Bismuth activated succulent-like binary metal sulfide heterostructure as a binder-free electrocatalyst for enhanced oxygen evolution reaction

The facile synthesis of and light-driven water splitting on a hetero-metallic bismuth oxide catalyst

The process of water photo-electrolysis possesses the capability to generate sustainable and renewable hydrogen fuels, consequently addressing the challenge of the irregularity of solar energy. Thus, developing highly-efficient and low-cost electrocatalysts for the use in contemporary renewable energy devices is critical. Herein, we report the fabrication of a novel BaCeFex-yBixO6 nanocrystalline material through a one-step solvothermal route using a post-annealing process at 500 °C. The synthesized material was investigated for its light-induced electrochemical HER and OER activities in alkaline media and the results revealed that the as-prepared BaCeFex-yBixO6-500 °C exhibited an excellent OER activity with an overpotential of 100 mV to achieve a current density of 10 mA cm-2, thus outperforming the IrO2 electrocatalyst. Besides its excellent water oxidation performance, the catalyst also demonstrated an admirable HER activity comparable to that of the Pt/C catalyst, indicating that the higher temperature treatment plays a significant role in achieving the maximum performance of the developed electrocatalyst. This work provides insights into the enhancement of light-induced OER and HER activities of bismuth oxides for a wide range of catalytic applications.

Phytochemical-assisted green synthesis of CuFeOx nano-rose electrocatalysts for oxygen evolution reaction in alkaline media

This study represents a green synthesis method for fabricating an oxygen evolution reaction (OER) electrode by depositing two-dimensional CuFeO_x on nickel foam (NF). Two-dimensional CuFeO_x was deposited on NF using in situ hydrothermal synthesis in the presence of Aloe vera extract. This phytochemical-assisted synthesis of CuFeO_x resulted in a unique nano-rose-like morphology (petal diameter 30-70 nm), which significantly improved the electrochemical surface area of the electrode. The synthesized electrode was analyzed for its OER electrocatalytic activity and it was observed that using 75% Aloe vera extract in the phytochemical-assisted synthesis of CuFeO_x resulted in improved OER electrocatalytic performance by attaining an overpotential of 310 mV for 50 mA cm^-2 and 410 mV for 100 mA cm^-2. The electrode also sustained robust stability throughout the 50 h of chronopotentiometry studies under alkaline electrolyte conditions, demonstrating its potential as an efficient OER electrode material. This study highlights the promising use of Aloe vera extract as a green and cost-effective way to synthesize efficient OER electrode materials.

Bismuth-Based Multi-Component Heterostructured Nanocatalysts for Hydrogen Generation

Developing a unique catalytic system with enhanced activity is the topmost priority in the science of H2 energy to reduce costs in large-scale applications, such as automobiles and domestic sectors. Researchers are striving to design an effective catalytic system capable of significantly accelerating H2 production efficiency through green pathways, such as photochemical, electrochemical, and photoelectrochemical routes. Bi-based nanocatalysts are relatively cost-effective and environmentally benign materials which possess advanced optoelectronic properties. However, these nanocatalysts suffer back recombination reactions during photochemical and photoelectrochemical operations which impede their catalytic efficiency. However, heterojunction formation allows the separation of electron–hole pairs to avoid recombination via interfacial charge transfer. Thus, synergetic effects between the Bi-based heterostructured nanocatalysts largely improves the course of H2 generation. Here, we propose the systematic review of Bi-based heterostructured nanocatalysts, highlighting an in-depth discussion of various exceptional heterostructures, such as TiO2/BiWO6, BiWO6/Bi2S3, Bi2WO6/BiVO4, Bi2O3/Bi2WO6, ZnIn2S4/BiVO4, Bi2O3/Bi2MoO6, etc. The reviewed heterostructures exhibit excellent H2 evolution efficiency, ascribed to their higher stability, more exposed active sites, controlled morphology, and remarkable band-gap tunability. We adopted a slightly different approach for reviewing Bi-based heterostructures, compiling them according to their applicability in H2 energy and discussing challenges, prospects, and guidance to develop better and more efficient nanocatalytic systems.

A comprehensive review on the electrochemical parameters and recent material development of electrochemical water splitting electrocatalysts

Electrochemical splitting of water is an appealing solution for energy storage and conversion to overcome the reliance on depleting fossil fuel reserves and prevent severe deterioration of the global climate. Though there are several fuel cells, hydrogen (H2) and oxygen (O2) fuel cells have zero carbon emissions, and water is the only by-product. Countless researchers worldwide are working on the fundamentals, i.e. the parameters affecting the electrocatalysis of water splitting and electrocatalysts that could improve the performance of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) and overall simplify the water electrolysis process. Noble metals like platinum for HER and ruthenium and iridium for OER were used earlier; however, being expensive, there are more feasible options than employing these metals for all commercialization. The review discusses the recent developments in metal and metalloid HER and OER electrocatalysts from the s, p and d block elements. The evaluation perspectives for electrocatalysts of electrochemical water splitting are also highlighted.

Local Photothermal Effect Enabling Ni3 Bi2 S2 Nanoarray Efficient Water Electrolysis at Large Current Density

In terms of the large-scale hydrogen production by water electrolysis, achieving the bifunctional electrocatalyst with high efficiency and stability at high current densities is of great significance but still remains a grand challenge. To address this issue, herein, one unique hybrid electrode is synthesized with the local photothermal effect (LPTE) by supporting the novel ternary nickel (Ni)bismuth (Bi)sulfur (S) nanosheet arrays onto nickel foam (Ni₃ Bi₂ S₂ @NF) via a one-pot hydrothermal reaction. The combined experimental and theoretical observations reveal that owing to the intrinsic LPTE action of Bi, robust phase stability of Ni₃ Bi₂ S₂ as well as the synergistic effect with hierarchical configuration, upon injecting the light, the as-prepared Ni₃ Bi₂ S₂ exhibits remarkably improved efficiency of 44% and 35% for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Such enhanced values are also comparable to those performed in working media heated to 80 °C. In addition, the overall water splitting system by using Ni₃ Bi₂ S₂ @NF as bifunctional electrodes only delivers an ultralow voltage of 1.40 V at 10 mA cm^-2 under LPTE, and can be stable more than 36 h at 500-1000 mA cm^-2 . More broadly, even worked at 0-5 °C, alkaline simulated seawater and high salt seawater, the electrodes still show apparent LPTE effect for improving catalytic efficiency.

Nickel sulfide nanorods decorated on graphene as advanced hydrogen evolution electrocatalysts in acidic and alkaline media

Nowadays, the fabrication of robust and earth-abundant hydrogen evolution electrocatalysts with noble-metal-like catalytic activities is still facing great challenges. In this report, nanorod (NR)-shaped nickel sulfide (NiS) is successfully decorated on graphene (Gr) by utilizing carbon cloth (CC) as a substrate (NiS-Gr-CC). Benefiting from the NR morphology and strong interfacial synergetic effect between NiS and Gr, the NiS-Gr-CC electrocatalyst shows good catalytic activity for hydrogen evolution reaction (HER). Specifically, the low Tafel slopes of 46 and 56 mV dec^-1 along with the small overpotentials of 66 and 71 mV at 10 mA cm^-2 are obtained in the acidic and alkaline electrolytes, respectively. Density functional theory results indicate that the combination of NiS and Gr can optimize the adsorption energy of H* during the HER process. The long-term durability measurement result reveals that our NiS-Gr-CC heterostructure has good electrocatalytic cycling stability (∼80 h) in both acidic and alkaline electrolytes. These results confirm that the NiS-Gr-CC heterostructure is a promising candidate for hydrogen evolution electrocatalyst with high catalytic activity.

Incorporation of Bi2O3 Residuals with Metallic Bi as High Performance Electrocatalyst toward Hydrogen Evolution Reaction

Nanostructured Bismuth-based materials are promising electrodes for highly efficient electrochemical reduction processes such as hydrogen evolution reaction (HER). In this work, a novel sort of nanocomposite made up of partially reduced Bi2O3 into metallic Bi anchored on a 3D network of Ni-foam as a high-performance catalyst for electrochemical hydrogen reduction. The application of the hybrid material for HER is shown. The high catalytic activity of the fabricated electrocatalyst arises from the co-operative effect of Bi/Bi2O3 and Ni-foam which provides a highly effective surface area combined with the highly porous structure of Ni-foam for efficient charge and mass transport. The advantages of the electrode for the electrochemical reduction processes such as high current density, low overpotential, and high stability of the electrode are revealed. An overall comparison of our as-prepared electrocatalyst with recently reported works on related work is done.

Three-dimensional core-shell heterostructure of tungsten trioxide/bismuth molybdate/cobalt phosphate for enhanced photoelectrochemical water splitting

Hydrogen has attracted increasing attention as clean energy for fuel cells over the past decade. Photoelectrochemical (PEC) water splitting is considered the most feasible production method but its practical efficiency depends significantly on the photogeneration rate of electron (e^-) and hole (h⁺) on a semiconductor photoanode and the rapid separation of these charge carriers. A proper match of small and large bandgap positions is also necessary. This paper presents a three-dimensional core-shell heterostructured tungsten trioxide/bismuth molybdate/cobalt phosphate (WO₃/Bi₂MoO₆/Co-Pi) photocatalyst synthesized using simultaneous hydrothermal and electrodeposition techniques. Uniform Bi₂MoO₆ nanoflakes formed on WO₃ nanoplates as evidenced by various micro-spectroscopic techniques. The as-prepared WO₃/Bi₂MoO₆/Co-Pi hetero-photocatalyst exhibited significantly high photoelectrochemical activity, where its photocurrent efficiency was 4.6 times greater than that of the constituent WO_3. Such drastic improvement in the PEC properties can be corroborated by the appropriate bandgap alignment among WO₃, Bi₂MoO₆, and Co-Pi, resulting in a sufficient charge carrier density with efficient, fast charge-transport complementing their structural-morphological synergy. Furthermore, a heterojunction charge-transfer mechanism was proposed to verify the role of the co-catalyst, Co-Pi, in enhancing the photocurrent at the WO₃/Bi₂MoO₆ photoanode under the same applied bias.

Evaluation of synergistic effect from Ag-AgCl1/3Br1/3I1/3 composite on photocatalytic degradation the oil field pollutants

A series of Ag/AgX (X = Cl, Br, I; X = Cl, Br, or X = Cl, I, or X = Br, I; X = Cl, Br, and I) composite photocatalysts were synthesized via a facile photoreduction. The several characterization methods of X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS) mapping and X-ray photoelectron spectroscopy (XPS) were characterized the samples. Through evaluation the photocatalytic activity of degradation rhodamine, methyl orange, and phenol, Ag-AgCl_1/3Br_1/3I_1/3 exhibited the superior selective photocatalytic activities than other photocatalysts. The reason for improved photocatalytic property of Ag-AgCl_1/3Br_1/3I_1/3 was attributed to the multifarious halogen atoms with the synergistic effect and the surface plasmon resonance (SPR) effect of Ag⁰. Furthermore, the recycle experiments were conducted to reveal the stability and reusability, the trapping experiments confirmed the active species of Ag-AgCl_1/3Br_1/3I_1/3.