Hydrogen Evolution Process Research Articles

Unleashing solar energy's full potential: Synergetic thermo-photo catalysis for enhanced hydrogen production with metal-free carbon nitrides

Conventional photocatalytic hydrogen production processes are limited by their dependency on photons possessing energy levels surpassing the material's bandgap, thus restricting their ability to utilize the full solar spectrum. Conversely, in thermal catalysis, although the entire solar spectrum is accessible, high-energy photons remain underutilized, and reaction temperatures are often elevated. To address these issues, thermo-photo catalysis is proposed to effectively harness the full spectrum of solar energy under gentle conditions. In this study, a narrow-bandgap carbon nitride catalyst with a bandgap of 2.3 eV was synthesized for the specific purpose of hydrogen production from water through thermo-photo catalysis. Results revealed that under thermo-photo catalytic (TPC) conditions, impressive hydrogen generation rates of 3009.6 μmol·g−1·h−1 and 7090.7 μmol·g−1·h−1 were achieved without and with the application of an external heat source, respectively. Both of them substantially surpassed the cumulative hydrogen production rates achieved via photocatalytic (PC) and thermocatalytic (TC) pathways, demonstrating a remarkable synergy between photonic and thermal energies in the hydrogen evolution process. The synergetic factor with an external heat source applied (2.29) was lower than that without an external heat source (3.02), indicating that there is a better synergy between the photo energy and the thermal energy provided by photothermal conversion than the thermal energy supplied by external heat sources. The properties of photo-generated carriers under various temperature regimes were further examined by photoelectrochemically tests, and electron paramagnetic resonance experiments elucidated the pivotal influence of both photo and thermal energy on radical species, offering a microscopic understanding of the mechanism responsible for the enhanced hydrogen production rate in thermo-photo catalysis.

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.

Collaborative coupling catalytic interface enabling efficient hydrogen evolution in universal-pH electrolytes and seawater

Developing particularly effective and synergistic non-noble metal electrocatalysts for complex chemical processes remains an enormous challenge. Herein, the collaborative catalytic interface among rare earth compounds, bimetallic carbide, and N-doped carbon is demonstrated to accelerate the hydrogen evolution process in acid-base electrolytes and seawater. Therefore, the HER performance of the resultant electrocatalyst in both 1.0 M KOH and 0.5 M H2SO4 with the overpotentials of 70 and 79 mV, to achieve the current density of 10 mA cm−2. In addition, they also show excellent performance of HER in natural seawater and have good characteristics in catalytic activity and stability, which is reflected in the slight decrease of activity after the 5000 cyclic voltammetry (CV) cycle and almost no attenuation after electrolysis for 10 h. This work will pave a new way for collaborative coupling interface catalysis strategy to boost electrocatalytic hydrogen production in acidic, alkaline, and seawater.

Solvent-assisted phase modification of Ni[sbnd]P material to boost electrocatalytic water splitting and charge storage capacity

Due to their redox features, Fe/Ni-phosphides and phosphates could be utilized as multi-functional electrode materials for hydrogen and oxygen evolution processes (HER and OER) and supercapacitors, however, regulation in their geometry and electrical structure for further performance improvement is still challenging. Herein, we developed a solvent-assisted approach to modify the NiP material's phase, growing Ni2P, Ni12P5, and Ni(PO3)2 cross-linked nanosheets on Ni-foam using the same precursor and different solvents. When compared to Ni2P and Ni12P5, the Ni(PO3)2 sample showed outstanding activity and endurance towards HER (134 mV overpotential@10 mA/cm2 and 112 mV/dec Tafel value) and OER (342 mV overpotential@10 mA/cm2 and 78 mV/dec Tafel value), respectively. Moreover, the specific capacitance of the Ni(PO3)2 electrode was found to be 4366 (at 10 mV/s) and 7582 mF/cm2 (at 1 mA/cm2). Theoretical calculations showed that the density of states and its distribution across the Fermi level increased in the order of Ni2P < Ni12P5 < Ni(PO3)2 which improved their conductivity and electronic properties, benefiting electrocatalytic HER and OER activity and the charge-storing capacity of Ni(PO3)2.

In situ study the effects of bias and electric field intensity on electrochemical migration behavior of Sn96.5Ag3.0Cu0.5 solder alloy

In this work, the influence of bias and electric field intensity on the electrochemical migration of SAC305 solder alloy is investigated using a self-designed in-situ thin electrolyte film device. The results indicate that when the bias is 0.5 V, a compact passivation film forms on the sample surface, effectively inhibiting dendrite growth. When the applied bias reaches 0.75 V, it is observed that specific corrosion products are generated between the two plates, and the occurrence of dendritic growth phenomena is still absent. Dendrite development is observed when a bias voltage of 1 V is applied. Regarding the electrode reactions, when the applied bias falls below 1.5 V, a notable polarization resistance is encountered in the anode reaction. In this case, the cathode reaction primarily entails the process of oxygen reduction. As the applied voltage climbs to 1.5 V, the anodic potential shows an increase, leading to a reduction in the polarization resistance of the anodic process that determines the rate of the electrochemical reaction. At this time, the cathode potential exhibits a comparatively negative value, leading to the progressive occurrence of the hydrogen evolution process. Additionally, the influence mechanism of bias on ECM is also proposed.

High-Performance and Stability Electrochromic Devices with a Water Isotopologue.

In this report, an ammonium metatungstate (AMT) and ferrous chloride [Fe(II)Cl2] electrochromic liquid (ECL) was synthesized using a hydrothermal method, with D2O used as the solvent instead of H2O. The results show that the use of D2O can improve the stability and performance of ECLs. The hydrogen evolution process in electrochromic devices (ECDs) filled with ECL becomes more difficult, while the material exchange process becomes easier. The ECD exhibits a color modulation amplitude of 58%@680 nm at 2 V. After 500 cycles, the device's performance remains above 95% at a current density of 1.5 mA/cm2. Hydrogen bonds in D2O solutions are expected to exhibit stronger forces compared to those in regular H2O solutions. Therefore, we hypothesize that enhancing the strength of hydrogen bonds in H2O solutions is an effective approach for improving the performance and stability of electrochromic solutions.

Modulating P-S anions of graphene supported amorphous nickel-iron nanocomposites by plasma to optimize overall water splitting activity

Hydrogen production by electrolysis of water is a key technology that has the potential to aid in the transition towards green sources of energy. In this regard, graphene-supported bifunctional electrocatalysts have shown to promote both oxygen evolution and hydrogen evolution processes. Although they are considered as one of the most potential electrocatalysts, modulation of their morphological structures and electronic configurations is challenging. Here, an efficient bifunctional electrocatalyst of graphene-supported NiFe-LDH with phosphorus-sulfur anion coordination is prepared based on the RF plasma treatment strategy. Reasonable P and S anion ratios optimize the partial coordination environment and crystal state, and effectively regulate the adsorption of OH∗, OOH∗, and protons, which consequently enhance the OER/HER performance. Plasma treatment generates vacancy defect structures for the catalyst, which modulates the surface morphology and electronic structure. Optimized graphene-supported NiFe-LDH catalysts with phosphorus-sulfur anion modulation show excellent electrocatalytic performance with 228 mV overpotentials for OER at 100 mA cm−2, in alkaline environments with excellent stability. This study offers recommendations for designing catalysts to produce effective water splitting.

The effects of polymorphism and lithium intercalation on the hydrogen evolution reaction for the basal planes of MoS2.

The activity of Li-intercalated MoS2 phases for the hydrogen evolution reaction is investigated using density functional theory. The most stable semiconducting 2H phase, the metallic 1T' phase, and a polymorphous surface composed of alternating H and T' phases (1T″) are investigated. The local structure of the MoS2 surface is found to define its reactivity. In all cases, active sites for the hydrogen evolution process are restricted to T-like sulphur sites. Li-intercalation is found to promote hydrogen evolution reaction reactivity for the H phase whilst having little effect on the T phase. While improved compared to the non-intercalated phase, the Li-intercalated H phase MoS2 still has minimal activity for the hydrogen evolution reaction. The same effect of intercalation is also found for another transition metal dichalcogenide, MoSe2. The ability to improve reactivity in this way makes ion intercalation a promising space for designing new 2D catalysts for the hydrogen evolution reaction.

Nickel and/or platinum modified crystalline silicon–carbon composites and their electrochemical behaviour towards the hydrogen evolution reaction

Generation of hydrogen is very important, as it is one of the most desired alternatives to fossil fuels. Moreover, designing of cheap and stable electrocatalysts is the task for the efficient generation of hydrogen with reasonable activity. Materials hybridization can be considered a tool for engineering different material properties. Composites of modified silicon such as C–Si, Ni/(C–Si), Pt/(C–Si), and Pt–Ni/(C–Si) were prepared (in weight percent) and studied as electrocatalysts for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 solution. The surface morphologies and chemical compositions of the composites were confirmed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), elemental mapping, and BET surface analysis. The electrochemical measurements of linear sweep voltammetry (LSV), Tafel plots, chronoamperometry, and electrochemical impedance spectroscopy (EIS) were used to study the behaviour of the prepared electrodes toward the hydrogen evolution process. Among the various prepared composites, [7%Pt–3%Ni]/[C–Si (1:1)] composite shows the best catalytic activity with the highest HER rate (940.95 µA cm−2 s−1), the lowest overpotential [0.358 V vs. (Ag/AgCl) ≈ 0.161 V vs. (RHE)] at 10 mA cm−2, and the lowest charge transfer resistance (2.657 Ω) compared to other prepared electrodes. In addition, it gives the highest values of 4.219 × 10−3 s−1 turn over frequency (TOF) and 642 mA g−1 mass activity. It shows good stability towards the hydrogen evolution reaction as the current density reaches about 34.28 mA cm−2 after 5 h.Graphical abstract

Al-doping-induced electronic structure modulation of CoSe2 for efficient hydrogen evolution reaction

The development of highly efficient, long-lasting, and earth-rich electrocatalysts for hydrogen evolution processes (HER) is crucial to the advancement of hydrogen energy. Due to its improved catalytic activity, extraordinary chemical stability, and low cost, pyrite cobalt selenide (CoSe2) has become an incredibly potential replacement for Pt-based HER electrocatalysts. However, because of limited hydrogen adsorption and accompanying restrictions in its electronic structure, its practical application has run into difficulties. Herein, we have introduced aluminum (Al) into CoSe2/CC nanowire arrays on carbon cloth using a simple hydrothermal and selenization method. The synthesized materials serve as highly effective catalysts for HER, with the optimized Al-CoSe2/CC demonstrating a significantly overpotential reduced by nearly 90 mV compared to pure CoSe2/CC (from 243 mV to 153 mV) at a current density at 10 mA cm−2 and a small Tafel slope of 88 mV dec−1. Moreover, these catalysts exhibit exceptional durability, sustaining their performance for 24 h. Based on the experimental results and subsequent density functional theory (DFT) calculations, it has been demonstrated that Al doping can significantly enhance the electronic conductivity, maximize the hydrogen evolution adsorption energy, and improve the charge transfer ability. This work offers a profound insight into the correlation between cation substitution in non-precious metal-based catalysts and the enhancement of intrinsic HER catalytic performance.

Effect of Surface Acidity of Codoped C,S-TiO2 on Their Photocatalytic Properties in the Hydrogen Evolution and Ethanol Oxidation Processes

Effect of Surface Acidity of Codoped C,S-TiO2 on Their Photocatalytic Properties in the Hydrogen Evolution and Ethanol Oxidation Processes

The electronic properties, stability and catalytic activity of metallofullerene (M@C60) for robust hydrogen evolution reaction: DFT insights

The development of low-cost, and highly active catalysts for electrocatalytic hydrogen evolution process is of great interest. Exohedral first row transition metal doped fullerenes based single atom catalysts (SACs) are expected to replace precious metal catalysts for sustainable and large-scale commercial scalability of hydrogen generation. Herein, a series of ten metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu & Zn) single atoms doped C60 fullerenes (metallofullerenes) are screened for hydrogen evolution reaction. All the studied metallofullerenes are optimized with the various possible spin states and the most stable spin states among them are selected for further analysis. The stability of electrocatalysts is evaluated via interaction energy analysis, which reveals that all the designed metallofullerenes are thermodynamically stable (−0.24 to −4.30 eV). The hydrogen adsorption (Eads) and Gibbs free energy results reveal that Fe@C60 complex has the best catalytic activity for hydrogen evolution process with optimal ΔGH value of 0.08 eV. FMO analysis declares appreciable variations in electronic properties of C60 fullerene upon doping. Moreover, density of states (DOS) analysis also corroborates with FMO analysis for designed metallofullerene (M@C60) catalysts and HM@C60 complexes. Exchange current density is plotted as a function free energy (ΔGH) for hydrogen evolution process over designed metallofullerene. The volcano plot reveals the near thermoneutral behavior of Fe@C60 catalyst for hydrogen evolution reaction. Overall, results presented here for systematic screening of potential HER from metallofullerene based single atom catalysis can remarkably contribute to the design and fabrication of electrocatalysts.

Carbonized polymer dots modified ZnIn2S4 microspheres for visible-light-driven hydrogen evolution promotion performance

To effectively separate electron-hole pairs produced by light, a heterojunction arrangement can be employed, thereby improving photocatalytic efficiency. In this study, a simple hydrothermal process is used to manufacture carbonized polymer dots/ZnIn2S4 (CPDs/ZIS) heterostructure, which enhances the light absorption and charge carrier lifetime in comparison to bare ZnIn2S4 (ZIS). Upon irradiation with visible light, the 3-CPDs/ZIS composite generates hydrogen at a rate of 133 μmol g−1 h−1, which is 8.9 times faster than that of pure ZIS. The addition of CPDs can increase the range of light that can be absorbed, extend the service life of the optical charge, increase the specific surface area, and promote charge separation and transmission, which could effectively accelerate the photocatalytic reduction reaction. The presence of CPDs results in the introduction of multiple transition energy states and a decrease in the H* adsorption free energy, which enhances the hydrogen evolution activity according to the theoretical calculation findings of density functional theory (DFT) and Gibbs free energy of the hydrogen evolution process. Combining theoretical calculations and experimental results, a direct Z-type heterojunction mechanism is proposed for the hydrogen evolution promotion effectiveness of CPDs/ZIS under visible light.

Cr(III)-complex tethered lacunary polyoxometalate as an efficient electrocatalyst for hydrogen evolution reaction in aqueous media

A lacunary polyoxometalate-based hybrid material, wherein Cr (acac)3 complex is covalently tethered through aminopropyltrimethoxysilyl groups to a Keggin-type lacunary phosphomolybdate anion, [PMo11O39]7-, is reported as a new heterogeneous electrocatalyst for the efficient electrocatalytic hydrogen evolution process. Physicochemical characterization techniques, like FT-IR spectroscopy, X-ray diffraction (XRD), and energy dispersive X-ray (EDX) analyses confirmed the successful functionalization and synthesis of desired material. The prepared hybrid material revealed eminent hydrogen evolution activity with a low overpotential of 330 mV to attain a 10 mA cm−2 current density and a Tafel slope of 150 mV.dec−1. Additionally, it also exhibited outstanding electrochemical stability in H2SO4 (0.5 M) over 8 h and catalytic activity retention even after 2000 catalytic cycles. This work introduces an appropriate procedure for preparing inexpensive and highly active electrocatalysts for replacing precious Pt counterparts in hydrogen evolution process.

Conducting polymer encrusted Cu/Mn-MOF-CNDs: A facile synthesis, characterization and its hydrogen evolution activity in alkaline media and seawater

The Composites of polyaniline-bimetallic metal-organic framework with carbon nanodots (PANI/bi-MOF@CNDs) were fabricated by chemically oxidising aniline monomer for the hydrogen evolution process (HER). In this investigation, the composite structure, topography, and characteristics were analysed. The Fourier transform infrared spectroscopy analyses found evidence of electrostatic interaction between the CNDs@MOF and the backbone of the PANI matrix. Investigations using scanning electron microscopy and transmission electron microscopy showed that the CNDs@MOF exhibited uneven crystals with an additional enveloping PANI material. In an alkaline medium, the produced PANI composite (PANI/bi-MOF@CNDs) electrocatalyst showed a small overpotential and significant Tafel slope (110 mV and 180 mV/dec at 10 mA/cm2), as well as the RCT value of about 12.26 Ω, determined from Nyquist plot. PANI composite structural characteristics and electrical conductivity have also resulted in a faster rate of electron charge transfer and more accessible surface edge active sites. In addition, the catalyst is stable for 48 h at the specified operating conditions, and no further buffered electrolytes are required. As a result of the enhanced electrochemical performance, a strategic approach for the development of low-priced electrocatalysts for power conversion has been discovered.

Synchronous construction of Ni2P/Cu3P in-situ loading and P doping for g-C3N4: Enhanced photocatalytic H2 evolution activity and mechanism

Research on the subject of photolysis focuses on the creation of effective non-precious metal co-catalysts. Graphitic carbon nitride (g-C3N4) is a promising candidate for photocatalytic hydrogen generation from water. But its photocatalytic activity is limited by the slow redox reaction, high carrier recombination rate, and inadequate optical absorption. Incorporating in situ loading Ni2P/Cu3P and phosphorus doping on g-C3N4 is effective in overcoming the drawbacks. Phosphorus doping reduces the band gap of g-C3N4 for increased light absorption and improves the separation of photogenerated charge. Additionally, Ni2P/Cu3P heterojunctions anchored on P-doped g-C3N4 (P-C3N4) as non-noble co-catalysts boost light adsorption, enabling charge transfer and speeding the hydrogen evolution process. The resultant Ni2P/Cu3P@P-C3N4 composite photocatalyst achieves an effective photocatalytic hydrogen evolution rate of 201 times greater than that of g-C3N4 (12.9 μmol·h−1·g−1). This work is instructive to develop efficient g-C3N4-based photocatalysts for photocatalytic water splitting without the need for noble metals.

Vacancy-induced spontaneous H2 evolution by overall water splitting on MoTe2/Ti2CO2: A two-dimensional direct Z scheme heterostructure

Photocatalysts with direct Z-scheme heterostructures hold great potential for hydrogen production by solar-driven overall water splitting. However, building highly efficient direct Z-scheme heterostructures is still a challenge. This work develops a novel MoTe2/Ti2CO2 heterostructure as a potential direct Z-scheme photocatalyst for overall water splitting. First-principles computations utilizing density functional theory (DFT) have been used in this study to carefully study several aspects of the heterostructure, including vdW binding energy, formation of the internal electric field, electronic structure, optical properties, and thermodynamic feasibility of water splitting. According to these calculations, the superior interlayer interaction in MoTe2/Ti2CO2 results in a substantial built-in electric field suitable for carrier separation. These findings indicate that the suggested vdW heterostructure is a direct Z-scheme water-splitting photocatalyst with suitable band alignments and a broad light absorption range. This enhanced interaction resulted in a significant increase of photocurrent compared to both the monolayers. Additionally, it is envisaged that the heterojunction will serve as photocatalyst for the oxygen evolution process (OER) and the hydrogen evolution process (HER). The results demonstrate that MoTe2/Ti2CO2 heterostructure with Te vacancy has a low Gibbs free energy of the HER, favoring spontaneous hydrogen evolution in both acidic and neutral conditions. The suggested heterostructure exhibits a commendable solar-to-hydrogen efficiency of 15.25%, making it a viable option for commercial implementation. This research offers a theoretical foundation for designing novel, two-dimensional overall water-splitting photocatalysts in an effort to produce clean energy.

Vacancy engineering in tungsten induced electronic structure optimization of MoSe2 for enhanced electrocatalytic hydrogen evolution reaction

Hydrogen (H2) is a clean and sustainable energy source, and it plays an integral part in lowering the world's reliance on fossil fuels. H2 evolution by the electrocatalytic reduction of water is a key step toward protecting the environment, and the development of cost-effective electrocatalysts is required for the production of huge quantities. In this article, metal (Tungsten)-doped molybdenum selenide (MoSe2) electrocatalysts for the hydrogen evolution process are proposed. MoSe2 activity in the hydrogen evolution process not only promotes the (selenium) Se vacancies and generation of phase shift from 2H to 1T but also optimizes the electronic structure of the material, which is favorable for hydrogen adsorption. Compared to pure P–MoSe2, engineered V–WMoSe2 nanosheets exhibit a low overpotential of ∼247 mV at a current density of 10 mA cm−2 and a lowered Tafel slope and decent turnover frequency (TOF). This technology not only explains the process behind the enhanced hydrogen evolution capabilities but also provides low-cost and effective Mo-based electrocatalysts by stimulating metal cations.

Effect of Sn and Zn alloying with Al on its electrochemical performance in an alkaline media containing CO2 for Al-air batteries application

Aluminum alloyed with other metals, such as Sn and Zn, was synthesized via fusion to trace the impact of alloying elements on the electrochemical characteristics of Al anodes. The corrosion inhibition and electrochemical tests were performed in a 5 M KOH medium in the absence and presence of CO2 for the Al–Sn, and Al–Zn anodes and compared to the commercial aluminum. Tafel polarization exhibited that the anodic and cathodic branches display lower current densities than Al metal in pure KOH. The steady state of the open circuit voltage (Ecorr.) for the studied alloys was shifted to a more negative magnitude than for Al. The corrosion current is sharply decreased, and potential is significantly shifted to less negative values in the presence of CO2. This is due to forming of a protective layer from the carbonate of Al, Sn, and Zn on the surface. Amazing results were obtained and discussed in the case of CO2. Electrochemical impedance spectroscopy (EIS) results exhibited that charge transfer resistance (Rct) values rise with alloying elements. The data of Tafel plots are consistent with those of EIS. The alloying of Al with Sn and Zn elements significantly affects capacitance, hydrogen evolution process suppression, and charge-discharge efficiency. This reveals that the highest potential value in the presence of CO2 in the charging process is obtained for Al–Zn alloy, while the most negative potential is obtained for Al in the discharging process with CO2. Moreover, the discharge time is higher in the alloys than in commercial Al in the absence and more in the presence of CO2. The produced alloys are thought to provide good anodes for long-life rechargeable batteries.

Boosted photocatalytic hydrogen production and photo-Fenton degradation of ciprofloxacin antibiotic over spherical LaMnO3 perovskites assembled boron nitride quantum dots

In this study, boron nitride quantum dots (BNQDs) were assembled on spherical LaMnO3 (LMO) perovskite catalysts to obtain enhanced charge transfer ability during photocatalytic reaction. The photoluminescence and electrochemical measurements indicated that hindered recombination rate and faster migration of photogenerated carriers were achieved after incorporation with BNQDs. The photocatalytic and photo-Fenton catalytic performances of LMO@BNQDs were explored towards degradation of ciprofloxacin antibiotic under visible light irradiation. In the peroxymonosulfate (PMS) activated photo-Fenton system, the degradation performance of the pristine LMO was 47.1% while it was greatly increased to 86.5% after introduction of BNQDs. Based on scavenger tests, superoxide anion radicals were defined as the main active species and the degradation mechanism was proposed. The LMO@BNQDs catalyst also displayed excellent photocatalytic hydrogen production (147 μmol/g H2) which was higher than LMO sample (89 μmol/g). This study aimed to cast light on utilization of BNQDs in both photocatalytic hydrogen evolution and degradation processes.