Nickel Species Research Articles

Repsol to invest EUR 2.5 bn to ramp up renewable hydrogen capacity

Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12 %, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni-xCa/ATP (x=3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation (ci) and hydrothermal synthesis (hs) method and then tested in GSR. Characterization results of XRD, N2 adsorption-desorption, H2-TPR, HRTEM, XPS, and NH3/CO2-TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO2. This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaOx interface sites. Therefore, Ni-6Ca/ATP-hs exhibits the highest conversion (86.77%) of glycerol to gas product and H2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP-hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

BASF builds battery recycling prototype and pilot catalyst units

Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12 %, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni-xCa/ATP (x=3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation (ci) and hydrothermal synthesis (hs) method and then tested in GSR. Characterization results of XRD, N2 adsorption-desorption, H2-TPR, HRTEM, XPS, and NH3/CO2-TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO2. This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaOx interface sites. Therefore, Ni-6Ca/ATP-hs exhibits the highest conversion (86.77%) of glycerol to gas product and H2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP-hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

Evonik is building a new alkoxides plant in Southeast Asia

Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12 %, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni-xCa/ATP (x=3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation (ci) and hydrothermal synthesis (hs) method and then tested in GSR. Characterization results of XRD, N2 adsorption-desorption, H2-TPR, HRTEM, XPS, and NH3/CO2-TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO2. This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaOx interface sites. Therefore, Ni-6Ca/ATP-hs exhibits the highest conversion (86.77%) of glycerol to gas product and H2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP-hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

Atomic Disorder Enables Superior Catalytic Surface of Pt-Based Catalysts for Alkaline Hydrogen Evolution

Crystalline Pt catalyst for alkaline hydrogen evolution reaction (HER) catalysis is essentially hindered by the slow water dissociation kinetics, originated from the almost full-filled d orbitals and limited numbers of the coordination-unsaturated sites. Breaking the symmetrical atomic arrangements is theoretically feasible to solve this issue, but technically challenging. Herein, surface-disordered Pt–Ni nanowires (d-Pt–Ni NWs) are synthesized via a lithiation/delithiation method. The d-Pt–Ni NWs exhibit an ultralow overpotential of 15 mV at 10 mA cm–2 for HER catalysis, substantially superior to the crystalline counterpart and commercial Pt/C. Fine structural analyses reveal that the structural disorder can well regulate the electronic structures of Pt–Ni and the generated oxygenated nickel species contribute to stabilize the disordered structures. Furthermore, theoretical studies unravel that the oxygenated nickel with lower unoccupied orbitals helps facilitate water dissociation, while the upshift of the d band center of Pt enables superior H adsorption. More importantly, surface disordering is finally demonstrated to be a universal strategy to boost the HER activities of Pt-based alloys. Manipulating the surface atomic arrangement offers a new opportunity to design and optimize Pt-based catalysts and beyond.

Selective conversion of levulinic acid to gamma-valerolactone over Ni-based catalysts: Impacts of catalyst formulation on sintering of nickel

Selective production of γ-valerolactone (GVL) from hydrogenation of levulinic acid (LA) is challenging over non-noble metal catalysts but attractive due to the promising application of GVL as platform chemical. In this study, Ni catalysts supported on Mg-Al and Ni-Al layered double hydroxides (LDH) were synthesized for hydrogenation of LA. LDH as the precursor could create developed porous structure and facilitate dispersion of Ni species. These factors together achieved selective conversion of LA to GVL with maximum yield of 99% over the 2.25Ni-0.75Mg-Al catalyst. The Ni-based catalysts are not active for the ring-opening of GVL. Mg and Al together in 2.25Ni-0.75Mg-Al suppressed the sintering of nickel species in ethanol, achieving much superior reusability to Ni-Mg. However, in water, the transformation of MgO in either Ni-Mg or 2.25Ni-0.75Mg-Al to amorphous Mg(OH)2 led to the collapse of pore structure and remarkable deactivation of the catalysts, while Ni-Al without Mg species performed much better.

Divergent Aminocarbonylations of Alkynes Enabled by Photoredox/Nickel Dual Catalysis.

A metallaphotoredox-catalyzed strategy for the selective and divergent aminocarbonylation of alkynes with amines and 1 atm of CO is reported. This synergistic protocol not only enables the Markovnikov-selective hydroaminocarbonylation of alkynes to afford α,β-unsaturated amides, but also facilitates a sequential four-component hydroaminocarbonylation/radical alkylation in the presence of tertiary and secondary alkyl boronate esters, which allows for straightforward conversion of alkynes into corresponding amides. Preliminary mechanistic studies disclose that a photoinduced oxidative insertion of aniline and CO into nickel followed by a migratory insertion of (carbamoyl)nickel species could be involved.

Divergent Aminocarbonylations of Alkynes Enabled by Photoredox/Nickel Dual Catalysis

AbstractA metallaphotoredox‐catalyzed strategy for the selective and divergent aminocarbonylation of alkynes with amines and 1 atm of CO is reported. This synergistic protocol not only enables the Markovnikov‐selective hydroaminocarbonylation of alkynes to afford α,β‐unsaturated amides, but also facilitates a sequential four‐component hydroaminocarbonylation/radical alkylation in the presence of tertiary and secondary alkyl boronate esters, which allows for straightforward conversion of alkynes into corresponding amides. Preliminary mechanistic studies disclose that a photoinduced oxidative insertion of aniline and CO into nickel followed by a migratory insertion of (carbamoyl)nickel species could be involved.

Effect of Annealing on Surface Morphology and Structure of Nickel Coatings Deposited from Deep Eutectic Solvents

Nanocrystalline nickel coatings deposited on a copper base material from DES made of choline chloride and ethylene glycol in 1:2 molar ratio containing 1 mol dm−3 NiCl2⋅6H2O were modified through post-deposition heat treatment at the temperatures from 100 to 400 °C. As-deposited coatings were composed of spheroidal agglomerates with the size of several hundred nanometers interspersed with lamellar crystals, but after annealing at 300 °C and 400 °C only single nano-sized plates embedded in a granular and porous layer remained. As the temperature of the heat treatment increased from 100 °C to 400 °C, the mean crystallite size increased from 13 to 35 nm. The change in crystallite size was accompanied by a change in microhardness, the maximum value of which was measured for the annealed coating at 200 °C. As a result of heat treatment, coatings were gradually covered by a layer of oxidized nickel species. XPS analyses showed that NiOOH and Ni(OH)2 dominated among them. Above 200 °C the share of these compounds began to decline in the face of the increasing share of NiO. This, in turn, clearly translated into a deterioration of the corrosion resistance of Ni coatings annealed at 300 °C, and especially at 400 °C, during exposure in 0.05 mol dm−3 NaCl solution.

Consistent controls on trace metal micronutrient speciation in wetland soils and stream sediments

Trace metal are essential for microbially-mediated biogeochemical processes occurring in anoxic wetland soils and stream bed sediments, but low availability of these elements may inhibit anaerobic element cycling and transformations. Solid-phase speciation is likely a critical control on trace metal availability but has seen limited study in anoxic systems having concentrations similar to geological background levels, where metal limitations may be most prevalent. We have investigated trace metal concentrations and solid-phase speciation in three freshwater subsurface aquatic systems: marsh wetland soils, riparian wetland soils, and the sediments of a streambed. These systems displayed low solid-phase trace metal concentrations, generally at or below geological background levels, which generally followed the trend Zn > Cu ≈ Ni > Co and showed no correlation with major element compositions. All soils and sediments were dominated by quartz but varied in clay mineralogy as well as the organic matter, total sulfur, and total iron contents. X-ray absorption near-edge structure (XANES) spectroscopy shows that sulfur speciation in both wetlands is dominated by organic sulfur. Elemental sulfur and iron sulfides together made up <25% of the sulfur in the wetland soils, but the distribution between inorganic and organic forms was reversed in the stream sediments. Ferrous and ferric iron in clay minerals were common species identified by both XANES and extended X-ray absorption fine structure (EXAFS) spectroscopies at all sites. Iron(III) oxides were substantial components in all but the marsh wetland soils. Quantitative analysis of copper, nickel, and zinc XANES spectra revealed similar metal speciation across all sites. Copper speciation was dominated by sulfides, adsorbed species, and minor amounts of copper bound to organic matter; no metallic copper was detected. Nickel speciation also varied little and was dominated by nickel in clay mineral octahedral sheets and nickel sulfide, with adsorbed species also present. Zinc speciation was slightly more varied, with the marsh wetland soils and stream bed sediments containing adsorbed species, zinc associated with clay mineral structures, and zinc bound to reduced sulfur groups on organic matter, whereas the riparian wetland soils lacked clay-associated zinc but contained zinc sulfide. Trace metals bound to reduced sulfur occurred at every site, with a greater sulfur-bound fraction for copper. The fractional abundance of sulfur-bound species showed no relationship with soil or sediment total sulfur content, which varied by two orders of magnitude. More broadly, the observations in this study suggest that trace metal speciation in freshwater wetland soils and stream sediments is consistently dominated by a small set of recurring components which are distinct for each metal. This may represent a general geochemical phenomenon in anoxic soils and sediments containing trace metals at background concentrations (as low as 3 µg g−1) that was not predicted from systems that are contaminated with or naturally-enriched in copper, nickel, or zinc.

Effect of cobalt promotion on hydrotalcite-derived nickel catalyst for CO2 methanation

A series of cobalt-promoted Ni-Mg-Al hydrotalcite-derived catalysts were tested towards CO2 methanation reaction. The best among examined catalysts was the one with 1 wt% of cobalt in fresh hydrotalcite, obtaining 77% of CO2 conversion and 99% of CH4 selectivity at 300 °C. Above that temperature, the catalyst was working with-near-equilibrium parameters. It was also stable for up to 24 h on stream. Other cobalt-containing samples were likewise very active and selective during the time on stream. Due to the use of a low amount of cobalt (0.5–4 wt%) the Co-Ni alloy was not the subject of research – both materials formed probably solid solution of cobalt in the nickel matrix. Although the behavior of cobalt as a textural and electronic promoter was confirmed. Co was found to improve reducibility of nickel species, hydrogen uptake, and the acidic/basic properties by increasing the number of medium strength and strong basic sites. Tendency to sintering of nickel crystallites on cobalt-promoted catalysts was not confirmed in this study, however, with increased content of Co, bigger metal crystallites were formed under the reduction conditions.

Nano-Sized NiO Immobilized on Au/CNT for Benzyl Alcohol Oxidation: Influences of Hybrid Structure and Interface.

Tiny gold nanoparticles were successfully anchored on carbon nanotubes (CNT) with NiO decoration by a two-step synthesis. Characterizations suggested that Ni species in an oxidative state preferred to be highly dispersed on CNT. During the synthesis, in situ reduction by NaBH4 and thermal treatment in oxidation atmosphere were consequently carried out, causing the formation of Au-Ni-Ox interfaces and bimetal hybrid structure depending on the Ni/Au atomic ratios. With an appropriate Ni/Au atomic ratio of 8:1, Ni atoms migrated into the sub-layers of Au particles and induced the lattice contraction of Au particles, whilst a higher Ni/Au atomic ratio led to the accumulation of NiO fractions surrounding Au particles. Both contributed to the well-defined Au-Ni-Ox interface and accelerated reaction rates. Nickel species acted as structure promoters with essential Au-Ni-Ox hybrid structure as well as the active oxygen supplier, accounting for the enhanced activity for benzyl alcohol oxidation. However, the over-layer of unsaturated gold sites easily occured under a high Ni/Au ratio, resulting in a lower reaction rate. With an Au/Ni atomic ratio of 8:1, the specific rate of AuNi8/CNT reached 185 μmol/g/s at only 50 °C in O2 at ordinary pressure.

Steam reforming of n-hexane and toluene: Understanding impacts of structural difference of aliphatic and aromatic hydrocarbons on their coking behaviours

Plastic wastes are potential feedstock for the production of hydrogen via gasification. Aliphatic hydrocarbons and aromatic hydrocarbons are important fractions from pyrolysis of plastic wastes, which might show the different reaction behaviors in steam reforming reactions due to their distinct molecular structures. To explore this, in this study, steam reforming of n-hexane and toluene, two model compounds representing respective aliphatic hydrocarbons and aromatic hydrocarbons, over Ni/SBA-15 catalyst were carried out. The in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterization of the steam reforming indicated that the dissociative absorption of n-hexane on nickel took place even at 100 °C, form abundant CHx species and consequently more CH4 in gaseous products. Nevertheless, the reaction intermediates from n-hexane could be gasified by the OH from adsorbed water rapidly. In comparison, the fragments from dissociative adsorption of toluene reacted with hydroxyl group of water, forming the stable intermediates bearing OH, CO, COC and CC functionalities, which were the precursors of coke and resulted in more serious coking. The coke from steam reforming of toluene showed a higher thermal stability, higher resistivity to oxidation as it was more aromatic and contained more defective with big fused ring structures. In addition, the majority carbon nanotubes generated during steam reforming of toluene had an inner diameter of 3–6 nm and outer diameter of 10–20 nm. Nickel species on tip of the nanotubes were wrapped with a carbon layer, which contributed to the deactivation of the catalyst in steam reforming of toluene.

Nonsymmetrical Benzene–Pyridine-Based Nickel Pincer Complexes Featuring Borohydride, Formate, Ethyl, and Nitrosyl Ligands

Nonsymmetrical nickel PCN pincer complexes [Ni(iPrPCNX)Cl] (X = NMe, CH2) are obtained by metalation of the benzene–pyridine-based pincer ligand iPrPCNX (X = NMe, CH2) with [Ni(dme)Cl2] (dme = 1,2-dimethoxyethane). These nickel species afforded the respective borohydride and ethyl complexes [Ni(iPrPCNX)L] (L = BH4, Et) upon treatment with NaBH4 and EtMgBr (or Et2Mg), respectively. Reacting [Ni(iPrPCNX)(κ2-BH4)] with CO2 gave the formate complexes [Ni(iPrPCNX)(OCHO)]. Treatment of [Ni(iPrPCNX)Cl] with the nitrosyl salt NOBF4 led to the formation of the unusual cationic square-pyramidal nickel nitrosyl pincer complexes [Ni(iPrPCNX)(NO)Cl]+ featuring a strongly bent NO ligand (∠Ni–N–O 128.5°). These systems can be described as {NiNO}10 according to the Enemark–Feltham convention. Despite of the bent nature of the NO ligand the νNO is observed at 1849 cm–1 which is more typical for a linear Ni–N–O arrangement. The structure of these complexes is rationalized by means of DFT calculations. The molecular structures of representative complexes are presented.

Cerium decorated amorphous ternary Ni-Ce-B catalyst for enhanced electrocatalytic water oxidation

Metal borides have been acknowledged as promising candidates for alkaline oxygen evolution reaction (OER). Here, amorphous ternary metal borides (Ni-Ce-B) with different molar ratios of Ce% are achieved by a facile wet chemical method. With the optimal 5% of Ce, the as-prepared Ni-Ce-B-5/NF electrode exhibits comparable OER performance with lower overpotential (240 mV) than that of pure Ni-B/NF electrode (330 mV) and other metal borides. The high activity of Ni-Ce-B/NF is attributed to the amorphous structure and synergistic effect of binary metal Ni and Ce in Ni-Ce-B materials. Additionally, CeO2-x forms and serves as an electron acceptor during the self-electrooxidation process, facilitating the formation of crystalline high-valence nickel species, resulting in robust electrocatalysis and long-term stability. This work presents a Ce-based metal boride as a promising candidate for the low-cost and highly efficient OER catalyst.

Microsheets like nickel cobalt phosphate thin films as cathode for hybrid asymmetric solid-state supercapacitor: Influence of nickel and cobalt ratio variation

A rational combination of metal cations is necessary to obtain a synergistic effect leading to improved electrochemical energy storage performance of bimetal compounds. So, the effect of concentration variation of reactants (nickel and cobalt ratio) in nickel cobalt phosphate material and their influence on physicochemical properties and electrochemical capacitive performances are investigated. The morphological evolution from microflowers (nickel phosphate) to microsheets (cobalt phosphate) is observed with increasing cobalt content in nickel cobalt phosphate thin films. The optimum nickel and cobalt composition (∼1:1) in nickel cobalt phosphate (Ni1.38Co1.62(PO4)2·8H2O) thin film electrode demonstrate maximum specific capacitance (capacity) of 1116 F g−1 (446 C g−1) at 0.5 A g−1 current density. Also, a fabricated hybrid asymmetric aqueous device consists of nickel cobalt phosphate thin film as cathode and rGO as an anode in 1 M KOH electrolyte delivers a higher specific capacitance of 120 F g−1 with a high energy density of 42.3 Wh kg−1 at a power density of 1 kW kg−1. Moreover, a hybrid asymmetric solid-state device fabricated using PVA-KOH gel electrolyte exhibits a maximum specific capacitance of 102 F g−1 with an energy density of 36.2 Wh kg−1 at 160 W kg−1 power density and 83.7 % initial capacitance retention after 4000 GCD cycles. Such excellent electrochemical capacitive performance of hybrid asymmetric devices is attributed to the synergy between nickel and cobalt species in nickel cobalt phosphate thin film electrodes, suggesting its potential application as a cathode in hybrid energy storage devices.

Experimental Electrochemical Potentials of Nickel Complexes

AbstractNickel-catalyzed cross-coupling and photoredox catalytic reactions has found widespread utilities in organic synthesis. Redox processes are key intermediate steps in many catalytic cycles. As a result, it is pertinent to measure and document the redox potentials of various nickel species as precatalysts, catalysts, and intermediates. The redox potentials of a transition-metal complex are governed by its oxidation state, ligand, and the solvent environment. This article tabulates experimentally measured redox potentials of nickel complexes supported on common ligands under various conditions. This review article serves as a versatile tool to help synthetic organic and organometallic chemists evaluate the feasibility and kinetics of redox events occurring at the nickel center, when designing catalytic reactions and preparing nickel complexes.1 Introduction1.1 Scope1.2 Measurement of Formal Redox Potentials1.3 Redox Potentials in Nonaqueous Solution2 Redox Potentials of Nickel Complexes2.1 Redox Potentials of (Phosphine)Ni Complexes2.2 Redox Potentials of (Nitrogen)Ni Complexes2.3 Redox Potentials of (NHC)Ni Complexes

Monovalent Nickel-Mediated Radical Formation: A Concerted Halogen-Atom Dissociation Pathway Determined by Electroanalytical Studies.

The recent success of nickel catalysts in stereoconvergent cross-coupling and cross-electrophile coupling reactions partly stems from the ability of monovalent nickel species to activate C(sp3) electrophiles and generate radical intermediates. This electroanalytical study of the commonly applied (bpy)Ni catalyst elucidates the mechanism of this critical step. Data rule out outer-sphere electron transfer and two-electron oxidative addition pathways. The linear free energy relationship between rates and the bond-dissociation free energies, the electronic and steric effects of the nickel complexes and the electrophiles, and DFT calculations support a variant of the halogen-atom abstraction pathway, the inner-sphere electron transfer concerted with halogen-atom dissociation. This mechanism accounts for the observed reactivity of different electrophiles in cross-coupling reactions and provides a mechanistic rationale for the chemoselectivity obtained in cross-electrophile coupling over homocoupling.

Atomically dispersed nickel species in a two-dimensional molecular sieve: Origin of high activity and stability in dry reforming of methane

Two-dimensional (2D) molecular sieves with highly dispersed nickel species are attractive catalysts for the dry reforming of methane (DRM) because of the ease of molecular diffusion and the deactivation resistance by coke deposition. Here we report the single-step preparation of a 2D nickel silicate molecular sieve with delaminated MWW layers (Ni-DML) by the simple hydrothermal conversion of a borosilicate MWW precursor with nickel nitrate solution. More than 20 wt.% of nickel species were well dispersed in the framework of Ni-DML and the lowest stabilization energy of nickel cluster was calculated using density functional theory calculations. Ni-DML exhibited extremely high conversions of CH4 and CO2 as well as an extraordinary stability, maintaining its activity for 10 days on stream due to the in-situ formation of metallic nickel clusters from the framework species. Ni-DML can be used as a catalyst for DRM without pretreatments such as air calcination and H2 reduction.

The Formation of Polyethylene Using α‐Diiminonickel Precatalyst in the Presence of CoCp2 and AgOTf

AbstractThe controllable preparation of polyolefin products has always been the goal pursued by researchers, while the structure of polyolefin will have a greater impact on the performance and application of the material. Here, we used a redox active nickel catalyst to modulate the properties of polyethylene through multiple control of reaction conditions. Reductant CoCp2 and oxidant AgOTf were used to induce the valence change of the nickel species and then affected the ethylene polymerization performance. Chain structure, molecular weight, melting point and other properties of polyethylene were investigated to evaluate the catalytic performance. Besides, the characterization indicated that the addition of reductant into the catalytic system might help to change the state of the nickel active center.

Distribution and size fractionation of nickel and cobalt species along the Amazon estuary and mixing plume

The Amazon River has the largest drainage basin in the world, making it a major source of trace elements and dissolved organic matter (DOM) to the Atlantic Ocean. However, despite the increasing anthropogenic impacts to the Amazon basin, few recent studies exist quantifying trace element data in this region. The aim of the study was to analyze the input and removal processes that influence the transport of Ni and Co species in the Amazon and Pará River estuaries and mixing zone. Toward this goal, this work provides a comprehensive mixing and speciation study for the trace elements Ni and Co. Samples were collected during a period of high river discharge on the RV Meteor cruise M147 (Amazon – GEOTRACES process study GApr11) in the Amazon and Pará River outflow regions, as well as the aging mixing plume to the north, a mangrove belt to the southeast and the North Brazil Current (NBC) seawater endmember. Here we present the results for labile particulate (>0.2 μm), labile and total dissolved (<0.2 μm), large colloidal (0.015–0.2 μm), soluble (<0.015 μm) and ultrafiltered (<1 and < 10 kDa) fractions of Ni and Co in surface waters (towed-fish) and along the water column at different depths (CTD) using comparative approaches by adsorptive cathodic stripping voltammetry (AdCSV) and inductively coupled plasma-mass spectrometry (ICP-MS). We observed good agreement between AdCSV and ICP-MS measurements for Ni, and to a lesser extent Co. In general, dissolved and soluble Ni and Co decreased with increasing salinity, however additional non-conservative removal was also observed and attributed to possible biological uptake and colloidal flocculation. Shipboard AdCSV measurements showed that dissolved Ni was present mostly in the “reactive” form as weak complexes, suggesting high bioavailability, while reactive dissolved Co was absent, indicating the presence of strong organic Co complexes. In both Ni and Co, an elevated colloidal fraction was observed at low salinity, suggesting removal of dissolved Ni and Co via colloidal flocculation upon seawater mixing, while the soluble species were transported to the Atlantic Ocean. At depth, the soluble phase dominated, and we observed concentration maxima at 500–1000 m, indicating the presence of Antarctic Intermediate Water (AIW) and possible biological regeneration. We also observed unique source signatures in dissolved and labile particulate Ni and Co species from the Amazon and Pará River outflow regions, in addition to a contribution from mangrove belt-associated groundwater.