CoPi/Co(OH)₂ Modified Ta₃N₅ as New Photocatalyst for Photoelectrochemical Cathodic Protection of 304 Stainless Steel

In this work, CoPi and Co(OH)₂ nanoparticles were deposited on the surface of Ta₃N₅ nanorod-arrays to yield a novel broad-spectrum response photocatalytic material for 304 stainless steel photocatalytic cathodic protection. The Ta₃N₅ nanorod-arrays were prepared by vapor-phase hydrothermal (VPH) and nitriding processes and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy, respectively, to obtain morphologies, crystal structures, surface compositions, and light response range. In order to analyze the performance improvement mechanism of CoPi/Co(OH)₂ on Ta₃N₅ nanorod-arrays, the electrochemical behavior of modified and unmodified Ta₃N₅ was obtained by measuring the open circuit potential and photocurrent in 3.5 wt% NaCl solution. The results revealed that the modified Ta₃N₅ material better protects 304 stainless steel at protection potentials reaching −0.45 V.

Hybrids of iridium–cobalt phosphates as a highly efficient electrocatalyst for the oxygen evolution reaction in neutral solution

Iridium–cobalt phosphates act as highly efficient electrocatalysts for water oxidation with an intrinsic activity even superior to iridium phosphate.

Electrodeposited Amorphous Tungsten-doped Cobalt Oxide as an Efficient Catalyst for the Oxygen Evolution Reaction

Thin film of amorphous tungsten-doped cobalt oxide (W:CoO) was successfully grown on a conducting electrode via an electrochemical oxidation process employing a [Co(WS₄ )₂ ]^2- deposition bath. The W:CoO catalyst displays an attractive performance for the oxygen evolution reaction in an alkaline solution. In an NaOH solution of pH 13, W:CoO operates with a moderate onset overpotential of 230 mV and requires 320 mV overpotential to generate a catalytic current density of 10 mA cm^-2 . A low Tafel slope of 45 mV decade^-1 was determined, indicating a rapid O₂ -evolving kinetics. The as-prepared W:CoO belongs to the best cobalt oxide-based catalysts ever reported for the oxygen evolution (OER) reaction.

Electrodeposited Nickel-Cobalt-Sulfide Catalyst for the Hydrogen Evolution Reaction

A novel Ni-Co-S-based material prepared by the potentiodynamic deposition from an aqueous solution containing Ni²⁺, Co²⁺, and thiourea is studied as an electrocatalyst for the hydrogen evolution reaction (HER) in a neutral phosphate solution. The composition of the catalyst and the HER activity are tuned by varying the ratio of the concentrations of Ni²⁺ and Co²⁺ ions in the electrolytes. Under optimized deposition conditions, the bimetallic Ni-Co-S exhibits higher electrocatalytic activity than its monometallic counterparts. The Ni-Co-S catalyst requires an overpotential of 150 mV for the HER onset, and 10 mA cm^-2 current density is obtained at 280 mV overpotential. The catalyst exhibits two different Tafel slopes (93 and 70 mV dec^-1) indicating two dissimilar mechanisms. It is proposed that the catalyst comprises two types of catalytic active sites, and they contribute selectively toward HER in different potential regions.

In situ electrochemical surface derivation of cobalt phosphate from a Co(CO3)0.5(OH)·0.11H2O nanoarray for efficient water oxidation in neutral aqueous solution

In this Communication, cobalt phosphate (Co-Pi) has been successfully developed on a Co(CO₃)_0.5(OH)·0.11H₂O nanoarray (CCH NA) on Ti mesh in neutral phosphate-buffered solution (PBS) via in situ electrochemical surface derivation. The resulting core@shell structured CCH@Co-Pi NA/Ti exhibits remarkable activity toward water oxidation with the need of an overpotential of 460 mV to achieve a geometrical catalytic current density of 10 mA cm^-2 in 0.1 M PBS, with a high turnover frequency of and long-term electrochemical stability.

Ir-phosphate cocatalyst for photoelectrochemical water oxidation using α-Fe2O3

Ir-phosphate (Ir-Pi) cocatalyst on the surface of Fe₂O₃ acts as a redox shuttle and thus, reduces charge carrier recombination during PEC water oxidation reaction.

Electrochemical deposition of manganese oxide–phosphate–reduced graphene oxide composite and electrocatalysis of the oxygen evolution reaction

The MnO_x–Pi–rGO OER catalyst is prepared by the simultaneous electrochemical reduction of MnO₄⁻ ions and GO in a neutral phosphate electrolyte.

Magnesium cobalt silicate as a bifunctional catalyst for the O2 electrode and its application in Li–O2 cells

MgCoSiO₄ is synthesized by using mixed solvothermal approach and studied for oxygen evolution (OER) and reduction (ORR) reactions. It is also studied for non-aqueous Li–O₂ cells.

High Catalytic Activity of Amorphous Ir-Pi for Oxygen Evolution Reaction

Large-scale production of hydrogen gas by water electrolysis is hindered by the sluggish kinetics of oxygen evolution reaction (OER) at the anode. The development of a highly active and stable catalyst for OER is a challenging task. Electrochemically prepared amorphous metal-based catalysts have gained wide attention after the recent discovery of a cobalt-phosphate (Co-Pi) catalyst. Herein, an amorphous iridium-phosphate (Ir-Pi) is investigated as an oxygen evolution catalyst. The catalyst is prepared by the anodic polarization of carbon paper electrodes in neutral phosphate buffer solutions containing IrCl3. The Ir-Pi film deposited on the substrate has significant amounts of phosphate and Ir centers in an oxidation state higher than +4. Phosphate plays a significant role in the deposition of the catalyst and also in its activity toward OER. The onset potential of OER on the Ir-Pi is about 150 mV lower in comparison with the Co-Pi under identical experimental conditions. Thus, Ir-Pi is a promising catalyst for electrochemical oxidation of water.

Cobalt-embedded nitrogen doped carbon nanotubes: a bifunctional catalyst for oxygen electrode reactions in a wide pH range

Electrocatalysts for the oxygen reduction and evolution reactions (ORR/OER) are often functionally separated, meaning that they are only proficient at one of the tasks. Here we report a high-performance bifunctional catalyst for both ORR and OER in both alkaline and neutral media, which is made of cobalt-embedded nitrogen doped carbon nanotubes. In OER, it shows an overpotential of 200 mV in 0.1 M KOH and 300 mV in neutral media, while the current density reaches 50 mA cm(-2) in alkaline media and 10 mA cm(-2) in neutral media at overpotential of 300 mV. In ORR, it is on par with Pt/C in both alkaline and neutral media in terms of overpotential, but its stability is superior. Further study demonstrated that the high performance can be attributed to the coordination of N to Co and the concomitant structural defects arising from the transformation of cobalt-phthalocyanine precursor.