Ni Foam Substrate Research Articles

Enhanced electrocatalytic efficiencies for water electrolysis and para-nitrophenol hydrogenation by self-supported nickel cobalt phosphide-nickel iron layered double hydroxide p-n junction

Charge redistribution across heterointerfaces is an important tactic to enhance the catalytic activities and bifunctionality of hybrid catalysts, especially for green hydrogen production from water electrolysis and harmless electrocatalytic valorization of organics. Herein, a self-supported p-n junction catalytic electrode was constructed by tandem electrodeposition of nickel cobalt phosphide (NiCoP) and nickel iron layered double hydroxide (NiFe LDH) onto Ni foam (NF) substrate, denoted as NiCoP@NiFe LDH/NF, to enhance the electrocatalytic capabilities for water electrolysis and hydrogenation of an organic, para-nitrophenol (4-NP). Benefitting from the charge redistribution across the p-n junction, high electrocatalytic efficiencies for oxygen evolution reaction (OER, overpotential of 388 mV at 100 mA cm−2) and hydrogen evolution reaction (HER, overpotential of 132 mV at 10 mA cm−2) could be achieved concurrently by the NiCoP@NiFe LDH/NF electrode, and both overpotentials were located within the mainstream levels in this domain. The bifunctional catalytic features enabled a full water electrolysis response of 10 mA cm−2 at 1.61 V. In addition, the p-n junction electrode catalyzed the hydrogenation of 4-NP at a conversion of 100%, para-aminophenol (4-AP) selectivity of 90% and faradaic efficiency (FE) of 88% at −0.18 V. The current work offers a feasible strategy for fulfilling electrochemical H2 production and hydrogenation valorization of 4-NP pollutant by constructing a self-supported p-n junction catalytic electrode.

Constructing P-CoMoO4@NiCoP heterostructure nanoarrays on Ni foam as efficient bifunctional electrocatalysts for overall water splitting

Improving catalytic activity and durabilty through the structural and compositional development of bifunctional electrocatalysts with low cost, high activity and stability is a challenging issue in electrochemical water splitting. Herein, we report the fabrication of heterostructured P-CoMoO4@NiCoP on a Ni foam substrate through interface engineering, by adjusting its composition and architecture. Benefitting from the tailored electronic structure and exposed active sites, the heterostructured P-CoMoO4@NiCoP/NF arrays can be coordinated to boost the overall water splitting. In addition, the superhydrophilic and superaerophobic properties of P-CoMoO4@NiCoP/NF make it conducive to water dissociation and bubble separation in the electrocatalytic process. The heterostructured P-CoMoO4@NiCoP/NF exhibits excellent bifunctional electrocatalysis activity with a low overpotential of 66 ​mV at 10 ​mA ​cm−2 for HER and 252 ​mV at 100 ​mA ​cm−2 for OER. Only 1.62 ​V potential is required to deliver 20 ​mA ​cm−2 in a two-electrode electrolysis system, providing a decent overall water splitting performance. The rational construction of the heterostructure makes it possible to regulate the electronic structures and active sites of the electrocatalysts to promote their catalytic activity.

Revealing the potential of hierarchical heterostructure of tri-metallic selenide and MOFs etched layered hydroxide dodecahedron laminated with rGO-Ni foam for a hybrid supercapacitor applications

Inaugurating the multistage hierarchical hybrid structure with ample surface area and synergistic contribution from polymetallic selenide and layered hydroxide in a conductive 3D substrate has been supposed to be appealing and highly-rated electrode material to enhance the general electrochemical parameters of supercapacitors (SCs), thanks to exclusive structural features, immense electronic states and relatively paramount electrical conductivity of the final product. In this work, hydrothermal assisted zinc‑nickel‑cobalt-selenide (ZNC-Se) nanosheets have been uniformly prepared onto the conductive rGO decorated Ni foam substrate, chased by uniform decoration of metal organic frameworks (MOFs) templated nickel‑cobalt-layered double hydroxide (NC-LDH) onto tri-metallic (ZNC-Se) nanosheets to achieve the hierarchical hybrid structure of [email protected]@rGO-NF. The as-prepared hierarchical [email protected]@rGO-NF delivers remarkable specific capacity value along with outstanding cycle stability. The proposed [email protected]@rGO-NF and MOFs derived open and hollow carbon structure (MDOHCS)-based hybrid device disclosed remarkable cyclic life and an energy/power density of 80.3 W h kg−1/15970.9 W kg−1.

Autonomous Catalyst Development for Alkaline Electrolysis

NiFe LDH based materials are promising candidates for cheap, high performance catalysts for alkaline OER. While suffering from degradation effects, the presence of Fe, even in trace amounts, increases their OER activity manifold compared to plain Ni hydroxide. Although discovered in the mid-80s, the exact catalytic mechanism of this “Fe effect” is still not fully understood. Additionally, other doping elements like Co, Cr, Al and others have shown to both further improve OER activity and increase stability. The properties of those materials are often highly dependent on the doping ratio, resulting in an enormous number of possible material combinations. Modern techniques like DFT simulations and machine learning can help to speed up the search for the optimal compositions, but ultimately manual experimentation often limits how fast better materials can be discovered, as the process remains both resource and time-consuming.In this work, we combine an autonomous high-throughput experiment with machine learning assisted optimization of material compositions to a closed-loop system in an attempt to substantially accelerate the search for high performance alkaline OER catalysts. The system screens an eight variable phase space of doped NiFe LDH for compositions that yield optimal OER performance. Its centerpiece is a 4-axis robotic arm from North Robotics with sample, vial and liquid handling capabilities. The samples are prepared by means of a dip-coating process on Ni foam substrates that allows for doping with different metals. Electrochemical investigations are carried out in 1M KOH in an automated test cell, including EIS, CV and CP measurements at current densities of up to 200mA/cm2. From these results, a figure of merit for the OER activity is calculated and fed into a bayesian optimizer (Dragonfly). This algorithm determines the most promising next test candidate based on the principles of exploration and exploitation and initiates the next experiment accordingly. The experimental procedure can be divided into independent sub-steps, allowing for smart scheduling. This can reduce downtime of the robotic arm and therefore increase the throughput significantly, such that up to 1000 experiments per week can be achieved.We present the first results of a screening study conducted with this system and compare it to a manual study in terms of accuracy, reproducibility and throughput. Selected, particularly high performing compositions found in this study are also tested in a flow cell setup under industrially relevant conditions (30 wt. % KOH, 60 °C) for several hundred hours.

Investigation of Ni Foam and Stainless-Steel Mesh Substrates Toward Oxygen Evolution Reaction in Alkaline Seawater Electrolysis

Electrolysis of alkaline seawater is a promising approach for the large-scale production of hydrogen, however, little effort has been devoted in studying the substrates for oxygen evolution reaction (OER) electrocatalysts. Stainless-steel mesh (SS mesh) and Ni foam were investigated systematically for OER in alkaline seawater electrolysis in this study. The overpotentials and Tafel slopes with SS meshes are smaller than Ni foams. Interestingly, the performance of the SS mesh even outperforms various non-noble metal electrocatalysts and is comparable to commercial RuO2 and IrO2 catalysts. Additionally, the Ni foam exhibits much poorer resistance to corrosion compared with SS meshes. This work suggests inexpensive and commercially available SS mesh is an outstanding substrate for OER in alkaline seawater electrolysis.

Activating Nickel-Molybdenum Electrocatalyst Via Copper-Element Modification Toward 1 A cm−2 Hydrogen Evolution in Non-Extreme pH Carbonate Buffer Electrolyte

Water electrolysis driven by renewable electricity produces green hydrogen, which will play a pivotal role in realizing a sustainable society. However, the production cost of green hydrogen is currently $5.3/kg, nearly four times higher than $1.4/kg of grey hydrogen,[1] which necessitates the reduction of green hydrogen cost toward its large-scale deployment. While reducing electrolyzer cost is one of the key interventions,[2] extremely acidic or alkaline conditions in currently commercialized electrolyzers require expensive corrosion-tolerant materials as the components, which hinders further reduction of electrolyzer cost. In this sense, non-extreme pH water electrolyzer can be innovative technology because its milder conditions than those in currently commercialized electrolyzers potentially enable the use of cheap and abundant materials (such as Fe or stainless steel) as electrolyzer components (such as frame or bipolar plate),[3] which can reduce the electrolyzer cost and, in the end, production cost of green hydrogen. Non-extreme pH electrolysis was reported to suffer inferior performance compared to those in extreme pH conditions.[4] However, our previous study using nickel and iron-based anode in potassium carbonate buffer solution at pH 10.5 achieved high oxygen evolution reaction (OER) performances comparable to those of highly alkaline OER,[5] which should be followed by the development of highly effective cathode for hydrogen evolution reaction (HER) to realize the highly efficient non-extreme pH electrolyzer.The present study reports on our discovery of the nickel and molybdenum-based electrocatalysts that efficiently catalyze HER in carbonate buffer electrolyte at pH 10.5. First of all, visibly flat films of nickel (Ni), molybdenum oxide (MoOx), and nickel molybdenum oxide (NiMoOx) were prepared by cathodic electrodeposition on rotating disk electrodes. Their electrocatalytic testing revealed that, as in alkaline conditions, the coexistence of Ni and Mo is required to achieve high catalytic activity even in K-carbonate solution at pH 10.5. Subsequently, a variety of transition metal elements (manganese, cobalt, copper, and tungsten) were introduced into NiMoOx via co-electrodeposition onto Ni foam substrate to further enhance the HER performance. Among the developed electrodes, NiMoOx modified with copper element (NiMoOx(Cu)) was the best and achieved 1 A cm−2 at an overpotential of ca. 0.2 V, which is comparable to those of previously reported HER in highly alkaline conditions (Figure 1). Our characterization revealed that Cu addition into NiMoOx made the surface structure to be rougher and led to the largest double-layer capacitance, both of which indicate the enlarged active surface area. Besides, the presence of Cu element decreased the apparent Tafel slope, suggesting the tailored nature of active site, which was consistent with the shift of Ni and Mo peaks in ex situ X-ray photoelectron spectroscopy (XPS) analysis. Finally, combined with previously developed nickel and iron-based anode[5] and carefully selected polyether sulfone (PES) diaphragm, overall cell performance was elevated in 3.0 mol kg−1 K-carbonate solution at pH 10.5 and 353 K. The resultant cell performance including the series resistance achieved 1 A cm−2 at a voltage of merely ca. 2.0 V, competitive to those of top-class commercial alkaline electrolyzers. These findings demonstrate the potential of non-extreme pH electrochemical electrolyzers in industrial applications.Reference[1] “Finding the sea of green”, EDISON, 2021.[2] M. Chatenet, et al., Chem. Soc. Rev. 2022, 51, 4583.[3] M. Pourbaix, “Atlas of Electrochemical Equilibria in Aqueous solutions”, 1974.[4] T. Naito, et al., ChemSusChem 2022, 8, e202102294.[5] T. Nishimoto, et al., ChemSusChem 2022, e202201808. Figure 1

Rational Design of a Copper Cobalt Sulfide/Tungsten Disulfide Heterostructure for Excellent Overall Water Splitting.

Integrating different components into a heterostructure is a novel approach that increases the number of active centers to enhance the catalytic activities of a catalyst. This study uses an efficient, facile hydrothermal strategy to synthesize a unique heterostructure of copper cobalt sulfide and tungsten disulfide (CuCo2S4-WS2) nanowires on a Ni foam (NF) substrate. The nanowire arrays (CuCo2S4-WS2/NF) with multiple integrated active sites exhibit small overpotentials of 202 (299) and 240 (320) mV for HER and OER at 20 (50) mA cm-2 and 1.54 V (10 mA cm-2) for an electrolyzer in 1.0 M KOH, surpassing commercial and previously reported catalysts. A solar electrolyzer composed of CuCo2S4-WS2 bifunctional electrodes also produced significant amounts of hydrogen through a water splitting process. The remarkable performance is accredited to the extended electroactive surface area, reasonable density of states near the Fermi level, optimal adsorption free energies, and good charge transfer ability, further validating the excellent dual function of CuCo2S4-WS2/NF in electrochemical water splitting.

Janus photoelectrocatalytic filter for sustainable water decontamination

Herein, we conceive a Janus photoelectrocatalytic filter (Sb-Fe/MXene) by depositing Sb single-atoms (Sb-SA) and Fe nanoclusters (Fe-NC) decorated MXene mixture on either side of Ni-foam substrate, respectively, which realized sustainable and efficient generation of hydrogen peroxide (H2O2) and hydroxy radical (•OH) without any chemicals input. Photocatalytic-side ensures that the accumulated holes at Ti vacancies neighboring the Sb-SA promote the 4e− water oxidation reactions to produce O2, while the Sb-SA sites collect electrons forming reducing centers for non-sacrificial H2O2 production via the 2e− oxygen reduction reaction. Electrocatalytic-side guarantees the circulation of ≡ Fe(III)/≡ Fe(II) by continuously exposing “fresh” reactive sites by dissociating H2O2 on the ≡ Fe(II). This further prohibits iron sludge accumulation with an enhanced remedy of micropollutants, even under neutral conditions for wastewater. The collaborative effect between photochemistry and electrochemistry establishes a strategy for energy conversion and environmental remediation using a Janus photoelectrocatalytic filtration system.

Enhancing the electrochemical activity of zinc cobalt sulfide via heterojunction with MoS2 metal phase for overall water splitting

The integration of diverse components into a single heterostructure represents an innovative approach that boosts the quantity and variety of active centers, thereby enhancing the catalytic activity for both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) in the water splitting process. In this study, a novel, hierarchically porous one-dimensional nanowire array comprising zinc cobalt sulfide and molybdenum disulfide (MoS2@Zn0.76Co0.24S) was successfully synthesized on a Ni foam substrate using an efficient and straightforward hydrothermal synthesis strategy. The incorporation of the metallic phase of molybdenum disulfide elevates the electronic conductivity of MoS2@Zn0.76Co0.24S, resulting in impressively low overpotentials. At 20, 50, and 100 mA cm−2, the overpotentials for oxygen evolution reaction (OER) are merely 90 mV, 170 mV, and 240 mV, respectively. Similarly, for hydrogen evolution reaction (HER), the overpotentials are 169 mV, 237 mV, and 301 mV at the same current densities in 1.0 M potassium hydroxide solution. The utilization of the MoS2@Zn0.76Co0.24S /NF electrolyzer demonstrates its exceptional performance as a catalyst in alkaline electrolyzers. Operating at a mere 1.45 V and 10 mA cm−2, it showcases outstanding efficiency. Achieving a current density of 405 mA cm−2, the system generates hydrogen at a rate of 3.1 mL/min with a purity of 99.997%, achieving an impressive cell efficiency of 68.28% and a voltage of 1.85 V. Furthermore, the MoS2@Zn0.76Co0.24S /NF hybrid exhibits seamless integration with solar cells, establishing a photovoltaic electrochemical system for comprehensive water splitting. This wireless assembly harnesses the excellent performance of the hybrid nanowire, offering a promising solution for efficient, durable, and cost-effective bifunctional electrocatalysts in the realm of renewable energy.

Enhanced selective nitrate-to-nitrogen electrocatalytic reduction by CNTs doped Ni foam/Cu electrode coupled with Cl−

In this work, a Ni foam/CNTs/Cu composite electrode was prepared via the impregnation and electrodeposition methods. The electrode enhanced the total nitrogen removal and N2 selectivity, when served as a cathode for NO3−-N reduction. SEM, EDS, XRD, and XPS characterization revealed that both CNTs and metallic copper were introduced onto the surface of the Ni foam substrate successfully. Besides, the LSV, CV, EIS and Cdl results indicated more electrochemical active sites were in the Ni foam/CNTs/Cu electrodes than in Ni foam/Cu electrodes. Under optimal preparation conditions, the Ni foam/CNTs/Cu electrode showed N2 selectivity of 68.89 % and nitrate removal rate of 96.75 % in 100 mg/L nitrate solution with Na2SO4 as electrolyte. The selectivity of N2 could be significantly enhanced by adding Cl− as electrolyte, and the nitrogen selectivity increased with the increase of Cl− concentration. At 1.25 g/L NaCl, the Ni foam/CNTs/Cu electrode could achieve >95 % nitrate and total nitrogen removal and close to 100 % N2 selectivity. The N2 selectivity of the Ni foam/CNTs/Cu electrode was 2.534 and 1.8 times of the Ni foam/Cu electrode when 0.5 g/L Na2SO4 and 0.5 g/L NaCl were used as electrolytes, respectively. Consequently, to achieve the same nitrate reduction effect, the Ni foam/CNTs/Cu electrode could reduce the amount of NaCl compared with Ni foam/Cu electrode. The electrodes were tested in 6 cycles and proved to be stable. At last, a potential mechanism of nitrate‑nitrogen removal by the electrocatalytic process was suggested.

Enhanced water oxidation reaction by binder-free nickel oxide nanorod arrays electrocatalyst

Water splitting for hydrogen generation is one of the auspicious technologies for the sustainable resource storage and designing low cost electrocatalysts with high activity and is considerable to ameliorate the slow kinetic process of oxygen evolution reaction (OER). Accordingly, in this work, an experimental investigation for the improved water oxidation reaction based on the nickel oxide (NiO) nanorod arrays structure electrocatalyst is performed for the hydrogen production reaction. In this context, a highly efficient functional electrocatalyst is developed by morphology engineering for the growth of NiO nanorod arrays on Ni foam (NF) substrate (NiO–NF electrocatalyst) as an anode. The electrode is prepared by utilizing the hydrothermal method under the optimized experimental conditions (heating temperature of 100 °C and reaction time of 12 h in atmosphere). The electrochemical performance of the fabricated electrode is studied in an alkaline solution of 1.0 M KOH, and the obtained results revealed that only +350/+450 mV with/without iR-Correction is required to reach a current density of 100 mA cm−2, showing an effective electrocatalyst for water oxidation. The low charge-transfer resistance of the electrocatalyst (∼ 5 Ω) indicates favorable catalytic dynamics during OER. Notably, the electrocatalyst demonstrates outstanding durability during rigorous oxygen evolution testing in 1.0 M KOH for 100 h with ∼ 98% Faradaic efficiency. Additionally, the enhanced efficiency of the developed electrode for water splitting can be related to the improved morphology of the nanorod structure, high ordered array architecture, hydrophilic feature, and high adhesion of NiO nanorod arrays on the NF substrate.

Exploring the synergistic effect of palladium-doped molybdenum phosphate as an electrode material for high-performance asymmetric supercapacitor device

In this research, we synthesized molybdenum phosphate (MoP) and palladium-doped MoP on a porous Ni-foam substrate using a one-step hydrothermal method for supercapacitor electrodes. Various techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy were employed to investigate the structural and morphological properties of the synthesized materials. The MoP and MoP-Pd samples exhibited hexagonal rod-like structures, which contributed to their porosity and high electrochemical activity. Electrochemical testing revealed that MoP demonstrated an areal capacitance of 3.8 F/cm² (0.60 mA/cm²). With the addition of Pd to MoP, the capacitance increased to 4.05 F/cm² (0.62 mAh/cm²) at a current density of 4 mA/cm² in a 2 M KOH electrolyte. The charge storage kinetics of both MoP and MoP-Pd indicated a dominant diffusion-controlled contribution, attributed to the Faradic redox process. The MoP-Pd electrode displayed excellent stability, retaining about 90.7% of its initial capacitance, and exhibited a coulombic efficiency of 100% over 15,000 cycles. Furthermore, we assembled an asymmetric device (ASD) using MoP-Pd as the positive electrode and activated carbon (AC) as the negative electrode. This ASD demonstrated an areal capacitance of 0.44 F/cm² (0.21 mAh/cm²), accompanied by an energy density of 0.178 mWh/cm2 and a power density of 1.28 mW/cm² within a potential window of 0–1.8 V, measured at an applied current of 3 mA. These results highlight the significant supercapacitive potential of MoP, further enhanced by the addition of Pd, suggesting its promising application as an electrode material in energy storage systems.

Rapid synthesis of nickel–iron-oxide (NiFeOx) solid-solution nano-rods thin films on nickel foam as advanced electrocatalyst for sustained water oxidation

The development of earth-rich, noble-metal-free, and highly electroactive catalysts to accelerate the oxygen evolution reaction (OER) is a formidable challenge for the establishment of water-splitting technologies. Here, a solid-solution nickel-iron oxide (NiFeOx) electrocatalyst is readily grown on a Ni-foam (NF) substrate by a rapid and economical aerosol-assisted chemical vapor deposition process. In particular, the NiFeOx thin film fabricated in 40 min acquires a distinctive nanorod structure and proves to be stable and efficient for OER in alkaline solutions. It is shown that the catalyst needs a low over-potential of 226 mV to reach the typical current density of 10 mA/cm2, and it can approach a remarkable current density level of 1000 mA/cm2 by taking a slightly higher over-potential of 139 mV. The small Tafel slope of 64 mv.dec−1 and splendid electrochemical stability of 40 h at high current densities outperform many known FeNi-based anodes as well as commercial IrO2 and RuO2. The unique structure of the thin film offers many electroactive sites and a high surface area in combination with an improved electrical conductivity of NF, which is believed to play an imperative role in the excellent activity of the catalyst. The cost-effective and simple strategy to fabricate NiFeOx nano-fibrous is very attractive for the development of electrocatalysts for water splitting.

Cu-Doped WS2/Ni3S2 Coral-Like Heterojunction Grown on Ni Foam as an Electrocatalyst for Alkaline Oxygen Evolution Reaction

Finding an efficient and stable non-noble-metal catalyst for oxygen evolution reaction (OER) in alkaline environments is of great significance for reducing the cost of the catalyst. In this work, we doped Cu to the surface of WS2/Ni3S2 coral-like heterojunction grown on Ni foam substrate by physical deposition, which can promote the transfer of interface charge. An excellent OER catalytic performance with an overpotential as low as 281 mV at a current density of 100 mA·cm−2 is reached. At the same time, the attenuation of the sample is not significant after the durability test for 20 h in a current density of 100 mA·cm−2. Theoretical calculations and experimental results show that the synergistic effect of interfacial charge redistribution through the Cu-doped WS2/Ni3S2 heterojunction accelerates the process of alkaline OER reaction. This study provides a novel idea for the synthesis of non-noble metal alkaline OER catalysts.

Integrated capture and solar-driven utilization of CO2 from flue gas and air

Integrated capture and solar-driven utilization of CO2 from flue gas and air

Catalytic Steam-Reforming of Glycerol over LDHs-Derived Ni-Al Nanosheet Array Catalysts for Stable Hydrogen Production

In the present work, LDHs–derived Ni–Al nanosheet arrays (NiAl/NA) were successfully synthesized via a one–step hydrothermal method, and applied in the steam-reforming of glycerol reaction for enhanced and stable hydrogen production. The physicochemical properties of catalysts were characterized using various techniques, including XRD, SEM–EDS, XPS, N2–physisorption, Raman, and TG–DTG. The results indicate that smooth and cross–linked Ni–Al mixed metal oxide nanosheets were orderly and perpendicularly grown on the Ni foam substrate. The SEM line scan characterization reveals the metal concentration gradient from the bottom to the top of nanosheet, which leads to distinctly optimized Ni valence states and an optimized binding strength to oxygen species. Owing to the improved reducibility and more exposed active sites afforded by its array structures, the NiAl/NA catalyst shows enhanced glycerol conversion (83.1%) and a higher H2 yield (85.4%), as well as longer stability (1000 min), compared to the traditional Ni–Al nanosheet powder. According to the characterization results of spent catalysts and to density functional theory (DFT) calculations, coke deposition is effectively suppressed via array construction, with only 1.25 wt.% of amorphous carbons formed on NiAl/NA catalyst via CO disproportionation.

Unravelling the mechanistic pathway of the Ni5P4/NiSe heterojunction for catalyzing the urea-rich water oxidation

Designing cost-effective and high-active urea oxidation reaction (UOR) catalysts through interface engineering is highly imperative for the hydrogen economy. Unfortunately, the majority of reported studies focus on empirical exploration and seldom elucidate the modulation principle of interface engineering on the electronic structure for optimizing the catalytic UOR activity, hindering the rational construction of high-performance catalysts. In response, the Ni5P4/NiSe nanoplates with abundant interfaces are experimentally fabricated on the macroporous Ni foam substrate. The density functional theory (DFT) predictions decipher accelerated charge transmission at the Ni5P4/NiSe interfacial area, accompanied by the formation of a moderate d-band center. Subsequently, the dehydrogenation dynamics of the Ni5P4/NiSe heterojunction is effectively improved during the stepwise UOR process. As expected, the elaborate Ni5P4/NiSe exhibits outstanding UOR activity under tough environments (6.0 M KOH with urine or 0.5 M urea), further corroborating its prospects as excellent UOR catalysts for industrial applications.

Self-supported amorphous phosphide catalytic electrodes for electrochemical hydrogen production coupling with methanol upgrading

Efficient catalytic electrodes for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) are pivotal for massive production of green hydrogen from water electrolysis, and the further replacement of kinetically sluggish OER by tailored elecrooxidation of certain organics is a promising way to co-produce hydrogen and value-added chemicals via a more energy-saving and safer manner. Herein, amorphous Ni-Co-Fe ternary phosphides (NixCoyFez-Ps) with different Ni:Co:Fe ratios electrodeposited onto Ni foam (NF) substrate were served as self-supported catalytic electrodes for alkaline HER and OER. The Ni4Co4Fe1-P electrode deposited in solution at Ni:Co:Fe ratio of 4:4:1 displayed low overpotential (61 mV at −20 mA cm−2) and acceptable durability for HER, while the Ni2Co2Fe1-P electrode fabricated in deposition solution at Ni:Co:Fe ratio of 2:2:1 showed good OER efficiency (overpotential of 275 mV at 20 mA cm−2) and robust durability, the further replacement of OER by anodic methanol oxidation reaction (MOR) enabled selective production of formate with 110 mV lower anodic potential at 20 mA cm−2. The HER-MOR co-electrolysis system based on Ni4Co4Fe1-P cathode and Ni2Co2Fe1-P anode could save 1.4 kWh of electric energy per cubic meter of H2 relative to mere water electrolysis. The current work offers a feasible approach to co-produce H2 and value-upgraded formate via an energy-saving manner by rational design of catalytic electrodes and construction of co-electrolysis system, and paves the way for cost-effective co-preparation of more value-added organics and green hydrogen via electrolysis.

Anodic glycerol oxidation to formate facilitating cathodic hydrogen evolution with earth-abundant metal oxide catalysts

Substituting sluggish oxygen evolution reaction (OER) with glycerol electrooxidation reaction (GER) to formate is a promising strategy for addressing glycerol overproduction and hydrogen production efficiency concurrently. However, the poor formate selectivity and the use of noble-metal catalysts hamper electrolysis applications of glycerol. Herein, we present a commercial nickel foam-supported nickel cobaltite (NiCo2O4/NF) synthesized via a facile hydrothermal/annealing combined process. The as-synthesized earth-abundant metal oxide composite enables anodic GER to formate, achieving not only as low as potential of 1.23 V (vs. reversible hydrogen electrode, RHE) to deliver 10 mA cm−2, but also a large catalytic current density of 152 mA cm−2 with an exceeding formate faradic efficiency (FE) of 97 % at 1.6 V (vs. RHE). Synergy effect induced by intermetallic interactions of hierarchical NiCo2O4 nanostructures rooted in Ni foam substrate facilitates anodic oxidation of glycerol and assists cathodic hydrogen production simultaneously. In particular, a two-electrode electrolyser NiCo2O4/NF || Ni foam requires a cell voltage of as low as 1.35 V to achieve 10 mA cm−2, which is 320 mV lower than that of the conventional overall water splitting systems.

Superior electronic/ionic transport dynamics of Zn-Co-OH/MnO2 heterointerface containing oxygen vacancies for pseudocapacitive storage

The superior electronic/ionic transport dynamics of electrode materials have been crucial to achieve appealing high performance for supercapacitors. Herein, a fascinating one-dimensional (1D) zinc cobalt hydroxide nanobelts/0D irregular manganese dioxide nanoparticles (M-ZCOH) have been vertically loaded into the 3D Ni foam (NF) substrate wrapped by nitrogen-doped graphene (NPG) (M-ZCOH/NPG/NF) for supercapacitors. The ingeniously designed M-ZCOH/NPG/NF composites feature powerful built-in electric field (BIEF) introduced by well-defined heterointerface with abundant oxygen vacancies defects. The formed electron accumulation triggering strong interfacial interaction verified by the differential charge density analysis may endow M-ZCOH/NPG/NF with the extra driving force to increase the diffusion/adsorption of electrolyte ions, thereby facilitating electron/ion transfer kinetics. Also, the qualitative negative shift of the d band center for M-ZCOH composites further evidences a lower electron/ion transfer barrier compared with the monomers. Obviously, the penetrating understanding of heterointerface on the improved properties is manifestly interpreted by combining theoretical and experimental analysis. Moreover, the ingenious strategy of engineering the heterointerfaces in unique heterostructure with rich defects may provide a new prospect for optimizing other advanced materials in sustainable energy storage systems.