Potential For Hydrogen Evolution Reaction Research Articles

Tuning Electrocatalytic Activities of Dealloyed Nanoporous Catalysts by Macroscopic Strain Engineering.

It is technically challenging to quantitatively apply strains to tune catalysis because most heterogeneous catalysts are nanoparticles, and lattice strains can only be applied indirectly via core-shell structures or crystal defects. Herein, we report quantitative relations between macroscopic strains and hydrogen evolution reaction (HER) activities of dealloyed nanoporous gold (NPG) by directly applying macroscopic strains upon bulk NPG. It was found that macroscopic compressive strains lead to a decrease, while macroscopic tensile strains improve the HER activity of NPG, which is in line with the d-band center model. The overpotential and onset potential of HER display approximately a linear relation with applied macroscopic strains, revealing an ∼2.9 meV decrease of the binding energy per 0.1% lattice strains from compressive to tensile. The methodology with the high strain sensitivity of electrocatalysis, developed in this study, paves a new way to investigate the insights of strain-dependent electrocatalysis with high precision.

Ce-Doped TiO2 Fabricated Glassy Carbon Electrode for Efficient Hydrogen Evolution Reaction in Acidic Medium.

The quest for sustainable and clean energy sources has intensified research on the Hydrogen Evolution Reaction (HER) in recent decades. In this study, we have presented a novel Ce-doped TiO2 catalyst synthesized through the sol-gel method, showcasing its potential as a superior electrocatalyst for HER in an acidic medium. Comprehensive characterization through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Energy dispersive X-ray (EDX), and Raman spectroscopy confirms the successful formation of the catalyst. Electrocatalytic performance evaluation, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and Tafel analysis, demonstrates that GCE-5wt.%CeTiO2 outperforms bare GCE, as well as Ce and TiO2-based electrodes. Kinetic investigations reveal a Tafel slope of 105 mV dec-1, indicating the Volmer step as the rate-determining step. The onset potential for HER at GCE-5wt.%CeTiO2 is -0.16 V vs. RHE, close to the platinum electrode. Notably, the catalyst exhibits a low overpotential of 401 mV to achieve a current density of 10 mA cm-2 with an impressive 95 % Faradaic efficiency. Furthermore, the catalyst demonstrates outstanding durability, maintaining a negligible increase in overpotential during a 14-hour chronoamperometry test. These results have far-reaching implications for the development of cost-effective and efficient electrocatalysts for hydrogen production.

Sulfur vacancies and group VB metal atoms doping to synergistically optimize hydrogen evolution of MoS2 nanosheets

Molybdenum disulfide (MoS2) based materials exhibit promising potential for hydrogen evolution reaction (HER) performance and stability. Nevertheless, they face key challenges in electrochemical water splitting application as a result of their inert basal planes and limited active sites. On this basis, we attempt to systematically explore the effects of doping group VB metals and introducing sulfur (S) vacancies on improving the inherent conductivity and active sites of MoS2. The experimental consequences show that the catalytic activity of MoS2 doped with group VB metal elements and S-vacancies is significantly different from that of the pure MoS2 samples. In particular, the Nb-doped MoS2 catalyst has better performance than the pure MoS2. Additionally, density functional theory computations further confirm that the synergistic effects of group VB elements and S vacancies enhance the adsorption capacity of hydrogen atoms, resulting in boosting HER performance of the catalysts. The doping of group VB elements can optimize and improve the property of MoS2, which provides a new idea for designing efficient electrocatalysts doped with subgroup elements.

New approach to produce cubic-WC at low temperature for hydrogen evolution reaction

A novel catalyst, a nanostructured cubic-WC (c-WC) flat film, is introduced for the hydrogen evolution reaction (HER) using a specialized magnetron sputtering system. This method results in over 94% crystalline c-WC0.95 formation at room temperature, featuring high-density stacking faults and twin defects. The catalytic performance of the c-WC film for HER is investigated through theoretical simulations and experimental studies. Density-functional theory (DFT) suggests that the c-WC (100) surface exhibits faster reaction kinetics than c-WC (111) surface, approaching the efficiency of Pt (111) surfaces. Experimentally, the c-WC0.95 film exhibits a high electrochemical surface area and increased active sites due to surface defects. Differential electrochemical mass spectrometry (DEMS) confirms an onset potential for HER of −50.0 mV for c-WC0.95 films and establishes electrodesorption as the rate-determining step. Overall, the c-WC film emerges as a cost-effective and efficient catalyst for green hydrogen production, showcasing excellent reproducibility and electrochemical stability.

Highly dispersed palladium nanoparticles decorated on nitrogen doped graphene for enhanced photoelectrochemical water splitting

Among various clear energy generation processes, electrocatalytic water splitting or hydrogen evolution reaction (HER) has been considered as an efficient method for the sustainable production of hydrogen (H2) fuel. But, significant efforts are still required to develop cheap, effective and stable electrocatalysts for water splitting to achieve the economical production of H2. In the quest of finding cheap electrocatalysts, herein, we demonstrate the preparation of palladium (Pd) nanoparticles decorated nitrogen (N) doped highly reduced graphene oxide (NDG-Pd) based electrocatalysts. The nitrogen (N) doped highly reduced graphene oxide (NDG) was produced by using graphene oxide as precursor, which was reduced and doped with nitrogen, simultaneously in one-step hydrothermal method. Subsequently, Pd nanoparticles were decorated on the surface of NDG using a facile ultrasonic method to produce NDG-Pd. In order to restrict the amount of precious metal to reduce the cost of catalysts, very small percentage of Pd, such as, 1 and 3 % was utilized during the preparation of electrocatalysts. The as-prepared electrocatalysts were successfully characterized by using different methods such as, XRD, XPS, EDX, BET, SEM and TEM. Results confirmed the formation of slightly agglomerated, smaller size of Pd NPs on the surface of NDG with an average particle size of ∼ 6 nm. The as prepared nanocomposites NDG, NDG-Pd1% and NDG-Pd3% were used to prepare electrodes and their electrocatalytic activity was evaluated towards the production of H2 through water splitting. The results of electrochemical performance of as-prepared electrodes within the voltage range have revealed that among different samples prepared, the NDG did not show any current, whereas NDG-Pd3% showed a good potential for HER with current density ≈24 mA/cm2 at very low potential i.e. −0.2 V vs RHE.

Potential Use of Waste in Electrocatalysis Using Foundry Sand as Electrocatalyst for the Hydrogen Evolution Reaction

Approximately 13 million tons of foundry sand (FS), a waste from the metallurgic industry, are produced worldwide annually. Although several applications for this waste have been reported, there is a lack of research regarding its application in energy production, such as the hydrogen evolution reaction (HER). Due to several metal oxides commonly present in this waste, like iron oxides, FS may have great potential for HER. Simple carbon-paste electrodes comprised of graphite and FS were prepared and tested for HER. FS, after thermal treatment, showed an onset potential near +0.39 V vs Reversible Hydrogen Electrode and a current density of approximately 16 mA cm‒2 at ‒0.9 V. HER geometric rate, turnover number (TON), and faradaic efficiency were 1.77 μmol h‒1 cm‒2, 3126, and 43.4%, respectively. Those are reasonable values compared to the ones reported in the literature, showing the potential of this waste for the manufacturing of low-cost electrodes.

Solution-processed Sb2Se3 photocathodes under Se-rich conditions and their photoelectrochemical properties.

In this study, selenium (Se)-rich antimony selenide (Sb2Se3) films were fabricated by applying a solution process with the solvents ethylenediamine and 2-mercaptoethanol to optimize the photoelectrochemical (PEC) performance of the Sb2Se3 photocathode. Various antimony (Sb)-Se precursor solutions with different molar ratios of Sb and Se (Sb : Se = 1 : 1.5, 1 : 3, 1 : 4.5, 1 : 7.5, and 1 : 9) were prepared to attain Se-rich fabrication conditions. As a result, the Se-rich Sb2Se3 films fabricated using the Sb-Se precursor solution with a molar ratio of Sb : Se = 1 : 7.5 exhibited an improved PEC performance, compared to the stoichiometric Sb2Se3 film. The charge transport was improved by the abundant Se element and thin selenium oxide (Se2O3) layer in the Se-rich Sb2Se3 film, resulting in a decrease in Se vacancies and substitutional defects. Moreover, the light utilization in the long wavelength region above 800 nm was enhanced by the light-trapping effect because of the nanowire structure in the Se-rich Sb2Se3 film. Hence, the optimal Se-rich Sb2Se3 photocathodes showed an improved photocurrent density of -0.24 mA cm-2 at the hydrogen evolution reaction potential that was three times higher than that of the stoichiometric Sb2Se3 photocathodes (-0.08 mA cm-2).

High-density defect-induced ultrahigh boron and nitrogen doping of iron–copper-functionalized porous carbon nanosheets for enhanced water splitting

The high cost of precursors and the complexity of synthesis procedures have hindered the widespread use of two-dimensional (2D) porous carbon nanosheets in water splitting. In this study, we successfully developed a low-cost method for the rapid synthesis of three-dimensional (3D) hierarchically porous architectures self-assembled from iron–copper nanoparticles embedded in boron (B)/nitrogen (N)-codoped 2D porous carbon nanosheets (denoted as FeCu@BNPCNS). The optimal FeCu@BNPCNS-900 nanosheet exhibited a large surface area, abundant porous channels, meso/macropores, and carbon edges/defects. Particularly, 10.25 atom% of B/N electrochemically active centers (such as pyridinic-N (including the metal–nitrogen–carbon species), pyrrolic-N, graphitic-N, and BC3) were successfully doped into the optimal FeCu@BNPCNS-900 nanosheets. In an alkaline solution, FeCu@BNPCNS-900 exhibited excellent electrocatalytic activity for hydrogen evolution reaction (HER), which was higher than that of the commercial 20 wt% Pt/C. For example, the HER potential of FeCu@BNPCNS-900 at 10 mA cm−2 [E10; −202.3 mV vs. reversible hydrogen electrode (RHE)] was only 140.2 mV more negative than that of 20 wt% Pt/C (−62.1 mV vs. RHE). Additionally, FeCu@BNPCNS-900 exhibited a slightly lower oxygen evolution reaction (OER) electrocatalytic activity than the ruthenium oxide (RuO2). Particularly, the OER E10 potential (+1.634 V vs. RHE) of FeCu@BNPCNS-900 was only 76 mV more positive than that of RuO2 (+1.558 V vs. RHE). The FeCu@BNPCNS-900||FeCu@BNPCNS-900 cell achieved 10 mA cm−2 at 1.613 V, which was 58 mV more negative than that of the 20 wt% Pt/C||RuO2 cell (1.671 V). The excellent water-splitting performance of FeCu@BNPCNS-900 could be attributed to the 3D hierarchically porous architecture, abundant channels/mesopores, and uniformly dispersed electrocatalytically active sites. Therefore, we developed an efficient strategy for the large-scale and low-cost synthesis of 2D porous carbon nanosheets without the need for precursors, templates, or surfactants.

Study on effect of vanadium doping in cesium tungsten bronze system and application in HER

Increasing demand for energy and the crisis of fossil fuels have led researchers to search for an alternative energy source. Hydrogen is the cleanest energy source producing water as fuel cells exhaust. However, producing hydrogen could be crucial as only some active catalysts produce pure hydrogen. The expense due to the scarcity of the state-of-the-art catalyst (platinum) for the Hydrogen Evolution Reaction (HER) is the main reason for the higher price of pure hydrogen as a fuel. In our present research, we chose the less expensive cesium tungsten bronzes (CTB) doped with various percentages of vanadium (5 mol% - 20 mol%) to study their HER performance. The materials were prepared hydrothermally at 180 °C at different reaction times. XRD revealed that, upon increasing the vanadium amount, the hexagonal phase of the CTB is transformed to the cubic phase at a higher reaction time. However, the hexagonal phase was retained after vanadium introduction with a lower reaction time. FT-IR, Raman, EDX, SIMS, XPS, and XRF spectroscopy confirmed the incorporation of vanadium into the bronze system. Vanadium-doped samples showed enhanced HER activity compared to the pure CTB. The 20% vanadium-doped hexagonal bronze showed the best HER performance in 0.5 M H2SO4 among all the vanadium-doped materials, which lowered the HER potential of the pure CTB (-0.665 V vs RHE) to -0.288 V vs RHE at -10 mA cm−2. This increase in activity was correlated with a higher surface area, higher electrochemical surface area, faster reaction kinetics with a lower Tafel slope, and a small charge-transfer resistance of the samples after V5+ incorporation compared to the pure CTB.

Enhanced hydrogen production via urea electrolysis over Ni-NiO electrodeposited on Ti mesh

The sluggish kinetics of anodic oxygen evolution reaction (OER) is regarded as the main bottleneck for ineffective hydrogen production efficiency, limiting the industrial application of electrochemical water splitting. Substituting the OER by urea electrooxidation reaction (UOR) and simultaneously developing highly active and economical bifunctional electrocatalyst for UOR and hydrogen evolution reaction (HER) is a promising method to realize energy-saving hydrogen production and urea-rich wastewater abatement. Herein, self-supporting Ni-NiO film grown on Ti mesh (Ni-NiO/TM) was successfully prepared by a facile cathodic electrodeposition method with using nickel acetate as the only raw material. Electrodeposition process was optimized by modulating the electrodeposition time and potential. x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and Raman characterization revealed the optimized Ni-NiO/TM was comprised of crystalline Ni and amorphous NiO and its morphology exhibited nanosphere structure, assembled by nanosheets. Ni-NiO/TM sample prepared under the potential of −1.5 V and deposition time of 10 min illustrated the lowest UOR potential of 1.34 V at 50 mA cm−2 and robust stability, superior to the recently reported literatures. Furthermore, the HER potential was only −0.235 V to drive the current density of 50 mA cm−2. The cell voltage of urea-assisted electrolysis for hydrogen production in Ni-NiO/TM||Ni-NiO/TM two-electrode system only required 1.56 V to deliver 50 mA cm−2, obviously lower than that (>1.72 V) for overall water splitting. This work demonstrated the potential of Ni-based material as bifunctional electrocatalyst for energy-saving H2 production by urea-rich wastewater electrolysis.

Facile synthesis of ultrafine iron-cobalt (FeCo) nanocrystallite-embedded boron/nitrogen-codoped porous carbon nanosheets: Accelerated water splitting catalysts

Designing two-dimensional (2D) porous carbon nanosheets is expected to boost the water splitting efficiency of low-cost iron (Fe) and cobalt (Co)-based catalysts. Nevertheless, the aggregations, tedious preparation procedures, and expensive precursors for synthesizing 2D porous carbon nanosheets have hindered their widespread application. Herein, for the first time, we developed a low-cost method for large-scale and rapid synthesis of the three-dimensional (3D) hierarchically porous architectures self-assembled by the ultrafine FeCo nanoparticles embedded and boron/nitrogen-codoped 2D porous carbon nanosheets (denoted as FeCo@BNPCNS). The optimal FeCo@BNPCNS-900 exhibited abundant porous channels, a large surface area, and vast carbon edges/defects. Therefore, 8.10 at% electrochemically active boron (B)/nitrogen (N) centers were doped into the porous carbon nanosheets. In an alkaline solution, the optimal FeCo@BNPCNS-900 nanosheets revealed excellent hydrogen evolution reaction (HER) electrocatalytic activity, surpassing commercial 20 wt% Pt/C. For instance, the HER potential at 10 mA cm−2 [-50.6 mV vs. reversible hydrogen electrode (RHE)] of FeCo@BNPCNS-900 was even 19.3 mV more positive than that of commercial 20 wt% Pt/C (-69.9 mV vs. RHE). Meanwhile, its oxygen evolution reaction (OER) catalytic activity was just a little worse than ruthenium oxide (RuO2). The water electrolysis cell of FeCo@BNPCNS-900 nanosheets just required a small voltage of 1.589 V for full water splitting to achieve 10 mA cm−2, even 70.3 mV more negative than that of the state-of-the-art 20 wt% Pt/C||RuO2 benchmark (1.660 V) with outstanding stability. The perfect 3D hierarchically porous and honeycomb-like architecture, abundant porous channels/mesopores, and uniformly dispersed electrocatalytically active sites on FeCo@BNPCNS-900 nanosheets were responsible for the outstanding water splitting performance. Finally, this study provides an efficient strategy for the large-scale, rapid, and low-cost synthesis of 2D porous carbon nanosheets without using any template, surfactant, or expensive precursors.

Engineering Double Sulfur-Vacancy in CoS1.097@MoS2 Core-Shell Heterojunctions for Hydrogen Evolution in a Wide pH Range.

Heterostructured nanomaterials have arisen as electrocatalysts with great potential for hydrogen evolution reaction (HER), considering their superiority in integrating different active components but are plagued by their insufficient active site density in a wide pH range. In this report, double sulfur-vacancy-decorated CoS1.097@MoS2 core-shell heterojunctions are designed, which contain a primary structure of hollow CoS1.097 nanocubes and a secondary structure of ultrathin MoS2 nanosheets. Taking advantage of the core-shell type heterointerfaces and double sulfur-vacancy, the CoS1.097@MoS2 catalyst exhibits pH-universal HER performance, achieving the overpotentials at 10 mA cm-2 of 190, 139, and 220 mV in 0.5 M H2SO4, 1.0 M KOH, and 1.0 M PBS, respectively. Systematic theoretical results show that the double sulfur-vacancy can endow the CoS1.097@MoS2 core-shell heterojunctions with promoted electron/mass transfer and enhanced reactive kinetics, thus boosting HER performance. This work clearly demonstrates an indispensable role of double sulfur-vacancy in enhancing the electrocatalytic HER performance of core-shell type heterojunctions under a wide pH operating condition.

Trimetallic CuO/Ag/NiO supported with silica nanoparticles based composite materials for green hydrogen production

Production and utilization of grey and blue hydrogen is responsible for emission of millions of tons of carbon dioxide (CO2) across the globe. This increased emission of CO2 has severe repercussions on the planet earth and in particular on climate change. Here in, we explored advance bimetallic (BM) CuO/Ag and trimetallic (TM) CuO/Ag/NiO based nanoporous materials supported with silica nanoparticles (SiNPs) via sol–gel route. The explored nanocatalysts were characterized by Powder X-ray diffraction (P-XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and Raman spectroscopic techniques. These advance nanocatalysts were evaluated for the green hydrogen production through electrocatalysis and photocatalysis. The catalysts exhibited an exceptional catalytic performance, the onset potential for hydrogen evolution reaction (HER) was determined to be − 0.9 V BMSiNPs-GCE and − 0.7 V (vs Ag/AgCl) for TMSiNPs-GCE, whereas η@10 for BMSiNPs-GCE and TMSiNPs-GCE is − 1.26 and − 1.00 V respectively. Significantly, the TMSiNPs composite and the BMSiNPs composite exhibited superior photochemical H2 evolution rates of 1970.72 mmol h−1 g−1 and 1513.97 mmol h−1 g−1, respectively. The TMSiNPs catalyst presents a highly promising material for HER. This study reveals a cost-effective approach to develop sustainable and resourceful electrocatalysts for HER.

Efficient Electrocatalytic Hydrogen Evolution Reaction on CuO Immobilized Stainless‐Steel Electrode Prepared by the SILAR Method

AbstractThe development of cost‐effective and efficient catalysts for the hydrogen evolution reaction (HER) has been a subject of intense research for sustainable and clean energy in recent decades. For this purpose, CuO‐modified stainless steel (CuO‐SS) electrode was fabricated to attain HER in acidic media. Here in, CuO film was fabricated on a stainless steel (SS) surface following successive ionic layer adsorption and reaction (SILAR) method. A 60‐cycle CuO modification resulted in enhanced HER activity compared to the bare SS or CuO electrode with an average 99 % Faradic efficiency. Based on the Electrochemical Impedance Spectroscopy (EIS), at an HER potential, the bare SS electrode exhibited charge transfer resistance of 24.7 Ω whereas CuO‐SS electrode exhibited 6.47 Ω only. The overpotential was calculated to be 154 mV at the CuO‐SS electrode regarding HER. The results have significant implications for the development of cost‐effective and efficient electrocatalysts for hydrogen production.

Control of the metal-support interactions in Ru on N-doped graphene-encapsulated Ni nanoparticles to promote their hydrogen evolution reaction catalytic performance

Controlling metal-support interaction (MSI) is considered as an effective strategy to optimize the electronic structure of catalysts and thus promote their catalytic performance. Here, with the strong MSI by both metal core and nitrogen-doped carbon shell, the synthesized Ru supported on N-doped graphene-encapsulated Ni nanoparticles (Ni@NC/Ru) show excellent performance towards hydrogen evolution reaction (HER). It exhibits a very low HER potential of 28 mV at the current density of 10 mA cm−2, and high durability that the potential only increases approximately 7 mV after 10,000 cyclic voltammetry cycles. The high HER performance is attributed to the strong MSI from the tuning effect of Ni metal core and N-dope graphene shell, which optimizes the hydrogen binding energy of the catalysts. This study may shed light on the rational design of superior HER catalysts.

Laser ablated uniform deposition of bismuth oxide film as efficient anode for zinc based flow battery

Zinc based redox flow batteries are the most proficient and attractive candidature for large scale energy storage applications. However, zinc dendritic formation and inhomogeneous deposition of zinc hamper the cyclability of zinc-based flow batteries. Herein, we have successfully decorated Bi2O3 on the felt by using the pulsed laser deposition (PLD) technique and tested it as a negative electrode in zinc bromine redox flow battery. The Bi2O3 felt provides more robust nucleation sites for zinc nuclei, lowers the potential of hydrogen evolution reaction, minimizes the surface diffusion of zinc, lowers zinc nucleation overpotential, and triggers homogenous zinc deposits. Compared to pristine (57.7 %), Bi2O3 felt exhibited an energy efficiency of 70.6 % at 100 mA cm−2. Interestingly, the morphological evolution of zinc deposits demonstrates that zinc deposition on the Bi2O3 felt is more homogeneous than pristine at an initial time (30 sec of charging at 20 mA cm−2). Moreover, Bi2O3 felt shows a stable long cycling performance over 200 cycles with minimized charge discharge overpotential and exhibited an avg. coulombic efficiency of 96.78 % which is superior than pristine. Thus, Bi2O3 felt is a prominent anode material for improving the electrochemical performance of zinc based redox flow batteries.

Cobalt nanoparticles-embedded porous carbon nanocages uniformly dispersed hollow carbon fibers as the accelerated electrocatalysts toward water splitting

The fast, low-cost, and efficient design of zeolite imidazolate frameworks (ZIF) based derivatives with perfect hollow channels is an effective method for enhancing their full water-splitting catalytic activities and achieving their commercial use. In this study, the novel cobalt nanoparticles embedded in nitrogen-doped porous carbon nanocages uniformly dispersed over two curved surfaces of biomass-derived hollow carbon fibers (Co@NC nanocage/HCF) were synthesized via the carbonization of the ZIF-67/hollow biomass fiber precursors. After the usage amounts of biomass fibers were optimized, the optimal Co@NC nanocage/HCF200 exhibited a larger surface area and higher dispersion states of Co@NC nanocages than the tightly packed pure Co@NC nanocages. Particularly, owing to the hollow and porous structures of Co@NC nanocages, more electrocatalytic active centers (i.e. the pyridinic-N, Co-Nx-C, pyrrolic-N, graphitic-N, high-valence Co, and other oxygen-containing functional groups) were exposed along surfaces of the Co@NC nanocage/HCF200 catalyst. In an alkaline solution, the hydrogen evolution reaction potential at 10 mA cm−2 for Co@NC nanocage/HCF200 was 165 mV more negative than that of 20 wt% Pt/C. Particularly, the oxygen evolution reaction potential at 10 mA cm−2 for Co@NC nanocage/HCF200 was 17 mV more negative than that of RuO2. For overall water splitting, the bifunctional Co@NC nanocage/HCF200 catalyst-based electrolysis cell achieved a current density of 10 mA cm−2 at a cell voltage of 1.618 V, which is 4 mV smaller than that of the state-of-the-art 20 wt% Pt/C||RuO2 cell (1.614 V). The perfect hollow and porous structures, uniformly dispersed Co@NC nanocages (locked by vast in situ formed carbon nanotubes), and abundant electrocatalytic active sites along the inner and outer surfaces of Co@NC nanocage/HCF200 contributed to the excellent water splitting catalysis. Particularly, owing to the excellent stabilities of hollow structures and uniformly dispersed porous Co@NC nanocages, the Co@NC nanocage/HCF200 exhibited higher stability toward water electrolysis.

Effect of phosphorization temperature on the structure and hydrogen evolution reaction performance of nickel cobalt phosphide electrocatalysts

Nickel cobalt phosphides electrocatalysts have shown great potential for hydrogen evolution reaction (HER) but further improvements are necessary. Here, nickel cobalt phosphide nanosheets were synthesized via electrodeposition followed by phosphorization methodology. The relationships between phosphorization temperature and the structure or hydrogen evolution reaction (HER) activity were studied. The catalyst phosphated at 350 °C (NiCoP-350/CC) displayed excellent HER performance in alkaline media with a low overpotential of 59 mV at the current density of 10 mA cm−2 (η10 = 59 mV). This could be attributed to the formation and better dispersion of active NiCoP crystalline phase on the surface of carbon cloth.

Boosting electrochemical nitrogen reduction performance through water-in-salt electrolyte

While electrochemical nitrogen reduction reaction (NRR) stands as a promising technique for sustainable NH3 fabrication due to its mild operation conditions, it has long been suffered from low efficiency and poor selectivity owing to the inertness of N2 and competition hydrogen evolution reaction (HER). Herein, we report the use of oxygen vacancy rich TiO2 loaded with Au nanoparticles as NRR catalyst in super concentrated lithium bis(trifluoromethane sulfonyl) imide (Li TFSI) “water-in-salt” system (20 M electrolyte) and obtain the Faradaic efficiency of 37.2 % with an NH3 yield rate of 20.3 μg h−1 cm−2 at − 0.4 V vs RHE, accompanied by the significant decay of both current density and onset potential of hydrogen evolution reaction. Electrochemical experimental and theoretical calculation results indicate that the HER process can be greatly hindered both kinetically and energetically. The unique effect of this “water-in-salt” electrolyte would offer a new idea to improve the NRR selectivity via HER suppression.

Constructing porous boron doped nickel phosphide (Ni2P) rod arrays with optimized electron coordination for alkaline hydrogen evolution

Transition metal-based phosphides (TMPs) show great potential for hydrogen evolution reaction (HER). The fine regulation of the electronic structure of metal-rich phosphides is an effective and challenging strategy for better activity. Herein, a simple and effective molten salt treatment is designed to synthesize porous boron doped Ni2P rod nanoarrays (M-B-Ni2P) for alkaline HER. The molten salt treatment facilitates the formation of unique porous Ni2P rod nanoarrays with homogeneous boron doping. The synthesized porous M-B-Ni2P exhibit excellent catalytic performance in alkaline media, requiring only an overpotential of 217 mV to drive 100 mA cm−2, which is 79 mV lower than binary nickel phosphide (M-Ni2P). The boron doping not only optimizes the porous geometry to increase the number of active sites, but also regulates the electronic coordination to promote the dissociation of water and the adsorption and desorption of hydrogen atoms. In addition, the self-supported monolithic M-B-Ni2P electrode can operate at a larger current density of 100 mA cm−2 for at least 100 h. This study on realizing boron doping based on molten salt treatment provides a new strategy for constructing transition metal-based phosphides as electrocatalysts.