Hydrogen Evolution Reaction In Neutral Media Research Articles

Single-Atom Pt Embedded in Defective Layered Double Hydroxide for Efficient and Durable Hydrogen Evolution.

Electrocatalysis in neutral conditions is appealing for hydrogen production by utilizing abundant wastewater or seawater resources. Single-atom catalysts (SACs) immobilized on supports are considered one of the most promising strategies for electrocatalysis research. While they have principally exhibited breakthrough activity and selectivity for the hydrogen evolution reaction (HER) electrocatalysis in alkaline or acidic conditions, few SACs were reported for HER in neutral media. Herein, we report a facile strategy to tailor the water dissociation active sites on the NiFe LDH by inducing Mo species and an ultralow single atomic Pt loading. The defected NiFeMo LDH (V-NiFeMo LDH) shows HER activity with an overpotential of 89 mV at 10 mA cm-2 in 1 M phosphate buffer solutions. The induced Mo species and the transformed NiO/Ni phases after etching significantly increase the electron conductivity and the catalytic active sites. A further enhancement can be achieved by modulating the ultralow single atom Pt anchored on the V-NiFeMo LDH by potentiostatic polarization. A potential as low as 37 mV is obtained at 10 mA cm-2 with a pronounced long-term durability over 110 h, surpassing its crystalline LDH materials and most of the HER catalysts in neutral medium. Experimental and density functional theory calculation results have demonstrated that the synergistic effects of Mo/SAs Pt and phase transformation into NiFe LDH reduce the kinetic energy barrier of the water dissociation process and promote the H* conversion for accelerating the neutral HER.

3D Self‐Supported Catalyst with Multiple Active Components for Efficient Neutral Hydrogen Evolution Reaction

AbstractUp to now, the hydrogen evolution reaction (HER) are mainly investigated in strong acidic/alkaline electrolytes. However, the HER in extreme conditions shows several drawbacks, including the corrosion of electrolyzer, water pollution, and the use of expensive anion/cation exchange membranes. The HER in neutral media is desirable to address these issues. Nevertheless, the neutral HER still faces a great challenge due to its slow kinetics. Herein, we report a plasma‐assisted approach to synthesize an efficient electrocatalyst (denoted as 3D P−Mo−NiFe LDH) with multiple active components (Ni nanoparticles, Ni3Mo alloy nanoparticles, oxygen vacancies, and molybdate‐incorporated NiFe layered double hydroxide nanosheets) supported on Cu2+1O nanorod array for neutral HER. The 3D hierarchical nanostructure can endow the catalyst with enhanced mass transfer and more exposed active sites, while the multiple active components can accelerate the HER kinetics in neutral media. As expected, the 3D P−Mo−NiFe LDH exhibits outstanding HER activity (24 mV@10 mA cm−2) and excellent stability (up to 200 h) in 1 M phosphate buffer solution (PBS).

Facile Fabrication of Robust Hydrogen Evolution Electrodes under High Current Densities via Pt@Cu Interactions

AbstractDurable and efficient hydrogen evolution reaction (HER) electrocatalysts that can satisfy industrial requirements need to be developed. Platinum (Pt)‐based catalysts represent the benchmark performance but are less studied for HER under high current densities in neutral electrolytes due to their high cost, poor stability, and extra water dissociation step. Here a facile and low‐temperature synthesis for constructing “blackberry‐shaped” Pt nanocrystals on copper (Cu) foams with low loading as self‐standing electrodes for HER in neutral media is proposed. Optimized hydrogen adsorption free energy and robust interaction induced by charge density exchange between Pt and Cu ensure the efficient and robust HER, especially under high current densities, which are demonstrated from both experimental and theoretical approaches. The electrode exhibits small overpotentials of 35 and 438 mV to reach current densities of ‐10 and ‐1000 mA cm−2, respectively. Meanwhile the electrode illustrates outstanding stability during chronoamperometry measurement under high current densities (‐100 to ‐400 mA cm−2) and 1000 cycles linear sweep voltammetry tests reaching ‐1000 mA cm−2. This study provides new design strategies for self‐standing electrocatalysts by fabricating robust metal–metal interactions between active materials and current collectors, thus facilitating the stable function of electrodes for HER under technologically relevant high current densities.

A confinement strategy for stabilizing two-dimensional carbon / CoP hybrids with enhanced hydrogen evolution

Two-dimensional carbon/CoP hybrids catalysts usually exhibit extraordinary performance especially in hydrogen evolution reaction (HER) application because of their unique morphology which bring unique physical and chemical properties. Although Co-doped zeolitic imidazolate framework nanoleaf (Co-ZIF-L) is quite attractive as carbon-based catalyst precursor, carbonization and phosphorization processes would normally induce Co-ZIF-L derived CoP/N-doped carbon (CoP-NC) catalyst to occur structural collapse due to the shrinkage stress and strong reducibility of PH3, seriously restricting the structural advantage of these catalysts. To this end, a carbon-shell confinement strategy by polydopamine (PDA) is developed to improve the structural stability of these catalysts. The precursor that Co-ZIF-L coated with PDA (Co-ZIF-L@PDA) has a more stable structure, which makes the electrocatalyst CoP-NC possess componential advantage and the merits of two-dimensional structure. The resultant CoP-NC exhibits enhanced activity and good stability for pH-universal HER. The overpotentials of CoP-NC at the current density of 10 mA cm−2 are 145 mV in 0.5 M H2SO4 solution and 167 mV in 1 M KOH solution. Additionally, the electrocatalyst CoP-NC displays comparable activity and stability for HER in neutral media as well.

Underwater superaerophobic Ni nanoparticle-decorated nickel–molybdenum nitride nanowire arrays for hydrogen evolution in neutral media

Abstract Electrochemical water splitting into hydrogen and oxygen in neutral electrolytes has great significance for future energy supply security, potentially offering a pathway for H2 generation from seawater. However, the electrocatalytic hydrogen evolution reaction (HER) generally occurs at low rates in neutral solutions due to the low proton concentration in such media. Herein, we fabricated a novel HER catalyst capable of efficient H2 evolution in water at neutral pH, comprising a nickel-molybdenum nitride nanowire array modified with metallic Ni nanoparticles (Ni/NiMoN). The entire Ni/NiMoN array was supported on a Cu foam. The Ni nanoparticles promoted the dissociation of adsorbed water to enhance the supply of protons in the neutral electrolyte, whilst the nanowire array imparted the electrode surface with underwater superaerophobic properties, thus allowing H2 gas bubbles to detach from the electrode in a facile manner. On the basis of the synergies realized between the different electrode components, the Ni/NiMoN nanowire array electrode offered exceptional HER performance, with an overpotential of only 37 mV at a current density of 10 mA cm−2 in a neutral electrolyte. Results guide the development of next-generation earth-abundant element electrocatalysts for HER in neutral media.

Potential‐Cycling Synthesis of Single Platinum Atoms for Efficient Hydrogen Evolution in Neutral Media

AbstractSingle‐atom catalysts (SACs) have exhibited high activities for the hydrogen evolution reaction (HER) electrocatalysis in acidic or alkaline media, when they are used with binders on cathodes. However, to date, no SACs have been reported for the HER electrocatalysis in neutral media. We demonstrate a potential‐cycling method to synthesize a catalyst comprising single Pt atoms on CoP‐based nanotube arrays supported by a Ni foam, termed PtSA‐NT‐NF. This binder‐free catalyst is centimeter‐scale and scalable. It is directly used as HER cathodes, whose performances at low and high current densities in phosphate buffer solutions (pH 7.2) are comparable to and better than, respectively, those of commercial Pt/C. The Pt mass activity of PtSA‐NT‐NF is 4 times of that of Pt/C, and its electrocatalytic stability is also better than that of Pt/C. This work provides a large‐scale production strategy for binder‐free Pt SAC electrodes for efficient HER in neutral media.

Potential-Cycling Synthesis of Single Platinum Atoms for Efficient Hydrogen Evolution in Neutral Media.

Single‐atom catalysts (SACs) have exhibited high activities for the hydrogen evolution reaction (HER) electrocatalysis in acidic or alkaline media, when they are used with binders on cathodes. However, to date, no SACs have been reported for the HER electrocatalysis in neutral media. We demonstrate a potential‐cycling method to synthesize a catalyst comprising single Pt atoms on CoP‐based nanotube arrays supported by a Ni foam, termed PtSA‐NT‐NF. This binder‐free catalyst is centimeter‐scale and scalable. It is directly used as HER cathodes, whose performances at low and high current densities in phosphate buffer solutions (pH 7.2) are comparable to and better than, respectively, those of commercial Pt/C. The Pt mass activity of PtSA‐NT‐NF is 4 times of that of Pt/C, and its electrocatalytic stability is also better than that of Pt/C. This work provides a large‐scale production strategy for binder‐free Pt SAC electrodes for efficient HER in neutral media.

Silica-Polypyrrole Hybrids as High-Performance Metal-Free Electrocatalysts for the Hydrogen Evolution Reaction in Neutral Media.

Constructing inorganic-organic hybrids with superior properties in terms of water adsorption and activation will lead to catalysts with significantly enhanced electrocatalytic activity in the hydrogen evolution reaction (HER) in environmentally benign neutral media. Herein, we report SiO2 -polypyrrole (PPy) hybrid nanotubes supported on carbon fibers (CFs) (SiO2 /PPy NTs-CFs) as inexpensive and high-performance electrocatalysts for the HER in neutral media. Because of the strong electronic interactions between SiO2 and PPy, the SiO2 uniquely serves as the centers for water adsorption and activation, and accordingly promotes the HER. The metal-free SiO2 /PPy NTs-CFs displayed high catalytic activity in the HER in neutral media, such as a low onset potential and small Tafel slope, as well as excellent long-term durability.

Silica–Polypyrrole Hybrids as High‐Performance Metal‐Free Electrocatalysts for the Hydrogen Evolution Reaction in Neutral Media

AbstractConstructing inorganic–organic hybrids with superior properties in terms of water adsorption and activation will lead to catalysts with significantly enhanced electrocatalytic activity in the hydrogen evolution reaction (HER) in environmentally benign neutral media. Herein, we report SiO2–polypyrrole (PPy) hybrid nanotubes supported on carbon fibers (CFs) (SiO2 /PPy NTs–CFs) as inexpensive and high‐performance electrocatalysts for the HER in neutral media. Because of the strong electronic interactions between SiO2 and PPy, the SiO2 uniquely serves as the centers for water adsorption and activation, and accordingly promotes the HER. The metal‐free SiO2 /PPy NTs–CFs displayed high catalytic activity in the HER in neutral media, such as a low onset potential and small Tafel slope, as well as excellent long‐term durability.