpotential and a 110 mV/dec Tafel value. The density functional theory, which achieves a lower free energy (ΔGH*) value for Pd3Cu7@hBNNs than the other catalysts for HER, further supports its excellent performance in achieving the Volmer-Heyrovsky mechanism path. Moreover, the superior HER activity and sturdier resilience after 8 h of stability may be due to the synergy between the metal atoms, monodisperse decoration, and the coordination effect of the support material.

Bimetallic Nanoalloy Catalysts for Green Energy Production: Advances in Synthesis Routes and Characterization Techniques

Bimetallic Nanoalloy catalysts have diverse uses in clean energy, sensing, catalysis, biomedicine, and energy storage, with some supported and unsupported catalysts. Conventional synthetic methods for producing bimetallic alloy nanoparticles often produce unalloyed and bulky particles that do not exhibit desired characteristics. Alloys, when prepared with advanced nanoscale methods, give higher surface area, activity, and selectivity than individual metals due to changes in their electronic properties and reduced size. This review demonstrates the synthesis methods and principles to produce and characterize highly dispersed, well-alloyed bimetallic nanoalloy particles in relatively simple, effective, and generalized approaches and the overall existence of conventional synthetic methods with modifications to prepare bimetallic alloy catalysts. The basic concepts and mechanistic understanding are represented with purposely selected examples. Herein, the enthralling properties with widespread applications of nanoalloy catalysts in heterogeneous catalysis are also presented, especially for Hydrogen Evolution Reaction (HER), Oxidation Reduction Reaction (ORR), Oxygen Evolution Reaction (OER), and alcohol oxidation with a particular focus on Pt and Pd-based bimetallic nanoalloys and their numerous fields of applications. The high entropy alloy is described as a complicated subject with an emphasis on laser-based green synthesis of nanoparticles and, in conclusion, the forecasts and contemporary challenges for the controlled synthesis of nanoalloys are addressed.

Nanocomposite Electrocatalysts for Hydrogen Evolution Reactions (HERs) for Sustainable and Efficient Hydrogen Energy-Future Prospects

Hydrogen is considered a good clean and renewable energy substitute for fossil fuels. The major obstacle facing hydrogen energy is its efficacy in meeting its commercial-scale demand. One of the most promising pathways for efficient hydrogen production is through water-splitting electrolysis. This requires the development of active, stable, and low-cost catalysts or electrocatalysts to achieve optimized electrocatalytic hydrogen production from water splitting. The objective of this review is to survey the activity, stability, and efficiency of various electrocatalysts involved in water splitting. The status quo of noble-metal- and non-noble-metal-based nano-electrocatalysts has been specifically discussed. Various composites and nanocomposite electrocatalysts that have significantly impacted electrocatalytic HERs have been discussed. New strategies and insights in exploring nanocomposite-based electrocatalysts and utilizing other new age nanomaterial options that will profoundly enhance the electrocatalytic activity and stability of HERs have been highlighted. Recommendations on future directions and deliberations for extrapolating information have been projected.

Ethanol Oxidation via 12-Electron Pathway on Spiky Au@AuPd Nanoparticles Assisted by Near-Infrared Light

In this work, ethanol oxidation reaction (EOR) via 12-electron (C1-12e) pathway on spiky Au@AuPd nanoparticles (NPs) with ultrathin AuPd alloy shells is achieved in alkaline media with the assistance of the near-infrared (NIR) light. It is found that OH radicals can be produced from the OH_ads species adsorbed on the surfaces of Pd atoms led by surface plasmon resonance (SPR) effect of spiky Au@AuPd NPs under the irradiation of NIR light. Moreover, OH radicals play the key role for the achievement of EOR proceeded by the desirable C1-12e pathway because OH radicals can directly break the C-C bonds of ethanol. Accordingly, the electrocatalytic performance of spiky Au@AuPd NPs toward EOR under NIR light is greatly improved. For instance, their mass activity can be up to 33.2 A mg_pd ^-1 in the 0.5 m KOH solution containing 0.5 m ethanol, which is about 158 times higher than that of commercial Pd/C catalysts (0.21 A mg_pd ^-1 ) and is better than those of the state-of-the-art Pd-based catalysts reported in literature thus far, to the best of our knowledge. Moreover, their highest mass activity can be further improved to 118.3 A mg_pd ^-1 in the 1.5 m KOH solution containing 1.25 m ethanol.

Tuning crystal-phase of bimetallic single-nanoparticle for catalytic hydrogenation

Bimetallic nanoparticles afford geometric variation and electron redistribution via strong metal-metal interactions that substantially promote the activity and selectivity in catalysis. Quantitatively describing the atomic configuration of the catalytically active sites, however, is experimentally challenged by the averaging ensemble effect that is caused by the interplay between particle size and crystal-phase at elevated temperatures and under reactive gases. Here, we report that the intrinsic activity of the body-centered cubic PdCu nanoparticle, for acetylene hydrogenation, is one order of magnitude greater than that of the face-centered cubic one. This finding is based on precisely identifying the atomic structures of the active sites over the same-sized but crystal-phase-varied single-particles. The densely-populated Pd-Cu bond on the chemically ordered nanoparticle possesses isolated Pd site with a lower coordination number and a high-lying valence d-band center, and thus greatly expedites the dissociation of H2 over Pd atom and efficiently accommodates the activated H atoms on the particle top/subsurfaces.

Nanoengineering of Catalysts for Enhanced Hydrogen Production

Hydrogen (H2) has emerged as a sustainable energy carrier capable of replacing/complementing the global carbon-based energy matrix. Although studies in this area have often focused on the fundamental understanding of catalytic processes and the demonstration of their activities towards different strategies, much effort is still needed to develop high-performance technologies and advanced materials to accomplish widespread utilization. The main goal of this review is to discuss the recent contributions in the H2 production field by employing nanomaterials with well-defined and controllable physicochemical features. Nanoengineering approaches at the sub-nano or atomic scale are especially interesting, as they allow us to unravel how activity varies as a function of these parameters (shape, size, composition, structure, electronic, and support interaction) and obtain insights into structure–performance relationships in the field of H2 production, allowing not only the optimization of performances but also enabling the rational design of nanocatalysts with desired activities and selectivity for H2 production. Herein, we start with a brief description of preparing such materials, emphasizing the importance of accomplishing the physicochemical control of nanostructures. The review finally culminates in the leading technologies for H2 production, identifying the promising applications of controlled nanomaterials.

A ternary PdNiMo alloy as a bifunctional nanocatalyst for the oxygen reduction reaction and hydrogen evolution reaction

Mo0.2Pd3Ni/NC shows superior electrochemical performances for both ORR and HER due to the charge redistribution among Ni, Pd, and Mo, tuning the electronic structure of Pd.

Palladium Nanoparticles Hardwired in Carbon Nanoreactors Enable Continually Increasing Electrocatalytic Activity During the Hydrogen Evolution Reaction

Catalysts typically lose effectiveness during operation, with much effort invested in stabilising active metal centres to prolong their functional lifetime for as long as possible. In this study palladium nanoparticles (PdNP) supported inside hollow graphitised carbon nanofibers (GNF), designated as PdNP@GNF, opposed this trend. PdNP@GNF exhibited continuously increasing activity over 30000 reaction cycles when used as an electrocatalyst in the hydrogen evolution reaction (HER). The activity of PdNP@GNF, expressed as the exchange current density, was always higher than activated carbon (Pd/C), and after 10000 cycles PdNP@GNF surpassed the activity of platinum on carbon (Pt/C). The extraordinary durability and self-improving behaviour of PdNP@GNF was solely related the unique nature of the location of the palladium nanoparticles, that is, at the graphitic step-edges within the GNF. Transmission electron microscopy imaging combined with spectroscopic analysis revealed an orchestrated series of reactions occurring at the graphitic step-edges during electrocatalytic cycling, in which some of the curved graphitic surfaces opened up to form a stack of graphene layers bonding directly with Pd atoms through Pd-C bonds. This resulted in the active metal centres becoming effectively hardwired into the electrically conducting nanoreactors (GNF), enabling facile charge transport to/from the catalytic centres resulting in the dramatic self-improving characteristics of the electrocatalyst.

Phase-Controlled Synthesis of Pd-Sn Nanocrystal Catalysts of Defined Size and Shape

Bimetallic Pd-based nanoparticles (NPs) are of interest as electrocatalysts for formic acid electrooxidation (FAEO) because of their higher initial catalytic activity and CO tolerance when compared to Pt. Intermetallic NPs (i-NPs) with specific geometric and electronic structures generally exhibit superior catalytic activity, selectivity, and durability when compared to their disordered (random alloy) counterparts; however, the colloidal synthesis of i-NPs remains a challenge. Here, a one-pot method was demonstrated as a facile route to obtain monodisperse Pd-Sn NPs with phase control, including intermetallic hexagonal Pd3Sn2 (P63/mmc), intermetallic orthorhombic Pd2Sn (Pnma), and alloy cubic Pd3Sn (FCC, Fm3m) as size-controlled NPs with quasi-spherical shapes. Initial metal precursor ratios and reaction temperature were critical parameters to achieving phase control. Also, slight modifications of synthetic conditions resulted in either Pd2Sn nanorhombohedra or nanorods with tunable aspect ratios. A systematic evaluation of the Pd-Sn NPs for FAEO showed that most presented higher specific activities when compared to commercial Pd/C, in which Pd2Sn quasi-spheres and nanorhombohedra showed the highest catalytic activity for FAEO. These results highlight the benefits of phase-controlled Pd-based nanocatalysts with defined nanocrystal size and shape, with use of trioctylphospine (TOP) and oleic acid (OA) central to shape and size control.

Bidirectional controlling synthesis of branched PdCu nanoalloys for efficient and robust formic acid oxidation electrocatalysis

Through a two-way control of hexadecyl trimethyl ammonium bromide (CTAB) and hydrochloric acid (HCl), the PdCu nanoalloys with branched structures are synthesized in one step by hydrothermal reduction and used as electrocatalysts for formic acid oxidation reaction (FAOR). In this two-way control strategy, the CTAB is used as a structure-oriented surfactant, while a certain amount of HCl is used to control the reaction kinetics for achieving gradual growth of multi-dendritic structures. The characterizations including scanning transmission electron microscope (STEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) suggest that PdCu nanoalloys with unique multi-dendritic branches have favorable electronic structure and lattice strain for electrocatalyzing the oxidation of formic acid. In specific, among the electrocatalysts with different Pd/Cu ratios, the Pd₁Cu₁ branched nanoalloys have the largest electrochemically active surface area (ECSA) and the best performance for the FAOR. The catalytic activity of the Pd₁Cu₁ branched nanoalloys is 2.4 times that of commercial Pd black. After the chronoamperometry test, the Pd₁Cu₁ branched nanoalloys still maintain their original morphologies and higher current density than that of the commercial Pd black. In addition, in the CO-stripping tests, the initial oxidation potential and the oxidation peak potential of the PdCu branched nanoalloys for CO adsorption are lower than those of commercial Pd balck, evincing their better anti-poisoning performance.

Applications of bimetallic PdCu catalysts

Bimetallic PdCu nanoparticles can be applied as catalysts in a wide range of chemical and electrochemical reactions.

Assembly of Bimetallic PdAg Nanosheets and Their Enhanced Electrocatalytic Activity toward Ethanol Oxidation

The direct ethanol fuel cells in an alkaline medium have a broad vision of applications because of their large energy density, reasonable power density, and environmentally friendly features. Herein, we present a facile one-step method to synthesize PdAg nanosheet assemblies (NSAs) in a mixed solution of N,N-dimethylformamide and water with the addition of molybdenum hexacarbonyl and cetyltrimethylammonium bromide. Pure Pd NSA shows an irregular shape while PdAg NSAs gradually undergo a process from solid assembly to a hollow structure with the Pd/Ag molar ratio changing from 3:1 to 2:1 to 1:1. The formation of alloy nanosheets in the assemblies combined with the introduction of Ag in the Pd catalyst enhances the catalytic activity toward ethanol electrooxidation from 1524 mA mg^-1 of pure Pd NSA to 1866 mA mg^-1 of PdAg NSA with a Pd/Ag molar ratio of 2:1. On the basis of the experimental data, compared with pure Pd structures, both the nature of a thin nanosheet of PdAg NSAs and the structural changes in the alloy assemblies play key roles in determining the electrocatalytic activity of these Pd-based catalysts.

Intermetallic Pd3Pb nanocubes with high selectivity for the 4-electron oxygen reduction reaction pathway

Pd-Based nanoparticles are excellent alternatives to the typically used Pt-based materials that catalyze fuel cell reactions. Specifically, Pd-based intermetallic nanomaterials have shown great promise as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline media; however, their synthesis remains a challenge and shape-controlled nanoparticles are limited. Here, a low-temperature approach to intermetallic Pd₃Pb nanocubes is demonstrated and their electrocatalytic properties evaluated for the ORR. The intermetallic Pd₃Pb nanocubes outperformed all reference catalysts, with a mass activity of 154 mA mg_Pd^-1 which is a 130% increase in activity compared to the commercial Pd/C reference and a 230% increase compared to Pd nanocubes. Tafel analysis reveals that the Pd₃Pb nanocubes are highly selective for the 4-electron reduction pathway, with minimal HO₂^- formation. Density functional theory (DFT) calculations show that the increased activity for the intermetallic nanocubes compared to Pd is likely due to the weakening of OH* adsorption, decreasing the required overpotential. These results show that intermetallic Pd₃Pb nanocubes are highly efficient for the 4-electron pathway of the ORR and could inspire the study of other shape-controlled intermetallics as catalysts for fuel cell applications.

Interface Nanoengineering of PdNi-S/C Nanowires by Sulfite-Induced for Enhancing Electrocatalytic Hydrogen Evolution

The interfacial structural design of materials in nanoscale is a promising approach to regulate the physicochemical properties of materials and further optimize material properties for a variety of potential applications. Herein, PdNi-S/C nanowires with inductive sulfite has been successfully crafted through hydrothermal synthesis and applied as a superior hydrogen evolution reaction (HER) catalyst. Based on the autocatalytic mechanism, PdNi alloy nanoparticles were synthesized by controlling reduction kinetics with the presence of formic acid. Meanwhile, the sulfite is selected as an effective inductive agent to form PdNi-S/C nanowires with amorphous interfaces. The morphology, composition, and electronic structure of the synthesized PdNi-S/C were studied in detail. The PdNi-S/C manifests excellent HER performance in alkaline solution with an overpotentials of 67 mV at current density of 10 mA cm^-2, a Tafel slope of 69.4 mV dec^-1, and significantly long-term durability. The improvement of HER performance of the PdNi-S/C is attributed to the one-dimensional nanowire structure, abundant sulfur vacancies and defects, and the synergistic effect between PdNi-S nanowires with the graphite carbon. Furthermore, this present work offers a novel method for structure adjustment of materials to effectively control their property and catalytic performance.

General Strategy to Optimize Gas Evolution Reaction via Assembled Striped-Pattern Superlattices

Redesigning heterogeneous catalysts so that they can simultaneously integrate the efficiency and durability under reaction environments with respect to gas fuel production, such as hydrogen (H₂), oxygen (O₂), or carbon monoxide (CO), has proven challenging. In this work, we report the successful template-assisted printing-based assembly of platinum (Pt) nanoparticles (NPs) into striped-pattern (SP) superlattices to produce H₂. In comparison to drop-casting flat Pt NPs films, SP superlattices lead to higher mass transference and smaller bubble stretch force, representing a general strategy to improve the efficiency and durability of pre-existed Pt catalysts for the hydrogen evolution reaction (HER), as well as higher current densities than commercial Pt/C, Pt NP films, and many of the other Pt-based or non-Pt-based HER catalysts reported in the literature. The generic nature of template-assisted printing leads to flexibility in the composition, size, and shape of the constituent NPs or molecules, and thus extends such an accelerated technique for producing the oxygen evolution reaction and electrochemical reduction of CO₂ to CO.

PtNixCoy concave nanocubes: synthesis and application in photocatalytic hydrogen generation

PtNi_xCo_y alloy concave nanocubes coupled with CdS nanorods were applied in the H₂ evolution reaction under visible light irradiation.

Direct deposition of a nanoporous palladium electrocatalyst for efficient hydrogen evolution reaction

The porous palladium directly deposited on metallic substrates by aerosol-assisted chemical vapor deposition exhibits remarkable HER performance in an acidic electrolyte.

Strongly Coupled Interface Structure in CoFe/Co3 O4 Nanohybrids as Efficient Oxygen Evolution Reaction Catalysts

The quest for developing electrochemical energy-storage and -conversion technologies continues to be a great impetus to develop cost-effective, highly active, and electrochemically stable electrocatalysts for overcoming the activation energy barriers of the oxygen evolution reaction (OER). Co₃ O₄ nanocrystals have great potential as OER catalysts, and research efforts on improving the catalytic activity of Co₃ O₄ are currently underway in many laboratories. Herein, CoFe layered double hydroxide (LDH) nanosheets were directly grown on the active Co₃ O₄ substrate to form nanohybrid electrocatalysts for OER. The CoFe LDH/Co₃ O₄ (6:4) nanohybrid exhibited superior catalytic performance with a low overpotential and a small Tafel slope in alkaline solution. The outstanding performance of the CoFe LDH/Co₃ O₄ (6:4) nanohybrid was primarily owing to the synergistic effects induced by the strongly coupled interface between CoFe LDH and Co₃ O₄ ; this feature enhanced the intrinsic OER catalytic activity of the nanohybrid and favored fast charge transfer. Compared with other Co₃ O₄ -based catalysts, the nanohybrid shows advantages and offers a feasible avenue for improving the activity of Co₃ O₄ -based catalysts.

Ruthenium@N-doped graphite carbon derived from carbon foam for efficient hydrogen evolution reaction

Ru nanoparticles doped in carbon foam were encapsulated in nitrogen-doped graphite carbon materials (Ru-NGC). The resultant Ru-NGC possesses superior hydrogen evolution activity with a small onset potential of 9.5 mV and excellent durability due to the optimized Ru electronic state in nitrogen-doped graphite.

Shaping well-defined noble-metal-based nanostructures for fabricating high-performance electrocatalysts: advances and perspectives

This review highlights recent advances in shaping protocols and structure-activity relationships of noble-metal-based catalysts with well-defined nanostructures in electrochemical reactions.

Carbon-Quantum-Dots-Loaded Ruthenium Nanoparticles as an Efficient Electrocatalyst for Hydrogen Production in Alkaline Media

Highly active, stable, and cheap Pt-free catalysts for the hydrogen evolution reaction (HER) are facing increasing demand as a result of their potential use in future energy-conversion systems. However, the development of HER electrocatalysts with Pt-like or even superior activity, in particular ones that can function under alkaline conditions, remains a significant challenge. Here, the synthesis of a novel carbon-loaded ruthenium nanoparticle electrocatalyst (Ru@CQDs) for the HER, using carbon quantum dots (CQDs), is reported. Electrochemical tests reveal that, even under extremely alkaline conditions (1 m KOH), the as-formed Ru@CQDs exhibits excellent catalytic behavior with an onset overpotential of 0 mV, a Tafel slope of 47 mV decade^-1 , and good durability. Most importantly, it only requires an overpotential of 10 mV to achieve the current density of 10 mA cm^-2 . Such catalytic characteristics are superior to the current commercial Pt/C and most noble metals, non-noble metals, and nonmetallic catalysts under basic conditions. These findings open a new field for the application of CQDs and add to the growing family of metal@CQDs with high HER performance.

Two-Step Synthesis of Cobalt Iron Alloy Nanoparticles Embedded in Nitrogen-Doped Carbon Nanosheets/Carbon Nanotubes for the Oxygen Evolution Reaction

There is a vital need to explore highly efficient and stable non-precious-metal catalysts for the oxygen evolution reaction (OER) to reduce the overpotential and further improve the energy-conversion efficiency. Herein, we report a unique and cost-effective lyophilization and thermal treatment two-step procedure to synthesize a high-performance hybrid consisting of CoFe alloy nanoparticles embedded in N-doped carbon nanosheets interspersed with carbon nanotubes (CoFe-N-CN/CNTs) hybrid. The lyophilization step during the catalyst preparation leads to a uniform dispersion of carbon-like precursors and avoids the agglomeration of metal particles. In addition, the inserted CNTs and doped N in this hybrid provide a good electrical conductivity, an abundance of chemically active sites, good mass transport capability, and effective gas adsorption/release channels. All these lead to a high specific surface area of 240.67 m²  g^-1 , favorable stability, and remarkable OER activities with an overpotential of only 285 mV at a current density of 10 mA cm^-2 and a Tafel slope of 51.09 mV dec^-1 in 1.0 m KOH electrolyte, which is even superior to commercial IrO₂ catalysts. The CoFe-N-CN/CNTs hybrid thus exhibits great potential as a highly efficient and earth-abundant anode OER electrocatalyst.

Nanoceria-Supported Ruthenium(0) Nanoparticles: Highly Active and Stable Catalysts for Hydrogen Evolution from Water

Ruthenium(0) nanoparticles supported on nanoceria (Ru⁰/CeO₂) were prepared by reduction of Ru³⁺ ions on the surface of ceria using aqueous solution of NaBH₄. The Ru⁰/CeO₂ samples were characterized by advanced analytical tools and employed as electrocatalysts on the glassy carbon electrode (GCE) in hydrogen evolution from water. The GCE, modified by Ru⁰/CeO₂ (1.86 wt % Ru), provides an incredible electrocatalytic activity with a high exchange current density of 0.67 mA·cm^-2, low overpotential of 47 mV at j = 10 mA·cm^-2, and small Tafel slope of 41 mV·dec^-1. Moreover, this modified GCE provides an unprecedented long-term stability without changing the onset potential (33 mV) even after 10 000 scans in acidic water splitting at room temperature. The hydrogen gas, evolved during the water splitting using the Ru⁰/CeO₂ (1.86 wt % Ru) electrocatalyst, was also collected. The amount of the evolved H₂ gas matches well with the calculated value, which indicates the achievement of nearly 100% Faradaic efficiency.

An overview on Pd-based electrocatalysts for the hydrogen evolution reaction

The electrochemical hydrogen evolution reaction (HER) is a well-studied reaction which involves the reduction of protons for hydrogen production. Pd-based compounds are expected to have activity on par with or better than the expensive state-of-the-art Pt and can be considered as the future materials for the HER.

Unique Cu@CuPt Core-Shell Concave Octahedron with Enhanced Methanol Oxidation Activity

Although tremendous efforts have been devoted to the exploration of cost-effective, active, and stable electrochemical catalysts, only few significant breakthroughs have been achieved up to now. Therefore, exploring new catalysts and improving catalyst activity and stability are still major tasks at present. Controllable synthesis of Pt-based alloy nanocrystals with a uniform high-index surface and unique architecture has been regarded as an effective strategy to optimize their catalytic efficiency toward electrochemical reactions. Accordingly, here we present a one-pot facile solvothermal process to synthesize novel unique Cu@CuPt core-shell concave octahedron nanocrystals that exhibit both outstanding activity and long durability. By regulating temperatures during the synthesis process, we were able to control the reduction rate of Cu and Pt ions, which could subsequently lead to the sequential stacking of Cu and Pt atoms. Owing to the concave structure, the as-prepared core-shell nanoparticles hold a high-index surface of {312} and {413}. Such surfaces can provide a high density of atomic steps and terraces, which is suggested to be favorable for electrochemical catalysts. Specifically, the Cu@CuPt core-shell concave octahedron presents 8.6/13.1 times enhanced specific/mass activities toward the methanol oxidation reaction in comparison to those of a commercial Pt/C catalyst, respectively. Meanwhile, the as-prepared catalyst exhibits superior durability and antiaggregation properties under harsh electrochemical conditions. The facile method used here proposes a novel idea to the fabrication of nanocrystals with desired compositional distribution, and the as-prepared product offers exciting opportunities to be applied in direct methanol fuel cells.

Core–shell and alloy integrating PdAu bimetallic nanoplates on reduced graphene oxide for efficient and stable hydrogen evolution catalysts

PdAu nanoplates with different core–shell structures on rGO were generated by manipulating the competition between galvanic replacement and chemical reduction with the alloy and core–shell integrating nanoplates exhibiting superior HER properties.

Decoration of Pd and Pt nanoparticles on a carbon nitride (C3N4) surface for nitro-compounds reduction and hydrogen evolution reaction

Herein, we propose the synthesis of Pd and Pt monometallic nanoparticles on a carbon nitride (C₃N₄) surface for the reduction of nitro compounds as well as for electrocatalysis.