Enhanced Oxygen Evolution Reaction Performance on NiS<i>_x</i>@Co₃O₄/Nickel Foam Electrocatalysts with Their Photothermal Property

Based on the principle of heterogeneous catalysis for water electrolysis, electrocatalysts with appropriate electronic structure and photothermal property are expected to drive the oxygen evolution reaction effectively. Herein, amorphous NiSx-coupled nanourchin-like Co3O4 was prepared on nickel foam (NiSx@Co3O4/NF) and investigated as a electrocatalyst for photothermal-assisted oxygen evolution reaction. The experimental investigations and simulant calculations jointly revealed NiSx@Co3O4/NF to be of suitable electronic structure and high near-infrared photothermal conversion capability to achieve the oxygen evolution reaction advantageously both in thermodynamics and in kinetics. Relative to Co3O4/NF and NiSx/NF, better oxygen evolution reaction activity, kinetics, and stability were achieved on NiSx@Co3O4/NF in 1.0 M KOH owing to the NiSx/Co3O4 synergetic effect. In addition, the oxygen evolution reaction performance of NiSx@Co3O4/NF can be obviously enhanced under near-infrared light irradiation, since NiSx@Co3O4 can absorb the near-infrared light to produce electric and thermal field. For the photothermal-mediated oxygen evolution reaction, the overpotential and Tafel slope of NiSx@Co3O4/NF at 50 mA cm–2 were reduced by 23 mV and 13 mV/dec, respectively. The present work provides an inspiring reference to design and develop photothermal-assisted water electrolysis using abundant solar energy

First-Principles Calculations on Narrow-Band Gap d¹⁰ Metal Oxides for Photocatalytic H₂ Production: Role of Unusual In²⁺ Cations in Band Engineering

The d10 metal oxides with low effective mass and high mobility of photoexcited electrons have received much attention in photocatalytic water splitting. However, there are still challenges in practical application due to insufficient visible light absorption. Here, an unusual phenomenon of the In2+ cation in PtIn6(GeO4)2O and PtIn6(Ga/InO4)2 with a narrow band gap is systematically investigated using density functional theory calculations. According to chemical bond analysis, the final band edge structure results from the interaction between the empty In-5p orbitals and the occupied antibonding state of the In 5s–O 2p orbitals as well as the further hybridization of adjacent In cations in PtIn6 octahedrons. The unique bonding characteristic of In2+ cations endows them with a narrow band gap and visible light response ability. Moreover, the occupied antibonding state could weaken the strength of the In–O covalent bond and strengthen the orbital hybridization of the In–In bond, causing the conduction band minimum to be located in the electroactive In6 cavity. This work reveals the origin of the narrow band gap of PtIn6(GeO4)2O and PtIn6(Ga/InO4)2 in view of bond theory and shows that they are promising semiconductors for the application of photocatalytic H2 generation

Enhanced Oxygen Evolution Reaction Performance on NiS<i>_x</i>@Co₃O₄/Nickel Foam Electrocatalysts with Their Photothermal Property

Based on the principle of heterogeneous catalysis for water electrolysis, electrocatalysts with appropriate electronic structure and photothermal property are expected to drive the oxygen evolution reaction effectively. Herein, amorphous NiSx-coupled nanourchin-like Co3O4 was prepared on nickel foam (NiSx@Co3O4/NF) and investigated as a electrocatalyst for photothermal-assisted oxygen evolution reaction. The experimental investigations and simulant calculations jointly revealed NiSx@Co3O4/NF to be of suitable electronic structure and high near-infrared photothermal conversion capability to achieve the oxygen evolution reaction advantageously both in thermodynamics and in kinetics. Relative to Co3O4/NF and NiSx/NF, better oxygen evolution reaction activity, kinetics, and stability were achieved on NiSx@Co3O4/NF in 1.0 M KOH owing to the NiSx/Co3O4 synergetic effect. In addition, the oxygen evolution reaction performance of NiSx@Co3O4/NF can be obviously enhanced under near-infrared light irradiation, since NiSx@Co3O4 can absorb the near-infrared light to produce electric and thermal field. For the photothermal-mediated oxygen evolution reaction, the overpotential and Tafel slope of NiSx@Co3O4/NF at 50 mA cm–2 were reduced by 23 mV and 13 mV/dec, respectively. The present work provides an inspiring reference to design and develop photothermal-assisted water electrolysis using abundant solar energy

Performance Evolution of Typical Electrocatalysts with Electrolyte Temperature during Alkaline Water Electrolysis

From Arrhenius and Eyring equations, it can be known that the temperature of an electrolyte has a significant influence on the performance of electrocatalysts during water electrolysis, but this factor is usually ignored in fundamental research. Herein, the activity, kinetics, and stability of some typical electrocatalysts (Co3O4, NiFe alloy, NiFe LDH, and Pt) for oxygen and hydrogen evolution reactions in the KOH electrolyte at different temperatures (20∼80 °C) were investigated. Relative to the lower-temperature KOH electrolyte, the electrocatalysts in higher-temperature electrolytes showed a better water electrolysis activity and kinetics, which can be attributed to the higher conductivity at the electrolyte/electrode interface, stronger hydrophilicity on electrocatalysts, more active site formation, and lower water electrolysis resistance on electrocatalysts, but they had weaker reaction stability. In the KOH electrolyte at a higher temperature, the weaker stability of electrocatalysts mainly originated from their stronger dissolution during water electrolysis

Performance Evolution of Typical Electrocatalysts with Electrolyte Temperature during Alkaline Water Electrolysis

From Arrhenius and Eyring equations, it can be known that the temperature of an electrolyte has a significant influence on the performance of electrocatalysts during water electrolysis, but this factor is usually ignored in fundamental research. Herein, the activity, kinetics, and stability of some typical electrocatalysts (Co3O4, NiFe alloy, NiFe LDH, and Pt) for oxygen and hydrogen evolution reactions in the KOH electrolyte at different temperatures (20∼80 °C) were investigated. Relative to the lower-temperature KOH electrolyte, the electrocatalysts in higher-temperature electrolytes showed a better water electrolysis activity and kinetics, which can be attributed to the higher conductivity at the electrolyte/electrode interface, stronger hydrophilicity on electrocatalysts, more active site formation, and lower water electrolysis resistance on electrocatalysts, but they had weaker reaction stability. In the KOH electrolyte at a higher temperature, the weaker stability of electrocatalysts mainly originated from their stronger dissolution during water electrolysis

Performance Evolution of Typical Electrocatalysts with Electrolyte Temperature during Alkaline Water Electrolysis

From Arrhenius and Eyring equations, it can be known that the temperature of an electrolyte has a significant influence on the performance of electrocatalysts during water electrolysis, but this factor is usually ignored in fundamental research. Herein, the activity, kinetics, and stability of some typical electrocatalysts (Co3O4, NiFe alloy, NiFe LDH, and Pt) for oxygen and hydrogen evolution reactions in the KOH electrolyte at different temperatures (20∼80 °C) were investigated. Relative to the lower-temperature KOH electrolyte, the electrocatalysts in higher-temperature electrolytes showed a better water electrolysis activity and kinetics, which can be attributed to the higher conductivity at the electrolyte/electrode interface, stronger hydrophilicity on electrocatalysts, more active site formation, and lower water electrolysis resistance on electrocatalysts, but they had weaker reaction stability. In the KOH electrolyte at a higher temperature, the weaker stability of electrocatalysts mainly originated from their stronger dissolution during water electrolysis