High-performance Hydrogen Evolution Reaction Research Articles

Re nanoflower-decorated carbon cloth for pH-universal hydrogen evolution reaction: Unveiling the intrinsic electrocatalytic activity of metallic Re

The hydrogen evolution reaction (HER) is one of the primary routes for clean hydrogen energy production to replace fossil fuels. However, the lack of cost-effective electrocatalysts hinders its practical implementation. Re, which is considerably less expensive than Pt, has recently emerged as an electrocatalyst owing to its high HER activity over a wide pH range. However, HER processes of Re have been studied primarily through spectroscopy, with little theoretical interpretation to explain the intrinsic HER activity of Re. Additionally, it is necessary to develop antioxidative Re electrocatalysts to prevent hydrogen intercalation, and to suppress catalyst aggregation to ensure long-term stability. In this work, a theoretical analysis was first conducted to investigate the free energy of each HER intermediate and demonstrate high performance of Re. Then, a novel free-standing electrocatalyst consisting of Re nanoflowers (NFs) grown in-situ on a carbon cloth (CC) was synthesized (ReNF@CC) via a hydrothermal method followed by thermal annealing. The Re NFs homogeneously grown on the CC surface effectively suppressed self-aggregation to preserve abundant active sites, and the direct coupling of Re NFs enhanced the conductivity and physical/electrochemical stability to prevent their detachment from the CC during operation. A high HER performance was obtained with low overpotentials of 103, 115, and 75 mV at 10 mA cm−2 in 0.5 M H2SO4, 1 M PBS, and 1 M KOH, respectively; additionally, a superior durability with respect to commercial Pt/C was achieved. Overall, this study offers a versatile and universal strategy for highly efficient water electrolysis in different media.

Hollow Nanowire Constructed by NiCo Doped RuO2 Nanoparticles for Robust Hydrogen Evolution at High-Current-Density.

Large-current-density electrocatalytic water splitting is essential for industrial hydrogen production, but it is currently hindered by lacking active and robust hydrogen evolution reaction (HER) catalysts. Herein, a novel electrode of hollow nanowire arrays constructed by NiCo modified RuO2 nanoparticles on Ni foam (NiCo@RuO2 HNAs/NF) for high-performance HER was reported. Such efficient electrode was fabricated by ion exchange with NF-supported Ni modified cobalt carbonate hydroxide nanowire arrays template (Ni@CoCH NAs/NF). The formed NiCo@RuO2 HNAs/NF only needed overpotentials of 148.5 and 236.1 mV to deliver 500 and 1000 mA cm-2 , respectively, along with excellent stability at the high-current-density for 300 h. Such remarkable HER performance was mainly attributed to the hollow structure with high surface area, hydrophilic feature, and NiCo@RuO2 with optimized hydrogen evolution kinetics. After coupling with anodic Ni@CoCH NAs/NF, our electrolyzer outperformed Pt/C-IrO2 and most other Ru-based electrolyzers. This work provides a promising Pt alternative catalyst for profitable H2 production.

High-Entropy Alloy Nanosheets for Fine-Tuning Hydrogen Evolution

The electrolysis of water is promising for hydrogen production. The development of high-performance and low-cost hydrogen evolution reaction (HER) electrocatalysts is particularly important for the wide application of water electrolyzers. Tuning the hydrogen binding energy (HBE) of materials is an effective way to optimize the HER electrocatalysts, particularly for applications in an acidic environment. Here, we report the discovery of a Pt-free combination, PdMoGaInNi, which has the HBE optimum, via computer-facilitated screening. As the exploratory example of the two-dimensional high-entropy alloy (HEA) for HER, the PdMoGaInNi HEA nanosheets were synthesized to realize the predicted Pt-free combination with optimal HBE. The PdMoGaInNi HEA nanosheets exhibit a high HER activity with low overpotentials of 13 mV at 10 mA cm–2, outperforming commercial Pd/C and Pt/C catalysts. Given the high entropy, lattice distortion, and sluggish diffusion effects of HEA, the PdMoGaInNi shows great long-term durability for at least 200 h in a proton exchange membrane water electrolyzer.

Three dimensional Ti3C2Tx and rGO hybrid supported Pt catalyst for the high performance hydrogen evolution reaction

The effective electrocatalysts for hydrogen evolution reaction (HER) in alkaline aqueous is critical point to reduce energy losses for water electrolysis. Here, a highly active and stable electrochemical catalyst of platinum (Pt) nanoparticles loaded on three-dimensional Ti3C2Tx-reduced graphite oxide (rGO) hybrid support (Pt/Ti3C2Tx-rGO3D) has been developed for hydrogen evolution reaction (HER). The large surface of 3 D support provides an adequate site for deposition of Pt nanoparticles, leading to superior HER activity with low overpotential about 41 mV and better stability than Pt/C. This study offers a hybrid support for the development of highly active electrocatalysts for hydrogen evolution reaction.

Co(OH)2 promoting the catalytic activity of CoP/Ni2P heterojunction for hydrogen evolution in both alkaline and acid media

Developing non-precious metal catalysts to replace commercial Pt for hydrogen evolution reaction (HER) is extremely significant for practical application of water splitting. Here, we synthesized a composite CoP/Ni2P@Co(OH)2 catalyst via the sequential phase growth strategy. Owing to the cooperative effect between CoP/Ni2P and Co(OH)2, the CoP/Ni2P@Co(OH)2 catalyst presents excellent HER catalytic performance with 39 mV overpotential in 1 M KOH and 68 mV overpotential in 0.5 M H2SO4 to deliver the current density of 10 mA cm−2. By designing a control experiment, we found that the Co(OH)2 may promote water dissociation effectively in alkaline media and accelerate the generation of M-H∗ in acidic media, while CoP/Ni2P can serve as the active sites for the adsorption and desorption of hydrogen. The synergistic effects of CoP/Ni2P and Co(OH)2 greatly boost its HER catalytic performance in both alkaline and acid media. In short, the new finding of introducing Co(OH)2 into the CoP/Ni2P can accelerate the development of high-performance HER catalysts.

Three-dimensional ordered macroporous design of heterogeneous nickel-iron phosphide as bifunctional electrocatalyst for enhanced overall water splitting

Developing high-performance oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) bifunctional electrocatalysts is essential for overall water splitting. Herein, heterogeneous engineering-induced strategy was demonstrated by the synthesis of bimetallic Ni2P/FeP/Fe2P heterostructure with three-dimensional ordered macroporous structure (3DOM-Ni2P/FexP) as bifunctional catalyst. The heterogeneous interfaces formed by the three distinct phases can adjust the electron distribution and create abundant active sites to improve the catalytic performance. The 3DOM structure provides large specific surface area and good mass transfer for electrocatalytic reaction occurring at the solid-gas-electrolyte multiphase interfaces. Accordingly, the 3DOM-Ni2P/FexP showed remarkable OER and HER electrocatalytic activity in 1 M KOH electrolyte. Moreover, it demonstrates that the 3DOM-Ni2P/FexP turns out oxidation and transformation during the OER process. Computational results reveal the synergy of the converted Fe2O3/NiOOH, promoting the OER reaction energetics. In addition, an alkaline electrolyzer with the 3DOM-Ni2P/FexP as both the cathode and anode achieves excellent overall water splitting performance, with only 1.54 V voltage to obtain the current density of 10 mA cm−2. This present study gives a novel concept of heterogeneous engineering-induced bimetallic phosphide with macroporous structure design towards the high-performing OER and HER bifunctional electrocatalysts evolvement.

Carbon dots modified molybdenum disulfide as a high-efficiency hydrogen evolution electrocatalyst

Molybdenum disulfide (MoS2) is considered a low-cost material that may replace platinum-based electrocatalysts towards hydrogen evolution reaction (HER). However, the catalytic activity of MoS2 is limited by the low conductivity and lack of active sites. Here, a biomass carbon dots-molybdenum disulfide (BCDs-MoS2) composite was synthesized as a HER catalyst by a simple hydrothermal method. The BCDs-MoS2 catalyst displayed excellent electrocatalytic performance for HER with lower onset overpotential (115 mV), smaller Tafel slope (56.57 mV dec−1) as well as high cycling stability, which superior to those of homemade MoS2, commercial MoS2, and most of the reported MoS2-based catalysts. According to the characterization results of morphology, surface properties, and valence states of elements, the outstanding catalytic activity of BCDs-MoS2 is ascribed to its loose structure with a large specific surface area along with abundant edges and defects, and the increase in the amount of S22− and S2− which possess higher activity due to the addition of the BCDs. This study can afford a new strategy to design high performance HER catalysts.

Inverted-design for highly-active hydrogen evolution electrocatalyst of MoS2@Ni3S2 core-shell via unlocking the potential of Mo

Through inverted-design rather than modifying the generally-assumed S active sites in popular MoS2, we unlock the potential of Mo sites and successfully prepared novel MoS2@Ni3S2/NF core-shell nanospheres as a catalyst for the high-performance hydrogen evolution reaction (HER). The ΔGH at the Mo site is optimized via Ni3S2 to achieve excellent HER activity. At low current densities, it has similar activity to the Pt/C. However, its performance is better than Pt/C at high density. Moreover, our catalyst shows a considerable stability at a variety of current densities for 50 h, promising to substitute noble metal catalysts in application of commercial alkaline electrocatalysts.

Electrochemical Preparation of Nanocatalysts and Their Application in Electrocatalysis.

In order to solve the basic problem of high-temperature sintering of molybdenum carbide restricting the efficient construction of molybdenum carbide nanostructures and the full play of hydrogen evolution performance, this article studies the preparation of nano molybdenum carbide/boron nitrogen codoped two-dimensional carbon composite structure catalysts and the electrochemical hydrogen evolution reaction performance. Based on the self-assembly process of gelatin molecules on the surface of a two-dimensional layered boric acid crystal template, a new strategy for constructing a high-performance electrochemical hydrogen evolution reaction catalyst based on molybdenum carbide/boron nitrogen codoped two-dimensional nanocarbon composite structure (η-MoC@ BN-CSs) was established. The experimental results show that the overpotential of hydrogen evolution reaction based on molybdenum carbide/boron nitrogen codoped two-dimensional nanocarbon composite structure catalyst is 159 mV, which is slightly higher than 67 mV of commercial Pt/C catalyst, but lower than the reported literature value in the list. The Tafel slope is 68 mV·dec−1, which is slightly higher than that of the commercial Pt/C catalyst (40 mV·dec−1) and the reference value (58 mV·dec−1), but lower than those of other reported literature values in the list, indicating that the molybdenum carbide/boron nitrogen codoped two-dimensional carbon nanocomposites have excellent catalytic performance under alkaline conditions. Conclusion. This kind of two-dimensional nanocomposite structure shows platinum-like catalytic activity when used as an electrochemical hydrogen evolution catalyst in alkaline electrolyte. It has better reaction kinetics and better stability.

Physical insights into alkaline overall water splitting with NiO microflowers electrodes with ultra-low amount of Pt catalyst

Electrochemical water splitting represents a promising alternative to conventional carbon-based energy sources. The hydrogen evolution reaction (HER) is a key process, still if conducted in alkaline media, its kinetics is slow thus requiring high amount of Pt based catalysts. Extensive research has been focused on reducing Pt utilization by pursuing careful electrode investigation. Here, a low-cost chemical methodology is reported to obtain large amount of microflowers made of interconnected NiO nanowalls (20 nm thick) wisely decorated with ultralow amounts of Pt nanoparticles. These decorated microflowers, dispersed onto graphene paper by drop casting, build a high performance HER electrode exhibiting an overpotential of only 66 mV at current density of 10 mA cm−2 under alkaline conditions. Intrinsic activity of catalyst was evaluated by measuring the Tafel plot (as low as 82 mV/dec) and turnover frequencies (2.07 s−1 for a Pt loading of 11.2 μg cm−2). The effect of Pt decoration has been modelled through energy band bending supported by electrochemical analyses. A full cell for alkaline electrochemical water splitting has been built, composed of Pt decorated NiO microflowers as cathode and bare NiO microflowers as anode, showing a low potential of 1.57 V to afford a current density of 10 mA cm−2 and a good long-term stability. The reported results pave the way towards an extensive utilization of Ni based nanostructures with ultralow Pt content for efficient electrochemical water splitting.

Strategies for Designing High-Performance Hydrogen Evolution Reaction Electrocatalysts at Large Current Densities above 1000 mA cm-2.

The depletion of fossil fuels and rapidly increasing environmental concerns have urgently called for the utilization of clean and sustainable sources for future energy supplies. Hydrogen (H2) is recognized as a prioritized green resource with little environmental impact to replace traditional fossil fuels. Electrochemical water splitting has become an important method for large-scale green production of hydrogen. The hydrogen evolution reaction (HER) is the cathodic half-reaction of water splitting that can be promoted to produce pure H2 in large quantities by active electrocatalysts. However, the unsatisfactory performance of HER electrocatalysts cannot follow the extensive requirements of industrial-scale applications, including working efficiently and stably over long periods of time at high current densities (⩾1000 mA cm-2). In this review, we study the crucial issues when electrocatalysts work at high current densities and summarize several categories of strategies for the design of high-performance HER electrocatalysts. We also discuss the future challenges and opportunities for the development of HER catalysts.

Biohybrid Organic Heterostructure Based on Chlorophyll‐Bacteriochlorophyll Aggregates for Ecofriendly Hydrogen Production

Hydrogen energy is an abundant, clean, sustainable and environmentally friendly renewable energy source. Therefore, the production of hydrogen by photocatalytically splitting water on semiconductors has been considered in recent years as a promising and sustainable strategy for converting solar energy into chemical energy to replace conventional energy sources and to solve the growing problem of environmental pollution and the global energy crisis. However, highly efficient solar-driven photocatalytic hydrogen production remains a huge challenge due to the poor visible light response of available photocatalytic materials and the low efficiency of separation and transfer of photogenerated electron-hole pairs. In the present work, organic heterojunction structures based on bacteriochlorophyll (BChl) and chlorophyll (Chl) molecules were introduced and used for solar-driven photocatalytic hydrogen production from water under visible light. Also, noble metal-free photocatalyst was successfully constructed on Ti3 C2 Tx nanosheets by simple successive deposition of Chl and BChl, which was used for the photocatalytic splitting water to hydrogen evolution reaction (HER). The results show that the optimal BChl@Chl@Ti3 C2 Tx composite has a high HER performance with 114 μmol/h/gcat , which is much higher than the BChl@Ti3 C2 Tx and Chl@Ti3 C2 Tx composites.

Chemical Energy‐Driven Lithiation Preparation of Defect‐Rich Transition Metal Nanostructures for Electrocatalytic Hydrogen Evolution

Transition metal nanostructures are widely regarded as important catalysts to replace the precious metal Pt for hydrogen evolution reaction (HER) in water splitting. However, it is difficult to obtain uniform-sized and ultrafine metal nanograins through general high-temperature reduction and sintering processes. Herein, a novel method of chemical energy-driven lithiation is introduced to synthesize transition metal nanostructures. By taking advantage of the slow crystallization kinetics at room temperature, more surface and boundary defects can be generated and remained, which reduce the atomic coordination number and tune the electronic structure and adsorption free energy of the metals. The obtained Ni nanostructures therein exhibit excellent HER performance. In addition, the bimetal of Co and Ni shows better electrocatalytic kinetics than individual Ni and Co nanostructures, reaching 100mAcm-2 at a low overpotential of 127mV. The high HER performance originates from well-formed synergistic effect between Ni and Co by tuning the electronic structures. Density functional theory simulations confirm that the bimetallic NiCo possesses a low Gibbs free energy of hydrogen adsorption, which are conducive to enhance its intrinsic activity. This work provides a general strategy that enables simultaneous defect engineering and electronic modulation of transition metal catalysts to achieve an enhancement in HER performance.

Microwave synthesis of Sb2Se3/polyacrylonitrile-based carbon fiber mat electrodes for high-performance flexible capacitors and hydrogen evolution reaction

The development of bifunctional electrodes with good capacitive performance and efficient hydrogen evolution reaction activity is one of the potential solutions to combat energy depletion. In this study, flexible polyacrylonitrile-based carbon fiber mat with nitrogen doping and oxygen-containing functional group carbon structure was selected as the flexible substrate, and binder-free flexible Sb2Se3/polyacrylonitrile-based carbon fiber mat composite electrode was successfully prepared within 120 s using microwave synthesis. The electrode not only has a capacitance of 478.0C g−1 and retains 97.4% of the initial capacitance after 50,000 charge–discharge tests but also exhibits good HER activity of low overpotential (152 mV) and Tafel slope (78.4 mV/dec) in alkaline electrolyte. The performance of the assembled flexible asymmetric supercapacitor is almost unaffected by bending up to 180°. The device has an energy density of 21.3 Wh kg−1 at a power density of 800.0 W kg−1, indicating that the electrode has good prospects for portable energy storage applications.

Highly dispersed platinum deposited on nitrogen-doped vertical graphene array for efficient electrochemical hydrogen evolution

The electrochemical hydrogen evolution is a key technology for future renewable energy conversion and storage. Platinum is the most efficient catalyst for hydrogen evolution reaction (HER), but its mass activity should be boosted further. Herein, we deposited platinum on nitrogen-doped vertical graphene through an atomic layer deposition method. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy confirmed that the platinum was highly dispersed on the array substrate. On account of the array structure and high dispersion of platinum, the synthesized catalyst exhibited high HER performance with a low overpotential of 42 mV at 10 mA cm−2 and a low Tafel slope of 52.2 mV dec−1. Significantly, the synthesized catalyst exhibited a high mass activity of 4.45 A mg−1 Pt, which was ∼13 times higher than that of commercial Pt/C.

Boosting Hydrogen Evolution Reaction Activity of Amorphous Molybdenum Sulfide Under High Currents Via Preferential Electron Filling Induced by Tungsten Doping.

The lack of highly efficient, durable, and cost‐effective electrocatalysts for the hydrogen evolution reaction (HER) working at high current densities poses a significant challenge for the large‐scale implementation of hydrogen production from renewable energy. Herein, amorphous molybdenum tungsten sulfide/nitrogen‐doped reduced graphene oxide nanocomposites (a‐MoWSx/N‐RGO) are synthesized by plasma treatment for use as high‐performance HER catalysts. By adjusting the plasma treatment duration and chemical composition, an optimal a‐MoWSx/N‐RGO catalyst is obtained, which exhibits a low overpotential of 348 mV at a current density of 1000 mA cm−2 and almost no decay after 24 h of working at this current density, outperforming commercial platinum/carbon (Pt/C) and previously reported heteroatom‐doped MoS2‐based catalysts. Based on density functional theory (DFT) calculations, it is found that with a reasonable tungsten doping level, the catalytic active site (2S2 − ) shows excellent catalytic performance working at high current densities because extra electrons preferentially fill at 2S2 − . The introduction of tungsten tends to lower the electronic structure energy, resulting in a closer‐to‐zero positive ΔGH∗. Excessive tungsten introduction, however, can lead to structural damage and a worse HER performance under high current densities. The work provides a route towards rationally designing high‐performance catalysts for the HER at industrial‐level currents using earth‐abundant elements.

Self-activatable carbon nanotube@ruthenium-catechol coordination complex for hydrogen evolution reaction

We report a simple metal ion-catechol coordination strategy to coat ruthenium-catechol polymer complex (TAC-Ru) on the surface of carbon nanotubes (CNT) to form a core–shell structure (abbreviated as CNT@TAC-Ru). This is achieved by firstly polymerizing catechol and boronic acid monomers on the surface of CNT to form a boronate ester polymer (BP) shell. Then, Ru3+ is used to etch the BP shell, and cleave the dynamic boronate ester bond, leading to the formation of a CNT@ruthenium-catechol coordination complex based on the coordinative efficiency of the catechol group. The electrocatalytic property of the CNT@TAC-Ru composite can be activated through electrochemical cycling treatment. The as-activated CNT@TAC-Ru exhibits evidently improved hydrogen evolution reaction (HER) performance with an overpotential of 10 mV in 1.0 M KOH at a current density of 10 mA cm−2 , which is better than that of commercial Pt/C (32 mV). And the long-term stability is also desirable. This work provides a pyrolysis-free method to form metal-polymer-carbon composite with high HER performance under the alkaline condition.

Boosting Highly Active Exposed Mo Atoms by Fine-Tuning S-Vacancies of MoS2-Based Materials for Efficient Hydrogen Evolution.

Guided by the theoretical calculation, achieving an efficient hydrogen evolution reaction (HER) by S-vacancy engineering toward MoS2-based materials is quite challenging due to the contradictory relationship between the adsorption free energy of hydrogen atoms (ΔGH) of the exposed Mo atoms (EMAs) and the number of EMAs per unit area (NEMAs). Herein, we demonstrate a novel one-pot incorporating-assisted compositing strategy to realize fine-tuning the concentration of S-vacancies (CS-vacancies) of MoS2-based materials to boost highly active EMAs for efficient HER. In our strategy, S-vacancies are modulated into basal planes of MoS2 via decreasing the formation energy of S-vacancies by oxygen incorporation; moreover, CS-vacancies of the basal planes is precisely regulated by simply controlling the molar amount of the Co precursor based on the electron injection effect. At low or excessively high CS-vacancies, the as-synthesized electrocatalysts lack "highly active EMAs" in quantity or nature. The balance between the intrinsic activity of EMAs and NEMAs is realized for boosting EMAs with high catalytic performance. The optimal electrocatalysts exhibit excellent activity and stability at fine-tuning CS-vacancies to 9.61%. Our results will pave a novel strategy for unlocking the potential of an inert basal plane in MoS2 for high-performance HER.

Ordered macroporous superstructure of bifunctional cobalt phosphide with heteroatomic modification for paired hydrogen production and polyethylene terephthalate plastic recycling

The integration of cathodic hydrogen evolution reaction (HER) with thermodynamically favorable anodic oxidation reactions offers a sustainable alternative for electrochemical valorization. Herein, the atomic Ni modified CoP electrocatalyst featuring an elaborate ordered macroporous superstructure with abundant built-in mesopores has been developed from the ordered macroporous ZIF-67 single crystals, of which the distinctive structural advantages lead to a high HER performance. When the catalyst further underwent an electrochemical reconstruction, an outstanding activity with high Faradaic efficiency up to 96% of formate for ethylene glycol oxidation reaction (EGOR) can be afforded in alkaline electrolyte, as well as in the complex electrolyte of polyethylene terephthalate (PET) plastic hydrolysate. Remarkably, an exotic energy-saving pair-electrolysis system coupling HER and EGOR was explored in the PET plastic hydrolysate by employing this bifunctional electrocatalyst for concurrent H2 and commodity chemical production. Our work may showcase the rational structural engineering of advanced electrocatalysts for multiple electrochemical applications.

Approaching well-dispersed MoS2 assisted with cellulose nanofiber for highly durable hydrogen evolution reaction

The agglomeration and low conductivity of molybdenum disulfide (MoS2) electrocatalysts restrict the presentation of its real intrinsic reaction activity, which leads to challenges for the high-performance hydrogen evolution reaction (HER). Herein, a well-dispersed and superhydrophilic/superaerophobic MoS2 catalyst with uniform three-dimensional conductive networks have been prepared assisted with cellulose nanofiber (CNF) and carboxylated multi-walled carbon nanotubes (cMWCNT). The resulted CNF/cMWCNT/MoS2 catalysts present a superhydrophilic/superaerophobic state with contact angles for water and bubble of 0° and 154.1° respectively. This structure effectively disperses MoS2 nanoparticles through uniform embeddedness and promotes gas-liquid mass transfer via wettability. Benefiting from these optimizations, the CNF/cMWCNT/MoS2 exhibits better HER performance and a low overpotential (154 mV @ 10 mA/cm2). Encourangingly, CNF/cMWCNT/MoS2 catalysts have a slight decay of 6.99 % at 10 mA/cm2 after 100 h, while the cMWCNT/MoS2 shows a decay of 35.83 %. This approach using natural CNF for well-dispersed catalysts provides a potential for high-performance HER electrode design.