Suppressing Hydrogen Evolution Research Articles

A self-assembled nanoporous polyelectrolytic interlayer for highly stable zinc metal anodes

Aqueous zinc-ion batteries (AZIBs) based on Zn metal anodes are promising candidates for next-generation energy storage due to their high performance, environmental friendliness, low cost, and high abundance. However, the excessive dendrite growth and continuous hydrogen evolution of Zn metal anodes in aqueous electrolytes severely deteriorate the electrochemical performance of AZIBs. Here, a highly stable Zn metal anode is designed by reconstructing its surface with a self-assembled nanoporous polyelectrolytic interlayer. This unique protective layer consisting of polyacrylic acid-zinc (PAAZn) nanospheres is highly hydrophilic and can act as a physical barrier to reduce the contact between Zn metal and water molecules, thus suppressing hydrogen evolution and Zn corrosion. Meanwhile, the unique nanostructures and chemical compositions of the PAAZn interlayer ensure fast Zn plating/stripping kinetics and facilitate the homogeneous growth of Zn deposits by redistributing Zn ion flux and local electric field at Zn/electrolyte interfaces. Therefore, symmetric cells based on the PAAZn-modified Zn metal anode (PAAZn@Zn) exhibited a significantly prolonged cycle life of 2,850 h and low voltage hysteresis. This work reports a uniquely designed nanoporous polyelectrolytic interlayer for highly reversible Zn metal anodes and provides a new strategy to enhance the electrochemical performance of AZIBs.

High energy efficiency and high discharge voltage of 2N-purity Al-based anodes for Al-air battery by simultaneous addition of Mn, Zn and Ga

As the anode material of Al air battery, 2N-purity (99 wt%) Al-based alloy has the disadvantages of low efficiency and low discharge voltage, which is attributed to the impurity of Fe in the 2N Al alloy. In this paper, the 2N Al-based anode with high energy efficiency and discharge voltage is successfully designed by adding Mn, Zn and Ga. The results show that adding Mn separately can inhibit hydrogen evolution corrosion but lead to the exfoliation corrosion of 2N Al. The addition of Ga, Mn and Zn together can suppress hydrogen evolution, decrease the weight loss of 2N Al alloy and significantly increase the output voltage and energy efficiency of an Al-air battery, which makes it possible to use cheap 2N Al as the anode of an Al-air battery.

A novel solvent system of polyamides achieves new application in ZIBs by aggregation induced Lewis acid-base centers

Dissolutions of the polymer in the chaotropic salts follow Hofmeister effect, and the aggregate of salts and solvents shows new influence of the Hofmeister effect. Here, we reveal the aggregation of ion–solvent in chaotropic salt solution catalyzes the formation of the exposed Lewis acid-base center and realizes the dissolution of polyamide (PA) macromolecules. The relationship between Hofmeister effect, aggregate chemistry and Lewis acid-base chemistry is examined from new perspective. And then, a new solvent system and phase conversion process are designed for polyamides. Finally, the applications of PA in ZIBs as coating layer and binder are realized. As an electrode coating, it can effectively inhibit hydrogen evolution, corrosion and dendrite problems and improve the cycle life (cycle over 1500 h at 0.5 mA cm−2). As a binder, the active material adhesion on current collector, uniformity and wettability of the electrode are improved. The assembled pouch-cell with PANI cathode shows a capacity of 150 mAh g−1 after 120 cycles. This work reveals the secret of controlled phase transformation of polyamide in saline solution from a new perspective. And this phase conversion method is simpler, greener and more environmentally friendly, which greatly accelerates the application of polyamide in the field of membrane science and binder science.

Ash‐Free Porous Carbon as the Negative Additive of Lead‐Acid Batteries and Supercapacitors

Herein, a simple method to prepare porous carbon that inhibits hydrogen evolution is used, which has enormous advantages for both capacitors and lead‐acid batteries. The quantitative filter paper spongy porous carbon (SQFPC) is successfully synthesized by the two‐step method. SQFPC displays a porous, spongy structure with a large specific surface area (1847 m2 g−1). In electrochemical tests, SQFPC exhibits high specific capacitance (244 F g−1 at 1 A g−1) and a capacitance retention rate of 72.5% at 40 A g−1. In addition, the capacity of the battery with 0.5 wt% SQFPC is improved by 57.6% at a discharge rate of 0.1C, and the cycle life under the high‐rate partial state of charge is 9.3 times that of the blank battery. The enhanced battery performance is related to the unique structure and surface functional groups of carbon, which speed up ion movement inside the battery and provide active sites for lead deposition.

Enhanced electrocatalytic nitrate reduction to ammonia on cobalt oxide nanosheets via multiscale defect modulation

The traditional Haber-Bosch process synthesizes ammonia subjecting to harsh process conditions and high energy consumption, and the nitrate pollution is a common environmental issue due to the excessive use of fertilizers. A sustainable and moderate nitrate electrocatalytic reduction to ammonia (NO3RR) was employed to achieve N-cycle, turning waste into treasure. Pre-density functional theory calculations forecast that Co3O4 will display optimal NO3RR performance among all the spinel cobalt-based catalysts. In this work, Co3O4/Co with unique interlaced nanosheets was fabricated through electrodeposition and calcination. Benefitting from the open-pore, defective nanosheet structure and modulated oxygen vacancy, the Co3O4/Co catalyst can accumulate more nitrate on activated sites and display excellent NO3RR properties in the neutral electrolyte (ammonia yield rate: 4.43 mg h−1 cm−2, Faradaic efficiency: 88.7 %). Theoretical calculations reveal that oxygen vacancy could enhance nitrate adsorption energy, suppress hydrogen evolution reaction, and weaken the rate-determining step of *NO → *HNO. Furthermore, the continuous NO3RR flow electrolyzer has been customized with Co3O4/Co electrocatalyst and it highly enlarges ammonia yield over one day, which could accelerate the NO3RR to commercial application.

Scalable Edge-Oriented Metallic Two-Dimensional Layered Cu2Te Arrays for Electrocatalytic CO2 Methanation.

Copper-based nanomaterials are compelling for high-efficient, low-cost electrocatalytic CO2 reduction reaction (CO2RR) due to their exotic electronic and structural properties. However, controllable preparation of copper-based two-dimensional (2D) materials with abundant catalytically active sites, that guarantee high CO2RR performance, remains challenging, especially on a large scale. Here, an in situ vertical growth of scalable metallic 2D Cu2Te nanosheet arrays on commercial copper foils is demonstrated for efficient CO2-to-CH4 electrocatalysis. The edge-oriented growth of Cu2Te nanosheets with tunable sizes and thicknesses is facilely attained by a two-step process of chemical etching and chemical vapor deposition. These active sites abounding on highly exposed edges of Cu2Te nanosheets greatly promote the electroreduction of CO2 into CH4 at a potential as low as -0.4 V (versus the reversible hydrogen electrode), while suppressing hydrogen evolution reaction. When a flow cell is employed to accelerate the mass transfer, the faradaic efficiency reaches ∼63% at an applied current density of 300 mA cm-2. These findings will provide great possibilities for developing scalable, energy-efficient Cu-based CO2RR electrocatalysts.

Study on Thermal Effect of Aluminum-Air Battery

The heat released from an aluminum-air battery has a great effect on its performance and operating life during the discharge process. A theoretical model was proposed to evaluate the resulting thermal effect, and the generated heat was divided into the following sources: anodic aluminum oxidation reaction, cathodic oxygen reduction reaction, heat production against the battery internal resistance, and hydrogen-evolution reaction. Quantitative analysis was conducted on each part, showing that all heat production sources increased with discharge current density. It should be noted that the heat caused by hydrogen evolution accounted for the most, up to 90%. Furthermore, the regulation strategy for inhibiting hydrogen evolution was developed by addition of hybrid additives to the electrolyte, and the hydrogen-evolution rate was greatly reduced by more than 50% as was the generated heat. This research has important guidance for the thermal effect analysis of aluminum-air batteries, together with control of the thermal management process by inhibiting hydrogen evolution, thus promoting their practical application.

Modulating Cation Migration and Deposition with Xylitol Additive and Oriented Reconstruction of Hydrogen Bonds for Stable Zinc Anodes

AbstractHighly reversible plating/stripping in aqueous electrolytes is one of the critical processes determining the performance of Zn‐ion batteries, but it is severely impeded by the parasitic side reaction and dendrite growth. Herein, a novel electrolyte engineering strategy is first proposed based on the usage of 100 mM xylitol additive, which inhibits hydrogen evolution reaction and accelerates cations migration by expelling active H2O molecules and weakening electrostatic interaction through oriented reconstruction of hydrogen bonds. Concomitantly, xylitol molecules are preferentially adsorbed by Zn surface, which provides a shielding buffer layer to retard the sedimentation and suppress the planar diffusion of Zn2+ ions. Zn2+ transference number and cycling lifespan of Zn∥Zn cells have been significantly elevated, overwhelmingly larger than bare ZnSO4. The cell coupled with a NaV3O8 cathode still behaves much better than the additive‐free device in terms of capacity retention.

Modulating Cation Migration and Deposition with Xylitol Additive and Oriented Reconstruction of Hydrogen Bonds for Stable Zinc Anodes.

Highly reversible plating/stripping in aqueous electrolytes is one of the critical processes determining the performance of Zn-ion batteries, but it is severely impeded by the parasitic side reaction and dendrite growth. Herein, a novel electrolyte engineering strategy is first proposed based on the usage of 100 mM xylitol additive, which inhibits hydrogen evolution reaction and accelerates cations migration by expelling active H2 O molecules and weakening electrostatic interaction through oriented reconstruction of hydrogen bonds. Concomitantly, xylitol molecules are preferentially adsorbed by Zn surface, which provides a shielding buffer layer to retard the sedimentation and suppress the planar diffusion of Zn2+ ions. Zn2+ transference number and cycling lifespan of Zn∥Zn cells have been significantly elevated, overwhelmingly larger than bare ZnSO4 . The cell coupled with a NaV3 O8 cathode still behaves much better than the additive-free device in terms of capacity retention.

Synchronous Dual Electrolyte Additive Sustains Zn Metal Anode with 5600 h Lifespan

AbstractDespite conspicuous merits of Zn metal anodes, the commercialization is still handicapped by rampant dendrite formation and notorious side reaction. Manipulating the nucleation mode and deposition orientation of Zn is a key to rendering stabilized Zn anodes. Here, a dual electrolyte additive strategy is put forward via the direct cooperation of xylitol (XY) and graphene oxide (GO) species into typical zinc sulfate electrolyte. As verified by molecular dynamics simulations, the incorporated XY molecules could regulate the solvation structure of Zn2+, thus inhibiting hydrogen evolution and side reactions. The self‐assembled GO layer is in favor of facilitating the desolvation process to accelerate reaction kinetics. Progressive nucleation and orientational deposition can be realized under the synergistic modulation, enabling a dense and uniform Zn deposition. Consequently, symmetric cell based on dual additives harvests a highly reversible cycling of 5600 h at 1.0 mA cm−2/1.0 mAh cm−2.

Synchronous Dual Electrolyte Additive Sustains Zn Metal Anode with 5600 h Lifespan.

Despite conspicuous merits of Zn metal anodes, the commercialization is still handicapped by rampant dendrite formation and notorious side reaction. Manipulating the nucleation mode and deposition orientation of Zn is a key to rendering stabilized Zn anodes. Here, a dual electrolyte additive strategy is put forward via the direct cooperation of xylitol (XY) and graphene oxide (GO) species into typical zinc sulfate electrolyte. As verified by molecular dynamics simulations, the incorporated XY molecules could regulate the solvation structure of Zn2+ , thus inhibiting hydrogen evolution and side reactions. The self-assembled GO layer is in favor of facilitating the desolvation process to accelerate reaction kinetics. Progressive nucleation and orientational deposition can be realized under the synergistic modulation, enabling a dense and uniform Zn deposition. Consequently, symmetric cell based on dual additives harvests a highly reversible cycling of 5600 h at 1.0 mA cm-2 /1.0 mAh cm-2 .

Synergy of regulating zinc electrodeposition and suppressing hydrogen evolution by functional coating layer for highly reversible zinc anode

The Zn metal anode for aqueous Zn-ion batteries (AZIB) has attracted intensive attention owing to its high theoretical capacity and low cost. However, two intrinsic problems, including hydrogen evolution induced by low redox overpotential and unordered dendrite growth owing to its physiochemical properties, can contribute to futile consumption of Zn anode and safety failure, which hinder the practical application of AZIB. Herein, a strategy of introducing organic protective layer (P3HT) is demonstrated to be effective to segregate electrode and electrolyte for prolonged cycling life. The P3HT with hydrophobic property can block the access of H2O, benefit the Zn2+ transport, and regulate the electrical field distribution and Zn2+ flux field distribution around Zn surface for homogeneous Zn metal deposition. The optimized OPZn anode can present excellent stripping/plating cycles (1000 h at 1 mA cm−2 for 1 mAh cm−2; 900 h at 3 mA cm−2 for 1 mAh cm−2), deliver stable rate performance, and enable good full OPZn|HCNF battery. This work provides a novel method for suppression of hydrogen evolution and guidance of uniform Zn ions deposition during the electrochemical process.

Rare-earth La-doped VS2−xfor electrochemical nitrate reduction to ammonia

A rare-earth La-doped VS2−x is reported as an effective catalyst for electrocatalytic nitrate-to-ammonia conversion, which is attributed to the synergy of La-dopants and S-vacancies to promote NO3RR and suppress hydrogen evolution.

Simultaneous tailoring of hydrogen evolution and dendrite growthviaa fertilizer-derived additive for the stabilization of the zinc anode interface

A highly effective strategy to regulate Zn nucleation and suppress hydrogen evolution in Zn-ion batteries using a fertilizer-derived additive is reported. Mechanism by which the fertilizer-derived additive modulates the Zn interface.

Enhancing electrochemical performance and stabilizing zinc anode in mild acidic electrolyte using combined additive

Rechargeable zinc-based batteries having aqueous electrolytes are renowned as promising alternatives for large scale energy storage systems (ESSs). However, in mild acidic electrolytes, zinc anodes pose several issues that have yet to be overcome. For tackling the major difficulties of zinc anodes, electrolyte engineering is the most practical and cost-effective strategy. Notwithstanding the broad variety of mechanisms associated with different electrolyte additives, the function of a single additive is straightforward. Finding combined additives with broader functionalities and greater efficacy is crucial. In this work, the combination of ionic liquid (IL) 1-butyl-1-methylpyrrolidinium dicyanamide ([BMPY][DCN]) and ethylene glycol (EG) as additives in an aqueous electrolyte 3 M ZnSO4 proves to be an effective strategy for simultaneously enhancing both zinc dissolution and deposition. IL significantly enhances zinc (Zn) dissolution and deposition while EG plays an important role in suppressing hydrogen evolution reaction (HER)and corrosion. Thus, 13.50 % improvement in capacity is achieved by the mixed additive EG + IL/ZnSO4 compared with the 3 M ZnSO4 electrolyte. In the Zn//Zn symmetrical system at 2 mA cm−2, the mixed additive greatly augments the cyclability of zinc, reaching over 400 h while maintaining excellent coulombic efficiency (CE). In-situ XAS and FT-EXAFS analyses confirm the high activities of both zinc oxidation/reduction in the mixed additive electrolyte. Results demonstrate that EG + IL/ZnSO4 can be applied to increase the cyclability of aqueous zinc-based batteries while sustaining high performance.

Dual‐Site Functionalization on Supported Metal Monolayer Electrocatalysts for Selective CO2 Reduction (Adv. Energy Mater. 3/2023)

CO2 Electroreduction In article number 2203138, Zhonglong Zhao and Gang Lu predict that noble metal monolayers supported by transition metal carbides (TMCs) and nitrides (TMNs) could be selective catalysts for the carbon dioxide reduction reaction with suppressed hydrogen evolution reaction. Dual-site functionalization induced by antibonding interactions between hydrogen and the TMC/TMN substrates is identified, which can circumvent energy scaling relations and enable active, selective, and robust CO2 electroreduction.

Main-group indium single-atom catalysts for electrocatalytic NO reduction to NH3

In single atoms confined in amorphous MoO3(In1/a-MoO3) are reported to be an efficient catalyst for NO electroreduction to NH3, attributed to the ability of single-site In to inhibit hydrogen evolution and optimize NO-to-NH3hydrogenation energetics.

Two-dimensional MBene: a comparable catalyst to MXene for effective CO2RR towards C1 products.

Electrochemical CO2 reduction reaction (CO2RR) to high-value-added products is one of the most promising strategies for mitigating the greenhouse effect and energy shortage. Two-dimensional (2D) MXene materials are regarded as promising catalysts for electrocatalysis, and the boron-analogs of MXenes, 2D transition metal borides (MBenes), may exhibit superior CO2RR performance owing to their unique electronic properties. Herein, a novel 2D transition metal boride, MoB, is theoretically evaluated as a potential catalyst for the CO2RR by comparing it with traditional Mo2C. MoB shows metallic nature and exhibits excellent electrical conductivity. MoB can effectively activate CO2 with a larger interaction energy of -3.64 eV than that of Mo2C. Both density of states and charge difference density reveal a significant charge transfer from MoB to CO2. MoB shows higher catalytic selectivity due to its inhibited hydrogen evolution reaction and low reaction energy for the CO2RR. At potentials more negative than -0.62 V, the CO2RR on MoB becomes a high-throughput reaction process towards CH4. This work discovered that MoB exhibited comparable CO2RR performance to Mo2C and forecasted MBenes as promising catalysts for electrocatalysis.

A new selection criterion for voltage windows of aqueous zinc ion hybrid capacitors: achieving a balance between energy density and cycle stability

Connected link between by-products and potential windows, with basic zinc sulfate from ZHSs inhibiting hydrogen evolution to protect electrode material. Results show balancing energy density and cycling stability in ZHSs with the proposed criterion.

Reconstruction of Electric Double Layer for Long‐Life Aqueous Zinc Metal Batteries

AbstractAqueous rechargeable Zn metal batteries (AZMBs) have attracted widespread attention due to their intrinsic high volumetric capacity and low cost. However, the unstable Zn/electrolyte interface causes Zn dendrite growth and side reactions, resulting in poor Coulombic efficiency and unsatisfactory lifespan. Herein, a SiO2 reinforced‐sodium alginate (SA) hybrid film is designed to regulate solid–liquid interaction energy and spatial distribution of all species in the electric double layer (EDL) near the Zn electrode. The unique interfacial layer gives rise to a uniform distribution of Zn2+ in the Helmholtz layer through solvation sheath modulation. Moreover, theoretical calculations show that the SO42− anions and free‐water are substantially reduced in the Helmholtz layer, effectively suppressing hydrogen evolution reaction and formation of by‐products through strong charge repulsion and hydrogen bond fixing of free‐water. The reconfigured EDL not only ensures homogenous and fast Zn2+ transport kinetics for dendrite‐free Zn deposition, but also eliminates interface parasitic side reactions. The Zn@SiO2‐SA electrode enables excellent cycling stability of symmetrical cells and high‐loading full AZMBs with a lifespan over 3000 h and an areal capacity of 2.05 mAh cm−2, thus laying a solid basis for realizing practical AZMBs.