Heterointerface engineering of Ru/RuS2 on N/S-doped hollow mesoporous carbon for promoting alkaline hydrogen evolution

Alkaline hydrogen evolution reaction (HER) suffers from a sluggish kinetic, which requires the elaborate catalytic interface and micro-nanoscale architecture engineering of the electrocatalysts to accelerate the water dissociation and hydrogen evolution. Herein, the heterointerface engineering was proposed for promoting the alkaline HER by constructing the highly exposed Ru/RuS₂ heterostructures homogeneously distributed on hollow N/S-doped carbon microspheres (Ru/RuS₂@h-NSC). Benefited from the synergistic effect of heterointerfacial Ru/RuS₂, the high accessibility of the active sites on both inner and outer surface of mesoporous shells and the efficient mass transport, Ru/RuS₂@h-NSC affords a remarkable catalytic performance with an overpotential of 26 mV@10 mA/cm² for alkaline HER, outperforming most of the state-of-the-art catalysts. Further applying Ru/RuS₂@h-NSC and its oxidized derivate for the overall alkaline water splitting, the required cell voltage is much lower than that of the commercial Pt/C||RuO₂ pair to achieve the same current density. Our study may allow us to guide the design of micro-nanoreactors with optimal catalytic interfaces for promising electrocatalytic applications.     

Benchmarking Three Ruthenium Phosphide Phases for Electrocatalysis of the Hydrogen Evolution Reaction: Experimental and Theoretical Insights

The outstanding electrocatalytic activity of ruthenium (Ru) phosphides toward the hydrogen evolution reaction (HER) has received wide attention. However, the effect of the Ru phosphide phase on the HER performance remains unclear. Herein, a two-step method was developed to synthesize nanoparticles of three types of Ru phosphides, namely, Ru₂P, RuP, and RuP₂, with similar morphology, dimensions, loading density, and electrochemical surface area on graphene nanosheets by simply controlling the dosage of phytic acid as P source. Electrochemical tests revealed that Ru₂P/graphene shows the highest intrinsic HER activity, followed by RuP/graphene and RuP₂/graphene. Ru₂P/graphene affords a current density of 10 mA cm⁻² at an overpotential of 18 mV in acid media. Theoretical calculations further showed that P-deficient Ru₂P has a lower free energy of hydrogen adsorption on the surface than other two, P-rich Ru phosphides (RuP, RuP₂), which confirms the excellent intrinsic HER activity of Ru₂P and is consistent with experiment results. The work reveals for the first time a clear trend of HER activity among three Ru phosphide phases.     

Hollow Nanotube Ru/Cu2+1O Supported on Copper Foam as a Bifunctional Catalyst for Overall Water Splitting

Hydrogen energy is considered as one of the ideal clean energies for solving the energy shortage and environmental issues, and developing highly efficient electrocatalysts for overall water splitting to produce hydrogen is still a huge challenge. Herein, for the first time, Ru-doped Cu₂₊₁O vertically arranged nanotube arrays in situ grown on Cu foam (Ru/Cu₂₊₁O NT/CuF) are reported and further investigated for their catalytic properties for overall water splitting. The Ru/Cu₂₊₁O NT/CuF presents ultrahigh catalytic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline conditions, and it exhibits a small overpotential of 32 mV at 10 mA cm⁻² in the HER, and only needs 210 mV overpotential to achieve a current density of 10 mA cm⁻² in the OER. Importantly, the alkaline electrolyzer using Ru/Cu₂₊₁O NT/CuF as a bifunctional electrocatalyst only needs 1.53 V voltage to deliver a current density of 10 mA cm⁻², which is much lower than the benchmark of IrO₂(+)/Pt(−) counterpart (1.64 V at 10 mA cm⁻²). The excellent performance of the Ru/Cu₂₊₁O NT/CuF catalyst is attributed to its high conductive substrate and special Ru-doped nanotube structure, which provides a high electrochemical active surface area and 3D gas diffusion channel.     

Hierarchical Architectures Based on Ru Nanoparticles/Oxygen-Rich-Carbon Nanotubes for Efficient Hydrogen Evolution

Highly active and durable electrocatalysts are essential for producing hydrogen fuel through the hydrogen evolution reaction (HER). Here, a uniform deposition of Ru nanoparticles strongly interacting with oxygen-rich carbon nanotube architectures (Ru-OCNT) through ozonation and hydrothermal approaches has been designed. The hierarchical structure of Ru-OCNT is made by self-assembly of oxygen functionalities of OCNT. Ru nanoparticles interact strongly with OCNT at the Ru/OCNT interface to give excellent catalytic activity and stability of the Ru-OCNT, as further confirmed by density functional theory. Owing to the hierarchical structure and adjusted surface chemistry, Ru-OCNT has an overpotential of 34 mV at 10 mA cm⁻² with a Tafel slope of 27.8 mV dec⁻¹ in 1 M KOH, and an overpotential of 55 mV with Tafel slope of 33 mV dec⁻¹ in 0.5 M H₂SO₄. The smaller Tafel slope of Ru-OCNT than Ru-CNT and commercial Pt/C in both alkaline and acidic electrolytes indicates high catalytic activity and fast charge transfer kinetics. The as-proposed chemistry provides the rational design of hierarchically structured CNT/nanoparticle electrocatalysts for HER to produce hydrogen fuel.     

Interfacial Electrochemical Behavior of RuS2 Single Crystal Electrodes in Sulfuric Acid Medium

The electrochemical behavior of RuS₂ has been studied using cyclic voltammetry and Energy Dispersive X-ray Spectroscopy (EDX) techniques. Cyclic voltammograms reveal one major anodic peak and two major cathodic peaks on the reverse sweep; these peaks are attributed to the electroadsorption/desorption of OH^? groups on the electrode surface. It is proposed that the electroadsorption of the OH^? group on RuS₂ is due to the presence of Ru 4d electrons in the uppermost part of the valence band. Thus, OH^? is oxidized by holes on Ru 4d states in the first step. These groups are transferred to S₂^2?sites in the second step. EDX surface analysis reveals preferential release of S₂^2? from the pyrite lattice. A mechanism for the anodic dissolution of RuS₂ is proposed, according to which elemental sulfur is not a direct product, but rather the end product which forms from thiosulfate.     

Enhanced catalytic activity of Ru through N modification toward alkaline hydrogen electrocatalysis

Exploring highly efficient electrocatalysts and understanding the reaction mechanisms for hydrogen electrocatalysis,including hydrogen oxidation reaction （HOR） and hydrogen evolution reaction （HER） in alkaline media are conducive to the conversion of hydrogen energy.Herein,we reported a new strategy to boost the HER/HOR performances of ruthenium （Ru） nanoparticles through nitrogen （N） modification.The obtained N-Ru/C exhibit remarkable catalytic performance,with normalized HOR exchange current d...     

Ru-Doping Enhanced Electrocatalysis of Metal–Organic Framework Nanosheets toward Overall Water Splitting

An Ru-doping strategy is reported to substantially improve both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic activity of Ni/Fe-based metal–organic framework (MOF) for overall water splitting. As-synthesized Ru-doped Ni/Fe MIL-53 MOF nanosheets grown on nickel foam (MIL-53(Ru-NiFe)@NF) afford HER and OER current density of 50 mA cm⁻² at an overpotential of 62 and 210 mV, respectively, in alkaline solution with a nominal Ru loading of ≈110 μg cm⁻². When using as both anodic and cathodic (pre-)catalyst, MIL-53(Ru-NiFe)@NF enables overall water splitting at a current density of 50 mA cm⁻² for a cell voltage of 1.6 V without iR compensation, which is much superior to state-of-the-art RuO₂-Pt/C-based electrolyzer. It is discovered that the Ru-doping considerably modulates the growth of MOF to form thin nanosheets, and enhances the intrinsic HER electrocatalytic activity by accelerating the sluggish Volmer step and improving the intermediate oxygen adsorption for increased OER catalytic activity.     

A General Route to Prepare Low‐Ruthenium‐Content Bimetallic Electrocatalysts for pH‐Universal Hydrogen Evolution Reaction by Using Carbon Quantum Dots

A challenging but pressing task to design and synthesize novel, efficient, and robust pH‐universal hydrogen evolution reaction (HER) electrocatalysts for scalable and sustainable hydrogen production through electrochemical water splitting. Herein, we report a facile method to prepare an efficient and robust Ru‐M (M=Ni, Mn, Cu) bimetal nanoparticle and carbon quantum dot hybrid (RuM/CQDs) for pH‐universal HER. The RuNi/CQDs catalysts exhibit outstanding HER performance at all pH levels. The unexpected low overpotentials of 13, 58, and 18 mV shown by RuNi/CQDs allow a current density of 10 mA cm^?2 in 1 m KOH, 0.5 m H₂SO₄, and 1 m PBS, respectively, for Ru loading at 5.93 μgRu cm^?2. This performance is among the best catalytic activities reported for any platinum‐free electrocatalyst. Theoretical studies reveal that Ni doping results in a moderate weakening of the hydrogen bonding energy of nearby surface Ru atoms, which plays a critical role in improving the HER activity.     

A General Route to Prepare Low-Ruthenium-Content Bimetallic Electrocatalysts for pH-Universal Hydrogen Evolution Reaction by Using Carbon Quantum Dots

A challenging but pressing task to design and synthesize novel, efficient, and robust pH-universal hydrogen evolution reaction (HER) electrocatalysts for scalable and sustainable hydrogen production through electrochemical water splitting. Herein, we report a facile method to prepare an efficient and robust Ru-M (M=Ni, Mn, Cu) bimetal nanoparticle and carbon quantum dot hybrid (RuM/CQDs) for pH-universal HER. The RuNi/CQDs catalysts exhibit outstanding HER performance at all pH levels. The unexpected low overpotentials of 13, 58, and 18 mV shown by RuNi/CQDs allow a current density of 10 mA cm⁻² in 1 m KOH, 0.5 m H₂SO₄, and 1 m PBS, respectively, for Ru loading at 5.93 μgRu cm⁻². This performance is among the best catalytic activities reported for any platinum-free electrocatalyst. Theoretical studies reveal that Ni doping results in a moderate weakening of the hydrogen bonding energy of nearby surface Ru atoms, which plays a critical role in improving the HER activity.     

Multifunctional Active‐Center‐Transferable Platinum/Lithium Cobalt Oxide Heterostructured Electrocatalysts towards Superior Water Splitting

Designing cost‐effective and efficient electrocatalysts plays a pivotal role in advancing the development of electrochemical water splitting for hydrogen generation. Herein, multifunctional active‐center‐transferable heterostructured electrocatalysts, platinum/lithium cobalt oxide (Pt/LiCoO₂) composites with Pt nanoparticles (Pt NPs) anchored on LiCoO₂ nanosheets, are designed towards highly efficient water splitting. In this electrocatalyst system, the active center can be alternatively switched between Pt species and LiCoO₂ for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Specifically, Pt species are the active centers and LiCoO₂ acts as the co‐catalyst for HER, whereas the active center transfers to LiCoO₂ and Pt turns into the co‐catalyst for OER. The unique architecture of Pt/LiCoO₂ heterostructure provides abundant interfaces with favorable electronic structure and coordination environment towards optimal adsorption behavior of reaction intermediates. The 30 % Pt/LiCoO₂ heterostructured electrocatalyst delivers low overpotentials of 61 and 285 mV to achieve 10 mA cm^?2 for HER and OER in alkaline medium, respectively.     

A Double Atomic-Tuned RuBi SAA/Bi@OG Nanostructure with Optimum Charge Redistribution for Efficient Hydrogen Evolution

Charge redistribution on surface of Ru nanoparticle can significantly affect electrocatalytic HER activity. Herein, a double atomic-tuned RuBi SAA/Bi@OG nanostructure that features RuBi single-atom alloy nanoparticle supported by Bi−O single-site-doped graphene was successfully developed by one-step pyrolysis method. The alloyed Bi single atom and adjacent Bi−O single site in RuBi SAA/Bi@OG can synergistically manipulate electron transfer on Ru surface leading to optimum charge redistribution. Thus, the resulting RuBi SAA/Bi@OG exhibits superior alkaline HER activity. Its mass activity is up to 65000 mA mg⁻¹ at an overpotential of 150 mV, which is 72.2 times as much as that of commercial Pt/C. DFT calculations reveal that the RuBi SAA/Bi@OG possesses the optimum charge redistribution, which is most beneficial to strengthen adsorption of water and weaken hydrogen-adsorption free energy in HER process. This double atomic-tuned strategy on surface charge redistribution of Ru nanoparticle opens a new way to develop highly efficient electrocatalysts.     

Phosphate-induced interfacial electronic engineering in VPO4-Ni2P heterostructure for improved electrochemical water oxidation

Anodic oxygen evolution reaction（OER） is the key bottleneck for water electrolysis technique owing to its sluggish reaction kinetics. Interfacial engineering on the rationally designed heterostructure can regulate the electronic states efficiently for intrinsic activity improvement. Here, we report a co-phosphorization approach to construct a VPO₄-Ni₂P heterostructure on nickel foam with strongly chemical binding,wherein phosphate acts as electronic modifier for Ni₂     

Highly dispersed Ru/Co catalyst with enhanced activity for catalyzing NaBH4 hydrolysis in alkaline solutions

Ru and Co are highly dispersed on the surface of TiO₂ nanoparticles with an easy coprecipitation method to fabricate a novel Ru-based catalyst (Ru/Co-TiO₂). The fabricated Ru/Co-TiO₂ catalyst exhibits superior catalytic performance for promoting NaBH₄ hydrolysis in alkaline medium, showing an impressive hydrogen generation rate per gram Ru as high as 172 L min⁻¹ g_Ru^-1, which is better than most of recently reported Ru-based catalysts. In addition, the fabricated Ru/Co-TiO₂ catalyst also shows excellent durability in cycle use, with only 2.9% activity loss after being used for 5 cycles. These advantages make the developed Ru/Co-TiO₂ catalyst a potential choice for promoting hydrogen generation from NaBH₄ hydrolysis.     

Heterostructured Inter‐Doped Ruthenium–Cobalt Oxide Hollow Nanosheet Arrays for Highly Efficient Overall Water Splitting

The development of transition‐metal‐oxides (TMOs)‐based bifunctional catalysts toward efficient overall water splitting through delicate control of composition and structure is a challenging task. Herein, the rational design and controllable fabrication of unique heterostructured inter‐doped ruthenium–cobalt oxide [(Ru–Co)O_x] hollow nanosheet arrays on carbon cloth is reported. Benefiting from the desirable compositional and structural advantages of more exposed active sites, optimized electronic structure, and interfacial synergy effect, the (Ru–Co)O_x nanoarrays exhibited outstanding performance as a bifunctional catalyst. Particularly, the catalyst showed a remarkable hydrogen evolution reaction (HER) activity with an overpotential of 44.1 mV at 10 mA cm^?2 and a small Tafel slope of 23.5 mV dec^?1, as well as an excellent oxygen evolution reaction (OER) activity with an overpotential of 171.2 mV at 10 mA cm^?2. As a result, a very low cell voltage of 1.488 V was needed at 10 mA cm^?2 for alkaline overall water splitting.     

Heterostructured Inter-Doped Ruthenium–Cobalt Oxide Hollow Nanosheet Arrays for Highly Efficient Overall Water Splitting

The development of transition-metal-oxides (TMOs)-based bifunctional catalysts toward efficient overall water splitting through delicate control of composition and structure is a challenging task. Herein, the rational design and controllable fabrication of unique heterostructured inter-doped ruthenium–cobalt oxide [(Ru–Co)O_x] hollow nanosheet arrays on carbon cloth is reported. Benefiting from the desirable compositional and structural advantages of more exposed active sites, optimized electronic structure, and interfacial synergy effect, the (Ru–Co)O_x nanoarrays exhibited outstanding performance as a bifunctional catalyst. Particularly, the catalyst showed a remarkable hydrogen evolution reaction (HER) activity with an overpotential of 44.1 mV at 10 mA cm⁻² and a small Tafel slope of 23.5 mV dec⁻¹, as well as an excellent oxygen evolution reaction (OER) activity with an overpotential of 171.2 mV at 10 mA cm⁻². As a result, a very low cell voltage of 1.488 V was needed at 10 mA cm⁻² for alkaline overall water splitting.     

PtM/MxBy (M=Ni,Co, Fe) Heterostructured Nanobundles as Advanced Electrocatalyst for Hydrogen Evolution Reaction

Optimizing the electronic and synergistic effect of hybrid electrocatalysts based on Pt and Pt-based nanocatalysts is of tremendous importance towards a superior hydrogen evolution performance under both acidic and alkaline conditions. However, developing an ideal Pt-based hydrogen evolution reaction (HER) electrocatalyst with moderated electronic structure as well as strong synergistic effect is still a challenge. Herein, we fabricated boron (B)-doped PtNi nanobundles by a two-step method using NaBH₄ as the boron source to obtain PtNi/Ni₄B₃ heterostructures with well-defined nanointerfaces between PtNi and Ni₄B₃, achieving an enhanced catalytic HER performance. Especially, the PtNi/Ni₄B₃ nanobundles (PtNi/Ni₄B₃ NBs) can deliver a current density of 10 mA cm⁻² at the overpotential of 14.6 and 26.5 mV under alkaline and acidic media, respectively, as well as outstanding electrochemical stability over 40 h at the current density of 10 mA cm⁻². Remarkably, this approach is also universal for the syntheses of PtCo/Co₃B and PtFe/Fe₄₉B with outstanding electrocatalytic HER performance.     

Self-Assembled Two-Dimensional NiO/CeO2 Heterostructure Rich in Oxygen Vacancies as Efficient Bifunctional Electrocatalyst for Alkaline Hydrogen Evolution and Oxygen Evolution

The development of high-efficiency bifunctional electrocatalysts toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline surroundings is essential and challenging for the large-scale generation of clean hydrogen. Herein, a novel self-assembled two-dimensional (2 D) NiO/CeO₂ heterostructure (HS) consisting of NiO and CeO₂ nanocrystals is prepared through a facile two-step approach, and utilized as an enhanced bifunctional electrocatalyst for the HER and OER under alkaline conditions. It is concluded that this 2 D NiO/CeO₂ HS, rich in oxygen vacancies, demonstrates attractive electrocatalytic properties for both the HER and OER in 1 m KOH, including low onset overpotential (η₁), η₁₀ and Tafel slope, excellent durability, as well as large active surface area. Therefore, the self-assembled 2 D NiO/CeO₂ HS is believed to be an efficient bifunctional electrocatalyst toward the HER and OER.     

Constructing RuCoOx/NC Nanosheets with Low Crystallinity within ZIF-9 as Bifunctional Catalysts for Highly Efficient Overall Water Splitting

Electrocatalysts play a pivotal role in accelerating the sluggish electrochemical water splitting reaction. Herein, a Ru−Co oxides and carbon nitrides hybrid (RuCoO_x/NC) electrocatalyst was constructed by employing ZIF-9 to disperse Ru precursor and deliberately regulating the calcination temperature. The moderate calcination temperature results in the RuCoO_x nanocomposites with small particle size and low crystallinity as well as the co-existence of multi-valence metal compounds, thus boosting the amount and species of active sites. Moreover, the strong interactions between Co and Ru species induce the electron transfer from Co to Ru, thus enhancing the adsorption of anion intermediates on the electron-deficient Co species and the proton capturing capacity of electron-sufficient Ru species. As a result, the optimized RuCoO_x/NC-350 catalyst behaved good electrocatalytic activities with 73 and 210 mV overpotential to achieve 10 mA cm⁻² for HER and OER, respectively. Remarkably, it showed good durability by holding at 100 mA cm⁻² for 100 h in HER and 50 mA cm⁻² for 24 h in OER with small activity decline. This study may shed new light on the rational construction of highly efficient Ru-based catalysts for electrochemical water splitting.     

Enhanced Metal-Support Interactions Boost the Electrocatalytic Water Splitting of Supported Ruthenium Nanoparticles on a Ni3N/NiO Heterojunction at Industrial Current Density

Developing highly efficient and stable hydrogen production catalysts for electrochemical water splitting (EWS) at industrial current densities remains a great challenge. Herein, we proposed a heterostructure-induced-strategy to optimize the metal-support interaction (MSI) and the EWS activity of Ru-Ni₃N/NiO. Density functional theory (DFT) calculations firstly predicted that the Ni₃N/NiO-heterostructures can improve the structural stability, electronic distributions, and orbital coupling of Ru-Ni₃N/NiO compared to Ru-Ni₃N and Ru-NiO, which accordingly decreases energy barriers and increases the electroactivity for EWS. As a proof-of-concept, the Ru-Ni₃N/NiO catalyst with a 2D Ni₃N/NiO-heterostructures nanosheet array, uniformly dispersed Ru nanoparticles, and strong MSI, was successfully constructed in the experiment, which exhibited excellent HER and OER activity with overpotentials of 190 mV and 385 mV at 1000 mA cm⁻², respectively. Furthermore, the Ru-Ni₃N/NiO-based EWS device can realize an industrial current density (1000 mA cm⁻²) at 1.74 V and 1.80 V under alkaline pure water and seawater conditions, respectively. Additionally, it also achieves a high durability of 1000 h (@ 500 mA cm⁻²) in alkaline pure water.     

Optimizing the electronic structure of Fe-doped Co3O4 supported Ru catalyst via metal-support interaction boosting oxygen evolution reaction and hydrogen evolution reaction

Metal-support interaction(MSI) is an efficient way in heterogeneous catalysis and electrocatalysis to modulate the electronic structure of metal for enhanced catalytic activity. However, there are still great challenges in promoting the hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) simultaneously by this way. Herein, Fe-doped Co₃O₄ supported Ru(Ru/FeCo) catalysts are synthesized by MSI strategies to further improve the electrocatalytic activity and sta...