Electrode For Hydrogen Evolution Reaction Research Articles

Superior MoTiN and NiMoTiN coating electrode with platinum-like catalytic activity fabricated by plasma electrolytic oxidation

Electrolyzing water is an effective and feasible technology to achieve a large-scale hydrogen production in industry. However, it is still challenging to develop an efficient approach to fabricate a superior and stable hydrogen evolution reaction (HER) electrodes with low cost and outstanding catalytic efficiency. This work presents an innovative surface modification technique of plasma electrolytic oxidation (PEO) to fabricate superior MoN based coating electrodes. By simply introducing Na2MoO4 and NiAc2 into the electrolyte, a novel MoTiN and NiMoTiN coatings were successfully achieved on the surface of a titanium substrate by PEO and annealing treatments, which exhibits excellent mechanical adhesion and platinum-like catalytic properties. Importantly, it has been demonstrated that the newly formed MoTiN solid solution combined by active Mo2N and conductive TiN can contribute the superior catalytic activity and the subsequent Ni doping can effectively stabilize the structure and activity of MoTiN. Under the alkaline environment of 1 M KOH, the MoTiN and NiMoTiN coated electrodes require only 126 and 121 mV overpotential, respectively, to achieve a current density of 10 mA cm−2. Additionally, under the same test conditions, NiMoTiN can operate stably for over 24 h, demonstrating excellent HER catalytic activity and stability. This work provides new insights into the preparation of HER electrodes with superior mechanical properties and excellent catalytic performance towards industrial hydrogen production.

Stainless steel as gas evolving electrodes in water electrolysis: Boosting the electrocatalytic hydrogen evolution reaction on electrodeposited Ni@CoP modified stainless steel electrodes

High efficient and durable electrocatalytic electrodes play a vital role in energy conversion and storage. In this concern, water electrolysis technology needs high performance electrodes with high activity and stability to implement this technology for green hydrogen production. Here, this study reports on the development of self-supported electrodes for the hydrogen evolution reaction (HER) based on sequential electrodeposition technique. First, the CoP has been deposited on stainless steel mesh (SSM) electrode followed by deposition of Ni to form Ni@CoP electrocatalysts standing on SSM. The loading amount of Ni was studied to achieve a high catalytic activity. The developed electrodes have been investigated with FE-SEM, EDX, XRD and XPS to identify their morphological properties as well as their chemical states and compositions. Electrocatalytic activity and durability have been studied in alkaline media by different electrochemical methods, such as LSV, EIS and CP. The results showed that the optimum deposition time of 10 min (10Ni@CoP) exhibited the higher catalytic activity in term of overpotential and Tafel slope giving a overpotential of 188 mV at 10 mA cm−2 with a small Tafel slope of 69 mV.dec−1 compared to CoP electrode with overpotential 266 mV and Tafel slope of 105 mV.dec−1 highlighting the role of Ni in enhancing the catalytic activity of the developed electrodes towards HER. Moreover, the Ni@CoP showed high stability under continues electrolysis at 50 and 100 mA.cm−2. These findings have been discussed in light of porous structure of the electrodes and introducing of Ni particles which led to creating more active sites and enhancing the hydrogen adsorption/desorption and thus facilitating the HER kinetics. The facial preparation method of self-supported electrodes and the obtained activity and stability of Ni@CoP electrodes render them as potent electrodes for HER in alkaline water electrolysis.

Conversion of Layered WS2 Crystals into Mixed-Domain Electrochemical Catalysts by Plasma-Assisted Surface Reconstruction.

Electrocatalytic water splitting is crucial to generate clean hydrogen fuel, but implementation at an industrial scale remains limited due to dependence on expensive platinum (Pt)-based electrocatalysts. Here, an all-dry process to transform electrochemically inert bulk WS2 into a multidomain electrochemical catalyst that enables scalable and cost-effective implementation of the hydrogen evolution reaction (HER) in water electrolysis is reported. Direct dry transfer of WS2 flakes to a gold thin film deposited on a silicon substrate provides a general platform to produce the working electrodes for HER with tunable charge transfer resistance. By treating the mechanically exfoliated WS2 with sequential Ar-O2 plasma, mixed domains of WS2, WO3, and tungsten oxysulfide form on the surfaces of the flakes, which gives rise to a superior HER with much greater long-term stability and steady-state activity compared to Pt. Using density functional theory, ultraefficient atomic sites formed on the constituent nanodomains are identified, and the quantification of atomic-scale reactivities and resulting HER activities fully support the experimental observations.

Highly active ultralow loading Pt electrodes for hydrogen evolution reaction developed by magnetron sputtering

Developing cost-effective components for PEM electrolyzers is key to transforming renewable energy into H2. Platinum is a scarce and expensive material but also, is the most active known catalyst for hydrogen evolution reaction in PEM electrolysis; thus it is of utmost importance to focus on developing electrocatalysts that utilize the minimum amount of platinum without losses in cell performance to make PEM electrolysis affordable. In addition, and with the aim of scaling up electrode production, it is imperative to develop a robust automated industrial manufacturing process to avoid the waste of catalyst during electrode preparation. In this work, magnetron sputtering gas aggregation method is studied for developing three low loading Pt electrodes (0.105, 0.062, and 0.052 mg cm−2), achieving remarkable overpotentials as low as 8 mV at 10 mA cm−2 for HER, showing similar activity than commercial Pt electrodes with more than 4 times less Pt (compared to 0.3 mgcm−2 Pt commercial GDL).

Molybdenum, tungsten doped cobalt phosphides as efficient catalysts for coproduction of hydrogen and formate by glycerol electrolysis

H2 and formate are important energy carriers in fuel-cells and feedstocks in chemical industry. The hydrogen evolution reaction (HER) coupling with electro-oxidative cleavage of thermodynamically favorable polyols is a promising way to coproduce H2 and formate via electrochemical means, highly active catalysts for HER and electrooxidative cleavage of polycols are the key to achieve such a goal. Herein, molybdenum (Mo), tungsten (W) doped cobalt phosphides (Co2P) deposited onto nickel foam (NF) substrate, denoted as Mo-Co2P/NF and W-Co2P/NF, respectively, were investigated as catalytic electrodes for HER and electrochemical glycerol oxidation reaction (GOR) to yield H2 and formate. The W-Co2P/NF electrode exhibited low overpotential (η) of 113 mV to attain a current density (J) of −100 mA cm−2 for HER, while the Mo-Co2P/NF electrode demonstrated high GOR efficiency for selective production of formate. In situ Raman and infrared spectroscopic characterizations revealed that the evolved CoO2 from Co2P is the genuine catalytic sites for GOR. The asymmetric electrolyzer based on W-Co2P/NF cathode and Mo-Co2P/NF anode delivered a J = 100 mA cm−2 at 1.8 V voltage for glycerol electrolysis, which led to 18.2 % reduced electricity consumption relative to water electrolysis. This work highlights the potential of heteroelement doped phosphide in catalytic performances for HER and GOR, and opens up new avenue to coproduce more widespread commodity chemicals via gentle and sustainable electrocatalytic means.

Assembly of amorphous CoP electrocatalysts on flexible polyester textile for alkaline hydrogen evolution reaction

The design of low-price and flexible hydrogen evolution reaction (HER) electrode has attracted much attention on efficient utilization of sustainable hydrogen energy. Herein, we reported a facile fabrication of flexible HER electrode by anchoring CoP electrocatalyst on polyester (PET) textiles. Conductive nickel cloth (NC-PET) substrate was firstly obtained by sequentially electroless plating and electroplating of metallic Ni on textile fibers. The amorphous CoP catalyst was then assembled on the NC-PET substrate by controlled electrodeposition to obtain flexible HER electrode (CoP-NC/PET). The flexible CoP-NC/PET showed a low overpotential of 63 mV at 10 mA cm−2 for HER, with a Tafel slope of 48.09 mV dec−1 in 1 M KOH solution. The faradaic efficiency of CoP-NC/PET measured at 100 mA cm−2 current density was estimated to be nearly 100%. No significant loss of HER catalytic activity was observed after 2000 cycles and 1000 times folding operations, demonstrating the high flexibility and stability of the present CoP-NC/PET electrode.

Insight into in situ grown Ru-based integrated electrodes for hydrogen evolution reaction: Boosted mass transfer efficiency and promoted intrinsic activity

The rational design of high-performance electrodes for hydrogen evolution reaction (HER) is crucial for water splitting in industrial applications. Herein, dual regulation of both mass transfer and intrinsic activity for in situ grown integrated electrodes was achieved via 3D electrode design and interfacial regulation. An innovative ruthenium (Ru)-based integrated electrode was constructed through a gravity-guided chemical vapor deposition (CVD) technique, featuring a three-dimensional carbon nanotube (CNT) network structure with embedded Ru clusters. This interlaced CNT structural configuration with high porosity and superhydrophilicity improved bubble transfer efficiency by reducing bubble coverage, bubble departure time, and bubble diameter at the reaction interface. Subsequently, the introduction of appropriate covalent Ru-O bonds on the interface of the integrated electrode boosted its intrinsic HER activity. Furthermore, DFT and AIMD calculations elucidated that the formation of covalent Ru-O bonds could reduce the adsorption and desorption of H*/OH* species, strengthen the hydrogen-bond network, and optimize the orientation of water molecules in the double electric layer (EDL). Consequently, the RuOCNT integrated electrode demonstrated a remarkably low overpotential of 41 mV at 10 mA cm−2 in a 1.0 M KOH solution and the high durability indicated by a degradation rate of only 140 μV h−1 at 100 mA cm−2 after 100 h. In addition, an in-depth analysis was carried out to distinguish the contribution of covalent Ru-O sites and electrode’s 3D structure to the boosted HER activity. This study highlighted a new approach to fabricating and understanding an efficient electrode by combining electrode engineering and active site modification to enhance HER efficiency in a mutually reinforcing manner.

Highly Efficient and Stable Overall Water Splitting Electrocatalyst α-Co(OH)2@PN/NF with Hierarchical and Mesoporous Structure

Exploiting efficient, stable, and cost-effective bifunctional water splitting catalysts is extremely challenging. Here, we developed three-dimensional hierarchical porous catalysts with heterogeneous interfaces, α-Co(OH)2@PN/NF, by a facile two-step electrodeposition approach. This bifunctional electrocatalyst exhibits excellent hydrogen and oxygen evolution performance as well as stability in alkaline aqueous environments. In 1 M KOH solution, small overpotential of 187 mV was needed to drive the hydrogen evolution reaction (HER) at 100 mA cm−2, while the overpotential for the oxygen evolution reaction (OER) was 324 mV at 100 mA cm−2 current density. In addition, the two-electrode electrolytic cell with α-Co(OH)2@PN/NF electrodes for HER and OER required only approximately 1.74 V at 100 mA cm−2 with over 75 h of stable operation. According to the physical-chemical characterization results and electrochemical tests, such excellent performance was attributed to the synergistic effect of the heterogeneous interface and the hierarchical porous structure between α-Co(OH)2 and the nickel oxide layer, as it facilitates the transfer of electrons and the diffusion of ions.

Ru nanoparticles immobilized on self-supporting porphyrinic MOF/nickel foam electrode for efficient overall water splitting

To achieve carbon neutrality, the development of effective and durable electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of utmost importance. Herein, the Ru3.4-PMOF/NF electrode was successfully prepared by immobilizing Ru nanoparticles on porphyrinic metal-organic framework/nickel foam (PMOF/NF), effectively driving both the OER and the HER in an alkaline electrolyte. To achieve 10 mA cm−2, the Ru3.4-PMOF/NF electrode only required overpotentials of 19 and 215 mV for HER and OER, respectively. For overall water splitting, an ultra-low cell voltage of 1.468 V was required to drive 10 mA cm−2, surpassing the performance of the integrated Pt/C and RuO2 couple electrode (1.6627 V). The outperformed electrocatalytic activity could be ascribed to the well-dispersed Ru nanoparticles, the self-reconstruction of PMOF, the synergistic effect, and the lamellar morphology. This study offers a promising approach for the development of ruthenium-doped electrodes that can enhance the efficiency of electrocatalytic water splitting.

A review of modulation strategies for improving the catalytic performance of transition metal sulfide self-supported electrodes for the hydrogen evolution reaction.

Electrocatalytic water splitting is considered to be one of the most promising technologies for large-scale sustained production of H2. Developing non-noble metal-based electrocatalytic materials with low cost, high activity and long life is the key to electrolysis of water. Transition metal sulfides (TMSs) with good electrical conductivity and a tunable electronic structure are potential candidates that are expected to replace noble metal electrocatalysts. In addition, self-supported electrodes have fast electron transfer and mass transport, resulting in enhanced kinetics and stability. In this paper, TMS self-supported electrocatalysts are taken as examples and their recent progress as hydrogen evolution reaction (HER) electrocatalysts is reviewed. The HER mechanism is first introduced. Then, based on optimizing the active sites, electrical conductivity, electronic structure and adsorption/dissociation energies of water and intermediates of the electrocatalysts, the article focuses on summarizing five modulation strategies to improve the activity and stability of TMS self-supported electrode electrocatalysts in recent years. Finally, the challenges and opportunities for the future development of TMS self-supported electrodes in the field of electrocatalytic water splitting are presented.

Effect of Electrochemical Surface Oxidation on Intrinsic Activity Towards the Hydrogen Evolution Reaction of Ultra-Smooth Nanocrystalline Ni Thin Films

Green hydrogen has emerged as a leading contender in the pursuit of a sustainable energy transition, driving the need for optimized catalysts in hydrogen production. Therefore, considerable effort is taken to replace the highly active, yet expensive Pt-group metals with non-noble alternatives such as Ni. Understanding the hydrogen evolution reaction (HER) mechanism on well-performing Ni surfaces is essential for gaining fundamental knowledge and implementing this in practical applications. While high surface area structures are typically designed for enhanced efficiency, there is limited research available on the fundamental aspects of thin films and smooth surfaces, which are crucial for benchmarking intrinsic catalytic activity and elucidating catalytic mechanisms. To address this gap, we perform a combined microstructural and electrochemical evaluation of smooth Ni thin film electrodes to analyze HER in alkaline media.This study aimed to evaluate the intrinsic catalytic properties of nanocrystalline Ni thin films and the effect of electrochemical oxidation on the catalytic behavior, while precisely monitoring the evolution of the film surface state and roughness. In addition to experimental work, Density Functional Theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations are used to understand HER on oxide-modified Ni surfaces and the role of different elementary processes involved in the HER mechanism.Nanocrystalline low-roughness Ni electrodes for HER were produced via magnetron sputter deposition to minimize the difference between geometrical and electrochemical surface area. This means we find intrinsic material properties directly, bypassing the need for additional measurements for real surface area determination. The analysis of catalyst activities towards HER as well as the oxidation process [1] was performed via cyclic voltammetry, using a three-electrode setup. Within the conducted studies, we can report a significant lowering of the overpotential for HER upon in-situ oxidation of the electrodes due to the existence of NiO, and Ni(OH)2 on the Ni catalyst surface [2], leading also to a limitation of the deactivation processes. Further analysis including topography evaluation (AFM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) in combination with selected area diffraction (SAED) of the as-deposited and oxidized electrodes confirmed that the observed effect can be assigned to the availability of oxides on the surface assuredly (Figure 1). Additionally, theoretical calculations and simulations (DFT, KMC) support the experimental data and derived theories.In conclusion, the beneficial effect of NiO and Ni(OH)2 presence on Ni surfaces was examined and successfully proven by a combination of electrochemical measurements, material characterization, theoretical calculations, and a careful experimental design that minimizes the influence of interfering factors, such as surface roughness.

Enhanced Hydrogen Evolution Reaction Performance in Alkaline Water Electrolysis: Tuning the 1T Structure of Ni Doped MoS2 Via Co-Sputtering System

Molybdenum disulfide (MoS2) is a promising catalyst for the hydrogen evolution reaction (HER) in alkaline media due to its low cost and abundance. However, its HER activity is not sufficient for practical application because of its electrochemically inert basal plane and suboptimal hydrogen adsorption energy for HER. Herein, we present a facile synthesis approach to fabricate MoS2/Ni HER electrode with 1T structure using co-sputtering of both MoS2 and Ni. Our results indicated that Ni doping plays a critical role in introducing 1T phase in MoS2 structure, leading to an active basal plan, optimized hydrogen adsorption energy, and strong adhesion between the catalyst film and Ni substrate for highly efficient HER performance and durability. We confirmed that the 1T-phase yield, morphologies, and HER activity are affected by sputtering parameters. Our optimized MoS2/Ni electrode exhibited an overpotential of ~91 mV at 10 mAcm-2 and no significant change in HER performance after 1000 cycles operation in 1 m KOH. Single cell test including our optimized electrode exhibited enhanced overpotential and durability compared to a reference cell, highlighting the potential for commercialization in alkaline water electrolysis industry.

(Invited) Tuning the Activity of Iron Phosphide Electrocatalysts for Sustainable Energy Conversion

Electrocatalysis is a promising approach for the sustainable conversion of renewable energy sources, such as solar and wind power, into chemical energy that can be stored and used on demand. By harnessing renewable electricity to drive electrochemical reactions, we can produce fuels and chemicals in a way that is both clean and cost-effective. As we continue to develop new electrocatalytic materials and improve the efficiency of existing processes, the potential for electrocatalysis to transform our energy system will only continue to grow.We report the use of iron phosphide (Fe2P, FeP) in several electrocatalytic applications, such as reduction of nitrate ions (NO3), hydrogen and oxygen evolution studies. The electrochemical reduction of the nitrate ion (NO3), a widespread water pollutant, to valuable ammonia (NH3) is a promising approach to achieving green energy conservation. Particularly, FeP and Fe2P phases were successfully demonstrated as efficient catalysts for NH3 generation. Detection of the in-situ formed product using a bi-potentiostat was achieved by electrooxidation of NH3 to nitrogen (N2) on a Pt electrode. The Fe2P catalyst exhibits the highest Faradaic efficiency (96%) for NH3 generation with a yield (0.25 mmol h−1 cm-−2 or 2.10 mg h−1 cm−2) at −0.55 V vs. reversible hydrogen electrode (RHE). To get relevant information about the reaction mechanisms and the fundamental origins behind the better performance of Fe2P, density functional theory (DFT) calculations were performed.In addition to NH3 synthesis, the iron phosphide catalyst was used in electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) studies. To enhance the catalytic activities of the obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures. Heat-treatment at 500°C under a reductive atmosphere induced structural changes in the samples: (i) Fe2P yielded a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities of heat-treated Fe3P−500°C, and Fe2P/FeP−500°C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M H2SO4. The lowest HER electrode potential of 110 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2 was achieved with a Fe2P/FeP−500°C catalyst. The intrinsic activity of FeP catalysts was also tuned and studied for OER.

Controllable synthesis and super electrochemical stability of copper phosphide (Cu3P) nanosheets catalyst in nearly neutral electrolyte

The catalytic activity and stability of cost-effective and highly efficient bifunctional electrocatalysts are crucial for electrochemical water splitting. However, the use of strongly alkaline or acidic electrolytes, which are commonly employed, poses environmental concerns. Therefore, the development of efficient electrocatalysts that can operate stably in neutral or near-neutral electrolytes holds significant importance. In this study, a self-supporting Cu3P/NF electrode was fabricated using a two-step method, wherein metal phosphide Cu3P was grown on a nickel foam (NF) substrate. Notably, the Cu3P/NF electrode exhibits an unexpected enhancement in electrochemical activity and stability when operated in an electrolyte consisting of CuSO4 and Na2CO3. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on the Cu3P/NF electrode require overpotentials of 131 mV and 230 mV, respectively, to achieve a current density of 10 mA cm−2 and 50 mA cm−2. Moreover, the stability of the Cu3P/NF electrode for HER and OER is improved by 90.22 % and 74.54 %, respectively, with the inclusion of CuSO4 in the Na2CO3 electrolyte. The improved catalytic performance and stability of Cu3P/NF electrode with the addition of CuSO4 can be attributed to the prevention of Cu + oxidation through Cu2+ and the formation of a local H+ adsorption electric field by the SO42− electron cloud. These factors contribute to the enhanced electrocatalytic activity and stability of Cu3P. This work expands the efficient utilization of electrocatalysts in near-neutral electrolytes, which is of great value for the widespread application of electrocatalysts and environmental protection.

Multinary intermetallic with enhanced catalytic activity and prolonged stability at high current density for electrochemical hydrogen production

Developing robust and efficient nonprecious metal-based electrocatalysts toward hydrogen evolution reaction (HER) is a big challenge for green and sustainable energy since insufficient catalytic activity and poor stability of current catalysts cannot meet the application requirements. This work reports a freestanding HER electrode FeNiCuAlMo prepared by arc-melting and chemical dealloying methods. The HER performance firstly improves and then declines with the increase of dealloying time. When the dealloying time is 3 h, the electrode shows optimal catalytic performance. The fabricated electrode is composed of AlMo3 and Al5CuMo2, where micro-sized AlMo3 particles are embedded in cellular dendritic Al5CuMo2. Impressively, it displays excellent HER performance, including a small overpotential of 173 mV at a current density of 500 mA/cm2 and outstanding long-term stability for 100 h of continuous hydrogen evolution at 1000 mA/cm2 in an alkaline electrolyte without obvious attenuation. The intrinsic activity of the electrodes combined intermetallic compounds with hierarchical porous structure provides several effects, including enhanced massive active sites, electrolyte access, electron transport, and fast gas release that contribute jointly to enhancing HER activities. The micro-sized AlMo3 particles provide robust framework for the dendritic Al5CuMo2 active sites center, allowing the exposure of enough active sites and simultaneously maintaining good stability. The highly stable and active electrocatalytic HER property makes it as a promising candidate for practical hydrogen production.

Fabrication of Gold Nanoparticles Embedded Laser-Induced Graphene (LIG) Electrode for Hydrogen Evolution Reaction

The advancement of renewable energy technologies like water electrolysis and hydrogen fuel cells relies on the fabrication of effective and reliable catalysts for the hydrogen evolution process (HER). In this regard, we report gold nanoparticles embedded in laser-induced graphene electrodes for regulation of overpotential and electrocatalytic performance of hydrogen evolution reaction. Gold nanoparticles were deposited onto the LIG surface using electrode deposition via cyclic voltammetry (CV) at different cycle lengths. The catalyst fabrication technique enables the manipulation of many electrochemical parameters, such as overpotential value, charge transfer resistance, electrochemical active surface area, and tafel slope, through the adjustment of cyclic voltammetry (CV) cycles. The LIG-Au@50 sample demonstrates remarkable electrocatalytic characteristics, as evidenced by its low overpotential of 141 mV at a current density of 10 mA/cm2 and reduced tafel slope of 131 mV/decade in an acidic environment. Furthermore, the presence of an augmented electrochemical active surface area, a mass activity of 8.80 A/g, and a high turnover frequency of 0.0091 s−1 suggest elevated and significant accessibility to plentiful active sites. A significant decrease in charge transfer resistance resulted in an enhanced rate of the water-splitting reaction.

Mo2C-Based Ceramic Electrode with High Stability and Catalytic Activity for Hydrogen Evolution Reaction at High Current Density.

Developing robust electrodes with high catalytic performance is a key step for expanding practical HER (hydrogen evolution reaction) applications. This paper reports on novel porous Mo2C-based ceramics with oriented finger-like holes directly used as self-supported HER electrodes. Due to the suitable MoO3 sintering additive, high-strength (55 ± 6MPa) ceramic substrates and a highly active catalytic layer are produced in one step. The in situ reaction between MoO3 and Mo2C enabled the introduction of O in the Mo2C crystal lattice and the formation of Mo2C(O)/MoO2 heterostructures. The optimal Mo2C-based electrode displayed an overpotential of 333 and 212mV at 70°C under a high current intensity of 1500 mAcm-2 in 0.5m H2SO4 and 1.0m KOH, respectively, which are markedly better than the performance of Pt wire electrode; furthermore, its price is three orders of magnitude lower than Pt. The chronopotentiometric curves recorded in the 50 - 1500 mAcm-2 range, confirmed its excellent long-term stability in acidic and alkaline media for more than 260h. Density functional theory (DFT) calculations showed that the Mo2C(O)/MoO2 heterostructures has an optimum electronic structure with appropriate *H adsorption-free energy in an acidic medium and minimum water dissociation energy barrier in an alkaline medium.

Growth of few-layer flower-like MoS2 on heteroatom-doped activated carbon as a hydrogen evolution reaction electrode

MoS2 is an attractive cost-effective replacement for Pt-catalysts in HER applications, but its usefulness is constrained by weak electrical conductivity and activity density. Herein, a low-cost highly activated carbon/molybdenum disulfide (AC/MoS2) electrocatalyst has been developed through surfactant-assisted hydrothermal synthesis of MoS2 nanosheets on the heteroatom-doped AC derived from green biomass source. The high surface area conductive carbon matrix was prepared through green activation of wasted petal rose flower. To provide the many active edge sites, F108 polymer was utilized to control of the well-distribution of flower-like few-layer MoS2 nanosheets on the nanoporous conductive carbon matrix. The prepared composite demonstrated a low overpotential of 136 mV in 10 mA cm−2 with Tafel slope of 72 mV dec−1 in 0.5 M H2SO4. Notably, the AC/MoS2 construction displayed significantly lower overpotential than commercial Pt/C catalyst at the current densities higher than 410 mA cm−2.

Preparation and characterization of groove-shaped Ti/Cu layered electrode with superior hydrogen evolution performance

In this study, a comprehensive investigation on the performance of laminated electrodes for hydrogen evolution reaction (HER) is conducted using experiments and numerical simulation. A laminated composite electrode with superior catalytic activity is designed, synthesized and tested, which is comparably researched with traditional homogeneous electrodes. A Ti/Cu laminated electrode with a slot width of 250 µm is fabricated by explosive welding and an electrochemical corrosion process is applied to create groove-shaped interface. The results show that the grooved laminated electrode has superior hydrogen precipitation performance and conductivity, exceptional stability, and minimal potential fluctuation. Hydrogen production efficiency of laminated electrode is 120% higher than that of Cu electrode, which is verified in our self-made hydrogen-making device. COMSOL simulation results were found to be consistent with the experimental findings. Overall, this study provides valuable insight into enhancing electrode performance, with broad engineering implications.

Polyolefin-derived substrate-grown carbon nanotubes as binder-free electrode for hydrogen evolution in alkaline media

Switching from a linear mode of waste management to a circular loop by transforming plastic waste into carbon nanotubes (CNTs) is a promising approach to current plastic waste treatment. One of the many applications of CNTs is its use for electrocatalytic water splitting for hydrogen evolution. Existing methods of CNTs-based hydrogen evolution reaction (HER) electrode fabrication involve additives like polymeric binders and additional steps to improve CNT dispersion, which are detrimental to the CNT structure and properties. The in-situ fabrication approach can potentially be a one-pot solution to HER electrode synthesis. In this study, polyolefins pyrolysis gas and a Co:Ni:Mg catalyst were used to fabricate binder-free CNTs-based electrodes on different substrates for HER. The study assessed CNT quality on conductive carbon paper, semiconductive silicon, and dielectric glass substrates, evaluating their HER performance in 1 M KOH. A mixture of hollow-core, bamboo-like, and cup-stacked arrangement nanotubes were synthesized on the substrates, with CNTs on glass and carbon paper substrates possessing better graphitization than CNTs grown on silicon. This is in agreement with HER performance, whereby the as-prepared electrodes required overpotentials of 267 mV, 241 mV, and 216 mV for silicon, glass, and carbon paper, respectively, to achieve 10 mA/cm2. Despite being poorly conductive, the glass substrate electrode achieved a lower overpotential than the silicon electrode. Additionally, the as-prepared silicon electrode faced a delamination issue likely attributed to the lower surface energy of the silicon substrate surface, demonstrating the weaker adhesion between the CNTs and silicon surface. The proposed approach thus showed that the in-situ fabricated electrodes performed better than separately synthesized CNTs prepared into electrodes by 27.4% and 14.2% for carbon paper and glass substrates, respectively. The improved performance of the as-prepared, binder-free electrodes can be linked to the lower charge-transfer resistance and reduced contact resistance between the CNTs and substrate.