Electrochemical Hydrogen Generation Research Articles

Electrochemical Oxidation of Ethanol and Methanol at Rh@Pt Catalysts at 80 °C in Proton Exchange Membrane (PEM) Cells

Efficient oxidation of ethanol to carbon dioxide is crucial for the development of sustainable electrochemical generation of power and hydrogen from bioethanol. However, high anode overpotentials and partial oxidation to acetaldehyde and acetic acid result in low efficiencies and waste management issues. Bimetallic Rh-Pt catalysts have shown enhanced activities and CO2 production in aqueous electrolytes, but not in proton exchange membrane (PEM) cells. In this work Rh@Pt core–shell catalysts, prepared from commercial carbon-supported Rh, have been evaluated in both aqueous H2SO4 and PEM cells. Cyclic voltammetry of aqueous methanol and ethanol has shown that the catalytic activity of the Pt shell is increased by the compressive strain induced by the Rh core, and that there is also a significant bifunctional effect at low Pt coverages. In PEM cells, these effects also increase selectivity for cleavage of the C–C bond of ethanol to produce CO2, which will enhance the efficiencies of ethanol fuel and electrolysis cells for producing power and hydrogen, respectively. Deposition of 0.5 monolayers of Pt onto the Rh core produced the highest CO2 yields at the lowest anode overpotentials, while higher coverages of Pt increased performances and CO2 yields at higher potentials.

Astonishing performance of zinc iron sulfide with MoS2 composite in allium-shaped structure for comprehensive alkaline water splitting

Electrochemical water splitting offers a promising avenue for producing clean hydrogen fuel, essential for a sustainable energy landscape. A highly efficient catalyst, featuring a one-dimensional structure, has been synthesized by combining zinc iron sulfide with molybdenum disulfide (ZFSMS) on a nickel foam substrate. This synthesis method utilizes a simple yet effective hydrothermal approach tailored for efficient water splitting. By carefully engineering the interface between zinc iron sulfide and molybdenum disulfide, the electronic conductivity of the catalyst is significantly boosted, enhancing its catalytic performance. The resulting hybrid, ZFSMS, exhibits remarkable electrocatalytic efficiency with minimal overpotentials. Specifically, overpotentials of 130 mV and 220 mV are recorded for the oxygen evolution reaction at 20 mA cm−2 and 50 mA cm−2, respectively. Moreover, for the hydrogen evolution reaction, overpotentials of 145 mV and 257 mV are observed at 10 mA cm−2 and 40 mA cm−2, respectively, in a 1.0 M potassium hydroxide solution. Notably, the ZFSMS-based electrolyzer operates at a low voltage of 1.5 V at 10 mA cm−2, underscoring its efficiency in facilitating electrochemical hydrogen generation. This catalyst good candidate for advancing green hydrogen production, contributing to the progress of sustainable and clean hydrogen fuel production methods.

Design and synthesis of heteroleptic Ni(II) dipyrrin complexes for electrochemical proton reduction reactions: Cyclic voltammetric and theoretical studies

The effect of nuclearity on electrochemical hydrogen generation using new heteroleptic Ni(II) complexes containing redox-active dipyrrin and dithiocarbamate ligands has been described. Complexes 1–2 have been meticulously characterized by spectroscopic studies (ESI-MS, IR, 1H, 13C NMR, UV–vis) and their structures unambiguously confirmed by X-ray single crystal analyses. Electrocatalytic properties of the complexes toward hydrogen evolution reaction have been investigated by cyclic voltammetric studies in an organic medium in the presence of acetic acid as a weak proton source. Notably, complexes 1 and 2 produce H2 via doubly reduced Ni(II) species i.e. Ni(0) in the presence of acetic acid. Further, these complexes exhibited significant electrocatalytic activity (TOF: 264 (1) and 650 s−1 (2). Controlled potential electrolysis established a minimum Faradaic efficiency of 92 (1) and 96 % (2). Complex 2 exhibited higher turnover frequency relative to 1, while 1 showed lower overpotential (0.35 V) in comparison to 2 (0.45 V). The stability of the complexes and the amount of produced H2 has been investigated by bulk electrolysis study. A tentative mechanism (ECEC; E, electrons and C, chemical steps) and involved intermediate species for the proton reduction reaction for 1 has been established by theoretical studies.

Rapid CO2 laser treatment of Pt–Fe MOF for efficient electrochemical hydrogen evolution reaction

The quest for efficient hydrogen production via electrochemical water splitting has led to extensive research on catalytic materials. This work focuses on enhancing the catalytic functionality of metal-organic frameworks (MOFs) by incorporating platinum (Pt) to improve the performance of the hydrogen evolution reaction (HER). Fe-based MOFs mixed with platinum precursors were altered through laser treatment, which caused considerable changes in their structure and catalytic activity in just 3 min. This was achieved without the need for vacuum or an inert atmosphere. Characterization techniques including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and electrochemical measurements were used to characterize the synthesized materials. The laser-treated Pt–Fe MOF demonstrated outstanding HER performance with 3.5 wt% Pt content, outperforming commercial 20 wt% Pt/C catalysts, and exhibiting good stability even after prolonged cycling. These results highlight the potential of laser-treated MOFs for efficient and cost-effective electrochemical hydrogen generation.

Synthesis of bimetal-decorated N-doped carbon nanoparticles for enhanced oxygen evolution reaction

Electrochemical hydrogen generation from the most plausible splitting water is severely hindered by OER (oxygen evolution reaction). Hence, the Fe4Co6@NDC amorphous sheet-like lamellar potential electrocatalyst prepared through simple solvothermal synthesis towards OER with low overpotential 307 mV @ 10 mA cm−2, Tafel slope of −55 mV dec-1 and turnover frequency of 0.0396 s−1, compared to 393 mV, Tafel slope of −81 mV dec-1, and a turnover frequency of 0.0136 s−1 at an IrO2 on an inert glassy carbon electrode, under the same conditions in 1 M KOH. The iron: cobalt adjacent ratio (4:6) could give a cooperative synergistic effect for OER, further nitrogen-doped carbon substrate (NDC) offers even metal anchoring sites has provided higher ECSA of 10.202 cm2 and also provides low resistive (5.6 Ω) material. Full cell water splitting Fe4Co6@NDC/NF (anode)//PtC/NF (cathode) with cell potential 1.58 V and the same setup will be used with perennial solar energy source only consumes 1.57 V enhanced hydrogen generation. We anticipate that the developed Fe4Co6@NDC electrocatalyst will be used as a formidable OER catalyst for a clean electrochemical energy conversion process.

Accessible Ni‐Fe‐Oxalate Framework for Electrochemical Urea Oxidation with Radically Enhanced Kinetics

AbstractUrea oxidation reaction (UOR) has been utilized to substitute the oxygen evolution reaction (OER), to escalate the energy conversion efficiency in electrochemical hydrogen generation processes with denitrification of widespread urea in wastewater. This study reports breakthroughs in Ni‐based UOR electrocatalysts, particularly with NiFe oxalate (O‐NFF), derived from Ni3Fe alloy foam with prismatic nanostructures and elevated surface area. The O‐NFF achieves cutting‐edge performances, representing 500 mA cm−2 of current density at 1.47 V RHE and exceptionally low Tafel slope of 12.1 mV dec−1 (in 1 m KOH with 0.33 m urea). X‐ray photoelectron/absorption spectroscopy (XPS/XAS) coupled with density functional theory calculations unveil that oxalate ligands induce charge deficient Ni center, promoting stable urea‐O adsorption. Furthermore, Fe dopants enhance oxalate‐O charge density and H‐bond strength, facilitating C‐N cleavage for N2 and NO2− formation. The extraordinary UOR kinetics by the tandem effects of oxalate and Fe prevent Ni over‐oxidation, corroborated by operando XAS, minimizing OER interference. It agrees with an adaptive reconstruction to Fe‐doped β‐NiOOH on top surface in extended urea electrolysis with marginal loss in UOR kinetics. This findings shed light to bimetal‐organic‐framework as (pre)catalysts to improve industrial electrolytic H2 production.

Realizing ultralow overpotential during electrochemical hydrogen generation through photoexcitation of chromium disulphide

Designing efficient electrocatalysts for hydrogen generation is desirable for electrochemical water splitting and fuel cells as they are a part of clean and sustainable energy system. Here, we are reporting the utilization of clean method for the production of platinum deposited chromium disulphide (CrS2) particles and their application for hydrogen generation via photo-assisted electrochemical water splitting. Photoelectrochemical studies of CrS2 show a close to zero onset potential, ultralow overpotential (8.3 mV), small Tafel slope (54 mV/decade), and low impedance (1.8 Ω) in acidic media. The chronoamperometric study of prepared catalyst reveals that it is sustainable as having a long-term stability. The post electrochemical study of electrode surface reveal the presence of traces of Pt deposited over CrS2. The detailed compositional analysis of electrolyte has also been performed. This study opens up a pathway for electrochemically modifying the composition of the catalysts for harnessing their potential as efficient electrocatalyst during water splitting.

Electrochemical hydrogen generation by a four-coordinate square-planar Ni(ii) complex with an N2P2-type ligand

Electrochemical and DFT studies on electrocatalytic hydrogen production in Ni(ii) complexes of N2P2-type ligands with/without amino group showed that the amino group plays a role in increasing basicity of pyridyl N atom as well as proton capturing.

Doping induced mixed polytypic interfaces of MoS2 for superior electrocatalytic hydrogen evolution

Metallic 1Tphase of MoS2 is desirable for accelerating electrochemical hydrogen generation from water due to its excellent electrical conductivity. However, it is challenging to synthesize stable 1T-MoS2 on a large scale using conventional chemical or physical routes. Here in, we report highly durable Mn-doping assisted in-plane 1T/2H mixed phases of MoS2 synthesized by a simple one-step hydrothermal method. The Mn-doping not only results in a favourable electronic modification in the host lattice but also in a structural evolution from 2H (trigonal prismatic) to 1T (octahedral) phase through sulfur-plane gliding with additional defects. The 1T/2H interfaces exhibit more active sites for hydrogen evolution reaction (HER) than its bulk 2H-counterpart. The developed electrode shows relatively low overpotential of 95 mV at a current density of 10 mA/cm2 and a low Tafel slope of 72 mV/dec in 0.5 M H2SO4. In addition, Density Functional Theory based calculations also support that Mn-doping in pristine 2H-MoS2 encourages a structural phase separation. Locally hybridized d-orbitals of Mn induce the formation of 2H/1T interfaces. It results in the delocalization of electrons, and thus facilitates the hydrogen adsorption and desorption process, better than the 2H phase.

Study of CuO/TiO2/Polyindole (CTPIN) electrocatalyst in membraneless electrolyzer for solar hydrogen generation

Efficient electrocatalysts are indispensable for promoting the hydrogen evolution reaction (HER). Existing electrocatalysts are limited by sluggish HER kinetics, higher over potential leading to greater energy demand, instability over time, and low tolerance to impurities. These challenges lead to a lower solar-to-hydrogen conversion efficiency of 2.46% using MoS2 electrocatalyst in authors’ previous research work. Mixed metal oxide/conducting polymer nanocomposites have shown great potential for use in hydrogen evolution reaction (HER) reactors due to their high surface area, excellent catalytic activity, and stability in acidic and alkaline environments. A major requirement for suitable electrocatalyst is a low overpotential for hydrogen evolution, a high tolerance to impurities and a long-term durability which makes it more efficient than traditional electrocatalysts. With this brief background, the present work focuses on the application of CuO/TiO2/Polyindole (CTPIN) nanocomposite synthesized with the help of two-step process involving microemulsion and oxidative polymerization techniques. The resulting material was characterized using miscellaneous physicochemical techniques. HRTEM analysis clearly demonstrates the formation of CTPIN nanocatalysts with ultrasmall particle sizes of 10–30 nm. The nickel strip was coated with CTPIN nanoparticles was used as cathode for generating solar hydrogen through membraneless electrochemical water splitting. Membraneless electrolyzers offer a promising and cost-effective substitute to traditional electrolyzers, enabling efficient electrochemical hydrogen generation. At a radiation intensity of 320 W/m2 and under normal working conditions, the CTPIN nanocomposite demonstrated a solar-to-hydrogen generation efficiency of 3.43% which is greater than previous results obtained using MoS2. The CTPIN electrocatalyst has a high potential for electrocatalytic solar hydrogen generation. The CTPIN electrocatalyst could make it possible to produce hydrogen from clean and renewable energy source.

Water Splitting as an Alternative for Electrochemical Hydrogen and Oxygen Generation: Current Status, Trends, and Challenges

Water splitting technology is an innovative strategy to face the dependency on fossil fuels and, at the same time, address environmental pollution issues. Electrocatalysts seem to be the better option to improve water separation efficiency and satisfy the commercial-scale demand for hydrogen. Therefore, the design and fabrication of heterostructures with a high affinity for achieving water splitting have been proposed. In this review, the application of several electrocatalysts for hydrogen and oxygen evolution reactions is presented and discussed in detail. A review of the recent advances in water separation using noble metals such as Pt-, Ir-, and Ru-based electrodes is presented, followed by a highlighting of the current trends in noble-metal-free electrocatalysts and novel preparation methods. Furthermore, it contemplates some results of a hybrid organic molecule–water electrolysis and photoelectrochemical water splitting. This review intends to give insight into the main trends in water splitting and the barriers that need to be overcome to further boost the efficiency of the main hydrogen and oxygen generation systems that ultimately result in large-scale applications. Finally, future challenges and perspectives are addressed, considering all the novelties and the proposed pathways for water splitting.

Research on the electrochemical degradation and hydrogen generation of Fraxinus mandshurica by polyoxometalate

ABSTRACT The efficient utilization of wood waste is important for protecting the environment and solving the energy shortage problem. Taking Fraxinus mandshurica (FM) as an example, polyoxometalate (POM) was used as a catalyst for cyclic redox in an H-type electrolytic cell, where wood was oxidized to valuable small-molecule chemicals at the anode and hydrogen was generated at the cathode. The system successfully recycles energy, simultaneously converting biomass to chemical and electrical to hydrogen. Furthermore, the effects of various factors on the reaction were also investigated to obtain the optimal electrochemical conversion results for wood waste. At the optimal conditions, the FM degradation rate of 56.1%, with aromatic organic and carbonyl compounds as the main products, and the average Faraday efficiency of hydrogen generation can reach 93%, saving about 40% of energy consumption compared to water electrolysis at 0.1 A cm−2. Therefore, this electrochemical conversion method provides a new potential pathway for the application of wood waste.

Bioreactors and biophoton-driven biohydrogen production strategies

Given the current issues with global warming and rising greenhouse gas emissions, biohydrogen is a viable alternative fuel option. Technologies to produce biohydrogen include photo fermentation, dark fermentation, direct and indirect bio-photolysis, and two-stage fermentation. Biological hydrogen generation is a green and promising technique with mild reaction conditions and low energy consumption compared to thermochemical and electrochemical hydrogen generation. To optimize hydrogen gas output using this method, the activity of hydrogen-consuming bacteria should be restricted during the production stages of hydrogen and acetate to prevent or limit hydrogen consumption. Raw material costs, poor hydrogen evolution rates, and large-scale output are the main limitations in biological hydrogen generation systems. Organic wastes would be the most preferred target feedstock for hydrogen fermentation, aside from biodegradable wastes, due to their high amount and simultaneous waste treatment advantage. This study examined the three primary methods for converting waste into bio-hydrogen: microbial electrolysis cell, thermochemical gasification, and biological fermentation, from both a technological and environmental standpoint. The effectiveness and applicability of these bioprocesses in terms of aspects influencing processes and their constraints are discussed. Alternative options for improving process efficiency, like microbial electrolysis, bio-augmentation, and multiple process integration, are also considered for industrial-level applications. Biohydrogen generation might be further enhanced by optimization of operating conditions and adding vital nutrients and nanoparticles. Cost reduction and durability enhancement are the most significant hindrances to fuel-cell commercialization. This review summarizes the biohydrogen production pathways, the impact of used organic waste sources, and bacteria. The work also addresses the essential factors, benefits, and challenges.

Rapid fabrication of CuMoO4 nanocomposites via electric field assisted pulsed-laser ablation in liquids for electrochemical hydrogen generation

Transition–metal-doped electrocatalysts are considered as low-cost alternatives of Pt and RuO2 electrocatalysts for large scale electrochemical generations of hydrogen and oxygen, respectively. Although, chemical synthesis, typically adopted to produce these electrocatalysts, is scalable but hazardous by-products and chemical wastes create growing environmental concerns. Here, we developed a single step, single pot, and environmentally friendly physical approach of electric field-assisted pulsed laser ablation in liquid for the synthesis of colloidal solution of pure CuMoO4 (CMO) electrocatalysts. The entire process took few minutes and did not involve or generate any chemical. A pulsed picosecond laser was used to ablate MoS2 target at the solid-liquid interface to generate spatially confined plasma plume. Two parallel electrodes (copper sheets) were mounted around the plasma plume to modulate the plasma parameters, control the reactions at the plasma-liquid interface, and simultaneously inject copper ions from the electrode to the laser-produced plasma (LPP) for the generation of CMO. nanoparticles. Surprisingly, we observed that by varying the applied electric field, we can efficiently control the size, shape, crystallinity, morphology, and composition of as produced CMO nanocomposites and enhance their hydrogen evolution reaction (HER) performance. The characterization results proves that the introduction of applied electric field during the laser ablation process significantly change the morphology of as-prepared nanomaterials, and the shape of these nanomaterials were spherical, spindle and cuboid for MoS2, CuO and CMO respectively. Among all the fabricated electrocatalysts, CMO-60 is the best HER performer in alkaline medium, while MoS2 and CuO nanoparticles were the worse. For CMO-60 sample, only 440 mV overpotential required to reach the current density of 10 mA/cm2 and as well as posess good stability. We found that electrocatalysts produced at a higher electric field have higher contents of copper and oxygen leading to a superior HER activity. The developed approach can be applied for the synthesis of other electrocatalysts for a range of chemical reactions.

Free standing MoSe2 growth on porous Graphite-Like membranes for water splitting

Clean hydrogen made from water-splitting through the hydrogen evolution reaction (HER) is important for sustainability and reducing pollution. Exploration of high-efficiency Pt-free electrochemical catalysts for HER is considered a great challenge for the development of sustainable and carbon dioxide-free energy conversion systems.For that, electrocatalytic electrodes made of self-standing binder-free materials have been extensively employed in hydrogen production. Herein, the gelatin and graphene oxide cryogels were cryogeleted and then carbonized to create a unique interconnecting macroporous conducting carbon membrane. The conducting membrane is employed as a substrate for growing MoSe2nanosheets vertically using a simple solvothermal process. The electrochemical performance of the self-standing MoSe2-based heterogeneous binder-free materials was successively evaluated for HER.The excellent electrochemical hydrogen generation exhibited a low onset potential of −0.15 Vvsthe reversible hydrogen electrode and a Tafel slope of 51 mV/decade. In addition, remarkable stability with no current decay for over 20,000 s of testing was observed. The perpendicularly oriented nanostructure of the electrocatalyst on a highly carbon-porous electrode favored more exposedactive sites. Such, an open 3D structure leads to an easily diffused electrolyte in which the exposed active edges of MoSe2nanostructures are a key issue to fully realizing the excellent electrochemical properties.

Controlling the electrochemical hydrogen generation and storage in graphene oxide by in-situ Raman spectroscopy

Hydrogen, generated from water splitting, is postulated as one of the most promising alternatives to fossil fuels. In this context, direct hydrogen generation by electrolysis and fixation to graphene oxide in an aqueous suspension could overcome storage and distribution problems of gaseous hydrogen. This study presents time-resolved determination of the electrochemical hydrogenation of GO by in-situ Raman spectroscopy, simultaneous to original functional groups elimination. Hydrogenation is found favoured by dynamic modulation of the electrochemical environment compared to fixed applied potentials, with a 160% increase of C–H bond formation. Epoxide groups suppression and generated hydroxide groups point at these epoxide groups being one of the key sites where hydrogenation was possible. FTIR revealed characteristic symmetric and asymmetric stretching vibrations of C–H bonds in CH 2 and CH 3 groups. This shows that hydrogenation is significantly also occurring in defective sites and edges of the graphene basal plane, rather than H-Csp 3 groups as graphane. We also determined a −0.05 V RHE reduction starting potential in alkaline electrolytes and a 150 mV cathodic delay in acid electrolytes. The identified key parameters role, together with observed diverse C-H x groups formation, points at future research directions for large-scale hydrogen storage in graphene.

Metal-organic framework derived ellipse-like NiS2 nanocatalyst for stable electrochemical hydrogen generation in alkaline electrolyte

The development of non-precious and high-efficient electrocatalysts to enhance the activity and stability in alkaline media is impending for massive hydrogen and oxygen production. In this study, NiS2 nanoparticles array with ellipse-like topography was fabricated via simple hydrothermal and sulfurization treatment. The NiS2-400 featured with the unique loose stacking topographic architecture contributes to more exposed active sites, the smaller contact resistance between electrode/electrolyte, faster ion diffusion and electron transfer. As a result, NiS2-400 electrode requires only overpotentials of 116 and 178 mV to drive current densities of 10 and 50 mA cm−2 in 1.0 M KOH towards the hydrogen evolution reaction (HER), coupled with a Tafel slope of 93.0 mV dec−1. Moreover, the resultant NiS2-400 nanoparticles exhibit excellent electrochemical stability for more than 50 h. In addition, the density functional theory (DFT) calculation further confirms that the (200) facet acts as the predominant active site, contributing to the enhanced HER performance.

Production of Hydrogen in High-Temperature Molten Salts, and Its Utilization for the Clean Preparation of Metals and Alloys

The economical production of hydrogen is an essential step towards the decarbonization of industrial sectors, including metals and alloys production processes. The available water electrolysis technologies used for hydrogen generation suffer from limitations, including the high voltage required in the electrolysis unit (typically > 1.8 V), reducing the energy efficiency of such processes and their compatibility with solar power systems. Here, the electrochemical generation of hydrogen in high-temperature molten salts at voltages as low as 1 V is discussed. Moreover, the utilization of the electrogenerated hydrogen for the in situ reduction of metal oxides into corresponding metals are evaluated using techniques such as voltammetry and constant voltage electrolysis operations combined with X-ray diffraction and electron microscopy examinations. To this end, the hydrogen generation in molten LiCl under humid atmosphere, and the hydrogen reduction of oxides of iron, nickel and cobalt in molten salt at the low-cell voltage of around 1.5 V are studied, and compared with each other. Moreover, the intermediates compounds formed during the reduction processes are identified, shedding light onto mechanisms involved in low-voltage green production of metals in molten salts.

Ni2 Se3 -CuSex Heterostructure as a Highly Efficient Bifunctional Electrocatalyst for Urea-Assisted Hydrogen Generation.

Coupling urea oxidation reaction (UOR) with hydrogen evolution reaction (HER) is an attractive alternative anode reaction for electrochemical hydrogen generation with low energy consumption. However, the development of highly efficient bifunctional electrocatalysts is still a challenge. In this work, Ni2 Se3 -CuSex heterostructure was synthesized on copper foam (Ni3 Se2 @CuSex /CF) by electrodeposition accompanied by a selenization process. Benefiting from the abundant active sites, faster reaction kinetics, and modulated electronic structure, the self-supporting Ni3 Se2 @CuSex /CF electrode exhibited superior catalytic performance. Extremely low overpotentials of 120 and 140 mV were achieved at the current density of 100 mA cm-2 for HER/UOR, respectively. Respectively, in HER||UOR coupled electrolyzer for H2 generation, the Ni3 Se2 @CuSex /CF||Ni3 Se2 @CuSex /CF delivered a low cell voltage of 1.49 V to reach a high current density of 100 mA cm-2 along with good stability, outperforming most of the other well-developed materials to date. The rational design of coupled heterostructure as bifunctional electrodes is a promising approach for energy-saving H2 production.

Synthesis of Self-Supported Cu/Cu3P Nanoarrays as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

Owing to the energy crisis and environmental pollution, it is essential to develop cheap, environmentally friendly and sustainable energy to replace noble metal electrocatalysts for use in the hydrogen evolution reaction (HER). We report herein that a Cu/Cu3P nanoarray catalyst was directly grown on the surfaces of Cu nanosheets from its Cu/CuO nanoarray precursor by a low-temperature phosphidation process. In particular, the effects of phosphating distance, mass ratio and temperature on the morphology of Cu/Cu3P nanoarrays were studied in detail. This nanoarray, as an electrocatalyst, displays excellent catalytic performance and long-term stability in an acid solution for electrochemical hydrogen generation. Specifically, the Cu/Cu3P nanoarray-270 exhibits a low onset overpotential (96 mV) and a small Tafel slope (131 mV dec−1).