Lattice and Surface Engineering of Ruthenium Nanostructures for Enhanced Hydrogen Oxidation Catalysis

Ru has recently been considered as a promising alternative of Pt toward hydrogen oxidation reaction (HOR) due to its lower price and similar hydrogen binding energy (HBE) in comparison to Pt. Nevertheless, the catalytic performance of Ru toward HOR is far from the satisfaction of practical application. Herein, it is demonstrated that the modification of Ru multi-layered nanosheet (MLNS) with Ni can significantly promote the HOR performance. In particular, the HOR performance is strongly related to the Ni location on the surface or in the lattice of Ru MLNS. Experimental and theoretical investigations suggest that Ni in the lattice of Ru MLNS (lattice engineering) optimizes the HBE, while Ni species on the surface (surface engineering) decrease the free energy of water formation, as a result of the significantly enhanced HOR performance. The optimal catalyst, where Ni is located both on the surface and in the lattice, displays superior alkaline HOR performance to commercial Pt/C and Ru/C. The present study not only systematically reveals the significance of Ni modification on Ru toward HOR, but also promotes the fundamental researches on catalyst design for fuel cell reactions and beyond.     

Revealing The Role of Electronic Asymmetricity on Supported Ru Nanoclusters for Alkaline Hydrogen Evolution Reaction

Modulating the electronic asymmetricity of catalysts is an effective method for optimizating the elementary steps of water dissociation and hydrogen adsorption/desorption process for the alkaline hydrogen evolution reaction (HER). Herein, uniform Ru nanoclusters anchored on N doped ultrathin carbon nanosheets (Ru/NC) are synthesized to optimize the asymmetricity electronic properties of supported Ru for efficient HER. It is found that Ru and NC with a large work function difference (ΔΦ) leading to the formation of stronger asymmetrical charge distributions of Ru that electron-deficient high-valence Ru (Ruⁿ⁺) coupling with low-valence Ru (Ru⁰). Experimental and theoretical studies indicate the Ruⁿ⁺ sites lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the hydrogen spillover from the Ruⁿ⁺ to Ru⁰ sites, and Ru⁰ sites can enhance H desorption process, thus synergistically enhancing the hydrogen evolution activity. Notably, the Ru/NC catalyst exhibits a high alkaline HER activity (21.9 mV@10 mA cm⁻², 29.03 mV dec⁻¹). The role of electronic asymmetricity on supported Ru nanoclusters for the alkaline HER are demonstrated, which will provide guidelines for the rational design of high-efficiency alkaline HER catalysts.     

Modification of the Intermediate Binding Energies on Ni/Ni3N Heterostructure for Enhanced Alkaline Hydrogen Oxidation Reaction

Developing highly efficient and stable non-precious metal-based electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is essential for the commercialization of alkaline exchange membrane fuel cells but remains a big challenge. Here, a simple strategy for constructing the Ni/Ni₃N heterostructure electrocatalyst with remarkable catalytic performance toward HOR under alkaline electrolyte is reported. Density functional theory calculations and experimental results reveal that the inter-regulated d-band center of interfacial Ni and Ni₃N derived from electron transfer from Ni to Ni₃N across the interface can lead to the weakened hydrogen binding energy of Ni and strengthened hydroxyl binding energy of Ni₃N, which, together with the decreased formation energy of water species, contributes to the outstanding HOR performance.     

Fullerene Lattice-Confined Ru Nanoparticles and Single Atoms Synergistically Boost Electrocatalytic Hydrogen Evolution Reaction

The design and construction of electrocatalysts with high efficiency, low cost and large current output suitable for industrial hydrogen production is the current development trend for water electrolysis. Herein, a lattice-confined in situ reduction effect of the 3D crystalline fullerene network (CFN) is developed to trap Ru nanoparticle (NP) and single atom (SA) via a solvothermal-pyrolysis process. The optimized product (Ru_NP-Ru_SA@CFN-800) exhibits outstanding electrocatalytic performance for alkaline hydrogen evolution reactions. To deliver a current density of 10 mA cm⁻², the Ru_NP-Ru_SA@CFN-800 merely required an overpotential of 33 mV, along with a robust electrocatalytic durability for 1400 h. Even at large current densities of 500 and 1000 mA cm⁻², the overpotentials are only 154 and 251 mV, respectively. Density function theorey calculation results indicated that the electronic synergetic effect between Ru NP and SA enable to regulate the charge distribution of Ru_NP-Ru_SA@CFN-800 and reduce the Gibbs free energy of intermediate species for water dissociation process, thereby accelerating the hydrogen evolution process. Moreover, the robust CFN matrix render this strategy patulous to other transition metals, e.g., Cu, Ni, and Co. The present study provides a new clue for the construction of novel electrocatalyst in the field of energy storage and conversion.     

Triple Interface Optimization of Ru-based Electrocatalyst with Enhanced Activity and Stability for Hydrogen Evolution Reaction

A challenging task is to promote Ru atom economy and simultaneously alleviate Ru dissolution during the hydrogen evolution reaction (HER) process. Herein, Ru nanograins (≈1.7 nm in size) uniformly grown on 1T-MoS₂ lace-decorated Ti₃C₂T_x MXene sheets (Ru@1T-MoS₂-MXene) are successfully synthesized with three types of interfaces (Ru/MoS₂, Ru/MXene, and MoS₂/MXene). It gives high mass activity of 0.79 mA µg_Ru⁻¹ at an overpotential of 100 mV, which is ≈36 times that of Ru NPs. It also has a much smaller Ru dissolution rate (9 ng h⁻¹), accounting for 22% of the rate for Ru NPs. Electrochemical tests, scanning electrochemical microscopy measurements combined with DFT calculations disclose the role of triple interface optimization in improved activity and stability. First, 2D MoS₂ and MXene can well disperse and stabilize Ru grains, giving larger electrochemical active area. Then, Ru/MoS₂ interfaces weakening H^* adsorption energy and Ru/MXene interfaces enhancing electrical conductivity, can efficiently improve the activity. Next, MoS₂/MXene interfaces can protect MXene sheet edges from oxidation and keep 1T-MoS₂ phase stability during the long-term catalytic process. Meanwhile, Ru@1T-MoS₂-MXene also displays superior activity and stability in neutral and alkaline media. This work provides a multiple-interface optimization route to develop high-efficiency and durable pH-universal Ru-based HER electrocatalysts.     

Multisite Synergism-Induced Electron Regulation of High-Entropy Alloy Metallene for Boosting Alkaline Hydrogen Evolution Reaction

Designing the high-entropy alloys (HEAs) electrocatalysts with controllable nanostructures is of great significance for the development of efficient alkaline hydrogen evolution reaction (HER) electrocatalysts. In this study, an ultrathin HEA-PdPtRhIrCu metallene with abundant lattice distortions and defects is prepared via a facile one-step hydrothermal method. The synthesized HEA-PdPtRhIrCu metallene exhibits superior HER performance in a 1 m KOH solution, where the required overpotential of HEA-PdPtRhIrCu metallene is only 15 mV to reach a current density of −10 mA cm⁻² while possessing a low Tafel slope for 37 mV dec⁻¹. Density functional theory calculations further prove that the synergistic effect of the five elements can optimize the electronic structure to enhance the HER activity of the catalysts. In particular, the strong coupling effect and the strong bonding arising from the interaction between the multi-metal components can facilitate the electron transfer of the surface and high electroactivity. Moreover, the optimized Pt electronic structure in HEA-PdPtRhIrCu metallene promotes the optimal Pt H binding at the Pt site, thus promoting HER performance.     

Bifunctional Co3S4 Nanowires for Robust Sulfion Oxidation and Hydrogen Generation with Low Power Consumption

Sulfion oxidation reaction holds great potential for replacing kinetically sluggish water oxidation to save power consumption and simultaneously purifying environmental sulfion-rich sewage. However, it is still challenged by the insufficient mechanism understanding and questionable stability caused by sulfur passivation. Here, it is demonstrated that bifunctional Co₃S₄ nanowires for assembling hybrid seawater electrolyzer that combines anodic sulfion oxidation and cathodic seawater reduction with an ultra-low power consumption of 1.185 kWh m⁻³ H₂ under 100 mA cm⁻², saving energy consumption over 70% compared to the traditional water splitting system. Unlike water is oxidized into O₂ at high potentials under alkaline water splitting system, experiments combined with in situ characterizations uncover the stepwise oxidation of S²⁻ to short-chain polysulfides and then to value-added product of S₈. Density functional theory calculations prove that Co₃S₄ possesses reduced energy barriers in the rate-determining S₃²⁻ to S₄⁻ oxidation step and S₈ desorption step, promoting conversion of short-chain polysulfides and efficient desorption of S₈. These findings reveal the catalytic mechanism of sulfion oxidation and inspire an economic approach toward the fabrication of bifunctional Co₃S₄ for achieving energy-saving hydrogen production from seawater while rapidly disposing sulfion-rich sewage with boosted activity and stability.     

Structure-Induced Stability in Sinuous Black Silicon for Enhanced Hydrogen Evolution Reaction Performance

Clean energy infrastructures of the future depend on efficient, low-cost, long-lasting systems for the conversion and storage of solar energy. This is currently limited by the durability and economic viability of today's solar energy systems. These limitations arise from a variety of technical challenges; primarily, a need remains for the development of stable solar absorber–catalyst interfaces and improved understanding of their mechanisms. Although thin film oxides formed via atomic layer deposition have been widely employed between the solar absorber–catalyst interfaces to improve the stability of photoelectrochemical devices, few stabilization strategies have focused on improving the intrinsic durability of the semiconductor. Here, a sinuous black silicon photocathode (s-bSi) with intrinsically improved stability owing to the twisted nanostructure is demonstrated. Unlike columnar black silicon with rapidly decaying photocurrent density, s-bSi shows profound stability in strong acid, neutral, and harsh alkaline conditions during a 24-h electrolysis. Furthermore, scanning transmission electron microscopy studies prior to and post electrolysis demonstrate limited silicon oxide growth inside the walls of s-bSi. To the authors’ knowledge, this is the first time structure-induced stability has been reported for enhancing the stability of a photoelectrode/catalyst interface for solar energy conversion.     

Ru Species Supported on MOF‐Derived N‐Doped TiO2/C Hybrids as Efficient Electrocatalytic/Photocatalytic Hydrogen Evolution Reaction Catalysts

The development of efficient catalysts is of great importance for hydrogen evolution reaction (HER) of water splitting via electrocatalytic/photocatalytic processes to remediate the current severe environmental and energy problems. By aid of the stabilization effects of uncoordinated groups and inherent pore‐confinement of amine‐functionalized metal–organic frameworks (NH₂‐MIL‐125), two forms of Ru species including nanoparticles (NPs) and/or single atoms (SAs) can be firmly embedded in NH₂‐MIL‐125 derived N‐doped TiO₂/C support (N‐TC), and thus obtain two kinds of samples named Ru‐NPs/SAs@N‐TC and Ru‐SAs@N‐TC, respectively. In the synthetic process, the initial feeding amount of Ru³⁺ ions not only strongly determines the final size and dispersion states of Ru species but also the morphology and defective structures of N‐TC support. Impressively, Ru‐NPs/SAs@N‐TC exhibit superior catalytic activities to Ru‐SAs@N‐TC for either electrocatalytic or photocatalytic HER. This should be attributed to its larger specific surface area and benefiting from synergistic coupling of Ru NPs and Ru SAs. It is envisioned that the present work can provide a new avenue for development of high‐efficiency and multifunctional hybrid catalysts in sustainable energy conversion.     

In Situ Construction of Ni/Ni0.2Mo0.8N Heterostructure to Enhance the Alkaline Hydrogen Oxidation Reaction by Balancing the Binding of Intermediates

The inferior activity of hydrogen oxidation reaction (HOR) in alkali severely hampers the deployment of Ni catalysts in the promising anion exchange membrane fuel cells (AEMFCs), due to the unbalanced binding energies of hydrogen (HBE) and hydroxyl (OHBE) species. Ni-Mo alloy and nickel nitride have been proven to improve the Ni-based activities of HOR but they still can be further enhanced. Because it sacrifices the HBE for enlarging OHBE. Herein, it is reported that the activity can be further improved by constructing heterostructure between Ni nanoparticles (NPs) and nitride of Ni-Mo alloy (Ni_0.2Mo_0.8N) by an in situ synthetic strategy. The in situ prepared reduced graphene oxide (rGO) supported heterostructure (Ni/Ni_0.2Mo_0.8N/rGO) possesses the state-of-the-art activity (overpotential of 100 mV to achieve 2.9 mA cm⁻²), faster kinetics (kinetics current density of 11.20 mA cm⁻² and exchange current density of 2.74 mA cm⁻²), and ultrahigh durability (maintaining the current densities for over 40 h or 10000 cycles). Detailed characterizations together with density functional theory simulations reveal that the tuned d-band electronic structures optimize and balance the HBE and OHBE, facilitating the HOR process on the as-fabricated heterostructured catalyst.     

重掺杂直拉硅单晶氧化诱生缺陷的无铬腐蚀研究

采用无铬和含铬两种溶液共同腐蚀不同型号、不同掺杂剂和不同晶向的重掺单晶样品,研究如何更好地使用无铬腐蚀液显示重掺杂晶体氧化诱生缺陷.实验表明反应过程中温度控制在25～30℃,腐蚀液中适当增加缓冲溶剂,可以很好地控制表面腐蚀速度.实验还发现,对于<100>重掺样品,使用有搅拌的改良Dash无铬溶液显现的损伤缺陷密度低于有铬择优腐蚀液.而对于<111>重掺样品,未见明显差异.最后,探讨了在使用无铬溶液显示重掺Sb晶体缺陷时,缺陷难显现,而且密度低的原因.     

Realizing the Synergy of Interface Engineering and Chemical Substitution for Ni3N Enables its Bifunctionality Toward Hydrazine Oxidation Assisted Energy-Saving Hydrogen Production

Hydrazine oxidation assisted water electrolysis offers a unique rationale for energy-saving hydrogen production, yet the lack of effective non-noble-metal bifunctional catalysts is still a grand challenge at the current stage. Here, the Mo doped Ni₃N and Ni heterostructure porous nanosheets grow on Ni foam (denoted as Mo Ni₃N/Ni/NF) are successfully constructed, featuring simultaneous interface engineering and chemical substitution, which endow the outstanding bifunctional electrocatalytic performances toward both hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER), demanding a working potential of −0.3 mV to reach 10 mA cm⁻² for HzOR and −45 mV for that of HER. Impressively, the overall hydrazine splitting (OHzS) system requires an ultralow cell voltage of 55 mV to deliver 10 mA cm⁻² with remarkable long-term durability. Moreover, as a proof-of-concept, economical H₂ production systems utilizing OHzS unit powered by a waste AAA battery, a commercial solar cell, and a homemade direct hydrazine fuel cell (DHzFC) are investigated to inspire future practical applications. The density functional theory calculations demonstrate that the synergy of Mo substitution and abundant Ni₃N/Ni interface owns a more thermoneutral value for H* absorption ability toward HER and optimized dehydrogenation process for HzOR.     

Construction of Ru,O Co-Doping MoS2 for Hydrogen Evolution Reaction Electrocatalyst and Surface-Enhanced Raman Scattering Substrate: High-Performance,Recyclable, and Durability Improvement

Molybdenum disulfide (MoS₂) is a promising non-precious material for hydrogen evolution reaction (HER) electrocatalysts and surface-enhanced Raman scattering (SERS) substrates. However, its inert basal plane, poor active sites, and limited stability hamper their commercial prospects. Herein, Ru, O co-doped MoS₂ (MSOR_x) for accelerating the charge transfer and building more active sites using one-step hydrothermal method is designed to address these obstacles. The outstanding HER performances of the MSOR₁ with low overpotentials at 10 mA cm⁻² in both acidic (197 mV) and alkaline solution (43 mV), which even rivals that of commercial Pt/C. Meanwhile, this MSOR₁ is also used as SERS substrate that has excellent sensitivity with the enhancement factor of 1.7 × 10⁶. Additionally, label-free detection of bilirubin using MSOR₁ with a detection limit of 10⁻¹⁰ m has been demonstrated, also better than that of most previously reported semiconductors. Superior HER and SERS activity, universality in wide PH range and long-term stability are achieved based on the introduction of Ru and O. This study provides guidance for the synthesis of highly active catalysts and SERS substrate, and holds considerable promise for low-cost HER over the whole pH and clinical translation in accurate diagnosis of jaundice.     

Synthesis of CeOx‐Decorated Pd/C Catalysts by Controlled Surface Reactions for Hydrogen Oxidation in Anion Exchange Membrane Fuel Cells

Due to the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline electrolytes, the development of more efficient HOR catalysts is essential for the next generation of anion‐exchange membrane fuel cells (AEMFCs). In this work, CeO_x is selectively deposited onto carbon‐supported Pd nanoparticles by controlled surface reactions, aiming to enhance the homogenous distribution of CeO_x and its preferential attachment to Pd nanoparticles, to achieve highly active CeO_x‐Pd/C catalysts. The catalysts are characterized by inductively coupled plasma–atomic emission spectroscopy, X‐ray diffraction, high‐resolution transmission electron microscopy, scanning transmission electron microscopy (STEM), electron energy loss spectroscopy, and X‐ray photoelectron spectroscopy to confirm the bulk composition, phases present, morphology, elemental mapping, local oxidation, and surface chemical states, respectively. The intimate contact between Pd and CeO_x is shown through high‐resolution STEM maps. The oxophilic nature of CeO_x and its effect on Pd are probed by CO stripping. The interfacial contact area between CeO_x and Pd nanoparticles is calculated for the first time and correlated to the electrochemical performance of the CeO_x‐Pd/C catalysts. Highest recorded HOR specific exchange current (51.5 mA mg^?1_Pd) and H₂–O₂ AEMFC performance (peak power density of 1,169 mW cm^?2 mg_Pd^?1) are obtained with a CeO_x‐Pd/C catalyst with Ce_0.38/Pd bulk atomic ratio.     

Single Platinum Atoms Immobilized on Monolayer Tungsten Trioxide Nanosheets as an Efficient Electrocatalyst for Hydrogen Evolution Reaction

Monolayer WO₃·H₂O (ML-WO₃·H₂O) nanosheets are synthesized via a space-confined strategy, and then a single-atom catalyst (SAC) is constructed by individually immobilizing Pt single atoms (Pt-SA) on monolayer WO₃ (ML-WO₃). The Pt-SA/ML-WO₃ retains the monolayer structure of ML-WO₃·H₂O, with a quite high monolayer ratio up to ≈ 93%, and possesses rich defects (O and W vacancies). It exhibits excellent electrocatalytic performance, with a small overpotential (η) of − 22 mV to drive − 10 mA cm⁻² current, a low Tafel slope of ≈ 27 mV dec⁻¹, an ultrahigh turnover frequency of ≈ 87 H₂ s⁻¹ site⁻¹ at η  =   − 50 mV, and long-term stability. Of particular note, it exhibits an ultrahigh mass activity of ≈ 87 A mg_Pt⁻¹ at η  =   − 50 mV, which is ≈ 160 times greater than that of the state-of-the-art commercial catalyst, 20 wt% Pt/C ( ≈ 0.54 A mg_Pt⁻¹). Experimental and DFT analyses reveal that its excellent performance arises from the strong synergetic effect between the single Pt atoms and the support. This work provides an effective route for large-scale fabrication of ML-WO₃ nanosheets, demonstrates ML-WO₃ is an excellent support for SACs, and also reveals the great potential of SACs in reducing the amount of noble metals used in catalysts.     

Ultrahigh Mass Activity for the Hydrogen Evolution Reaction by Anchoring Platinum Single Atoms on Active {100} Facets of TiC via Cation Defect Engineering

Improving the platinum (Pt) mass activity for low-cost electrochemical hydrogen evolution is an important and arduous task. Here, a selective etching-reducing fluidized bed reactor technique is reported to create Ti vacancies and firmly anchor single Pt atoms on the active {100} facets of titanium carbide (TiC) to increase the Pt utilization efficiency and improve catalytic activity significantly by a synergistic effect between Ti vacancies and Pt atoms. The generated Ti vacancies are negatively charged and stabilize Pt atoms by forming covalent Pt C bonds, showing excellent long-term durability. Pt single atoms (ultralow load of 1.2 µg cm⁻²) on the defective TiC {100} show remarkable activity (24.9 mV at 10 mA cm⁻²) and a mass activity (49.69 A mg⁻¹) ≈190 times that of the state-of-the-art Pt C catalyst and nearly double the previously reported best values. The developed cation defect engineering exhibits excellent potential for fabricating next-generation advanced single-atom catalysts for large-scale hydrogen evolution at a low cost.