Photocatalytic hydrogen (H2) evolution via water spilling over semiconductors has been considered to be one of the most promising strategies for sustainable energy supply in the future to provide ...non-pollution and renewable energy. The key to efficient conversion of solar-chemical energy is the design of an efficient structure for high charge separation and transportation. Therefore, cocatalysts are necessary in boosting photocatalytic H2 evolution. To date, semiconductor photocatalysts have been modified by various cocatalysts due to the extended light harvest, enhanced charge carrier separation efficiency and improved stability. This review focuses on recent developments of cocatalysts in photocatalytic H2 evolution, the roles and mechanism of the cocatalysts are discussed in detail. The cocatalysts can be divided into the following categories: metal/alloy cocatalysts, metal phosphides cocatalysts, metal oxide/hydroxide cocatalysts, carbon-based cocatalysts, dual cocatalysts, Z-scheme cocatalysts and MOFs cocatalysts. The future research and forecast for photocatalytic hydrogen generation are also suggested.
The roles and mechanism of cocatalysts, extended light harvest, enhanced charge carrier separation efficiency and improved stability are summarized to offer a conceptual basis for designing and developing highly efficient photocatalytic H2-evolution cocatalysts.
Co-substituted LaFeO3 was electrodeposited on the surface of BiVO4 as a co-catalyst to enhance the water splitting performance. Compared to bare BiVO4, the BiVO4/Co-LaFeO3 composite photoanode shows ...a water oxidation photocurrent of 3.4 mA/cm2 at 1.23 V versus reverse hydrogen electrode, accompanied by a notable cathodic shift in the onset potential for 300 mV. Combined optical and electrochemical characterizations show that the solid/electrolyte charge transfer efficiency of BiVO4 are dramatically improved by the incorporation of Co-substituted LaFeO3. From the surface kinetic study of charge carriers by intensity-modulated photocurrent spectroscopy, a suppressed surface recombination rate constant is observed and the enhanced photoelectrochemical water splitting performance observed in the BiVO4/Co-LaFeO3 photoanode is attributed to the surface passivation effect of Co-substituted LaFeO3.
Rational design and building of high efficiency, secure and inexpensive electrocatalyst is a pressing demand and performance to promote sustainable improvement of hydrogen energy. The bifunctional ...electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution response (HER) with high catalytic performance and steadiness in the equal electrolyte are extra treasured and meaningful. Herein, a unique three-dimensional (3D) structure electrocatalyst for NiCo2S4 growing on the flower-like NiFeP was designed and synthesized in this study. The results show that the flower-like NiCo2S4/NiFeP/NF composite electrocatalyst has large specific surface area, appropriate electrical conductivity, and greater lively websites uncovered in the three-dimensional structure, and affords extraordinary electrocatalytic overall performance for the ordinary water splitting. In alkaline solution, the OER and HER overpotentials of NiCo2S4/NiFeP/NF only need 293 mV and 205 mV overpotential to provide the current densities of 100 mA/cm2 and 50 mA/cm2, respectively. This high electrocatalytic activity exceeds the catalytic activity of most nickel-iron based electrocatalysts for OER and HER process. Accordingly, the optimized NiCo2S4/NiFeP/NF sample has higher stability (24 h) at 1.560 and 10 mA/cm2, which extensively speeds up the overall water splitting process. In view of the above performance, this work offers a fine approach for the further improvement of low fee and excessive effectivity electrocatalyst.
A facile strategy is developed to synthesize three-dimensional flower-like NiCo2S4/NiFeP/NF bifunctional electrocatalyst. Using commercially available solar cells (about 2 V) for NiCo2S4/NiFeP/NF||NiCo2S4/NiFeP/NF cell power supply, and the continuous evolution of H2 and O2 bubbles in the two electrodes. Display omitted
Highly transparent and UV-resistant superhydrophobic arrays of SiO2-coated ZnO nanorods are prepared in a sequence of low-temperature (<150 °C) steps on both glass and thin sheets of PET (2 × 2 ...in.2), and the superhydrophobic nanocomposite is shown to have minimal impact on solar cell device performance under AM1.5G illumination. Flexible plastics can serve as front cell and backing materials in the manufacture of flexible displays and solar cells.
Fe2TiO5 was synthesized via the solvothermal method and adopted as co-catalyst to improve the photoelectrochemical (PEC) water splitting performance of BiVO4 photoanode. After surface modification by ...Fe2TiO5, the BiVO4/Fe2TiO5 photoanode shows a 300 mV cathodic shift in onset potential and 3 times enhancement in photocurrent, which delivers a photocurrent density of 3.2 mA/cm2 at 1.23 V vs reverse hydrogen electrode. Systematic optical, electrochemical, and intensity-modulated photocurrent spectroscopy characterizations were performed to explore the role of Fe2TiO5 and reveal that the enhanced PEC performance is mainly caused by the surface passivation effect of Fe2TiO5.
The photocatalytic removal of nitric oxide (NO) is a promising technology used to reduce the level of harmful gaseous pollutants in parts per billion (ppb). As a potential photocatalyst, Bi2Sn2O7 has ...a low quantum efficiency due to its fast recombination rate of photo-generated carriers. In this paper, Bi/Bi2Sn2O7 was prepared by the in situ deposition of Bi. The structural, electrical, and optical properties of the attained sample were investigated through a series of analyses. The results demonstrate that Bi nanoparticles not only enhance the photoabsorption ability of Bi2Sn2O7 due to their surface plasmon resonance (SPR) effect, but also improve its photocatalytic activity. Photocatalytic performance was evaluated by the oxidation of NO at ppb level under xenon lamp (λ > 400 nm) irradiation. It was found that the photocatalytic NO removal rate increased from 7.2% (Bi2Sn2O7) to 38.6% (Bi/Bi2Sn2O7). The loading of Bi promotes the separation and migration of photo-generated carriers and enhances the generation of •O2− and •OH radicals responsible for the oxidation of NO. The Bi/Bi2Sn2O7 composite photocatalyst also exhibits excellent photocatalytic stability, which makes it a potential candidate for use in air purification systems.
The oxygen evolution reaction (OER) is a critical electrochemical reaction in water splitting and rechargeable metal-air batteries. It plays a pivotal role in achieving high-efficiency clean-energy ...production and energy storage in these devices. Transition metal-based bimetallic MOFs (TMB MOFs) with two different metal ions possess specific synergistic effects, which could exhibit OER performance and stability superior to those of the corresponding monometallic MOFs for water oxidation. Benefiting from the diversity of chemical composition and structural type, TMB MOFs can also serve as precursors and templates to obtain alloy-particle-decorated carbon materials with high surface area, or metal compounds such as bimetallic sulfides, phosphides, and hydroxides with atomic-level mixing of heterometallic elements. These materials with high-density active sites exhibit much improved catalytic activity in the water oxidation reaction. This article aims to review the recent progress with TMB MOFs and their derivatives in relation to applications as electrocatalysts in OER, including analysis of the mechanism of the OER process with the assistance of DFT calculations and
in situ
or
operando
techniques.
The review summarizes transition metal-based bimetallic MOFs and their derived materials as electrocatalytic materials for the OER. The mechanisms of the OER as probed by DFT calculation and
in situ
characterization techniques are also discussed.
The bare surface of BiVO4 photoanode usually suffers from extremely low interfacial charge transfer efficiency which leads to a significantly suppressed photoelectrochemical water splitting ...performance. Various strategies, including surface modification and the loading of co-catalysts, facilitate the interface charge transfer process in BiVO4. In this study, we demonstrate that CoS2 synthesized from the hydrothermal method can be used as a high-efficient co-catalyst to sufficiently improve the interface charge transfer efficiency in BiVO4. The photoelectrochemical water splitting performance of BiVO4 was significantly improved after CoS2 surface modification. The BiVO4/CoS2 photoanode achieved an excellent photocurrent density of 5.2 mA/cm2 at 1.23 V versus RHE under AM 1.5 G illumination, corresponding to a 3.7 times enhancement in photocurrent compared with bare BiVO4. The onset potential of the BiVO4/CoS2 photoanode was also negatively shifted by 210 mV. The followed systematic combined optical and electrochemical characterization results reveal that the interfacial charge transfer efficiency of BiVO4 was largely improved from less than 20% to more than 70% due tor CoS2 surface modification. The further surface carrier dynamics study performed using an intensity modulated photocurrent spectroscopy displayed a 6–10 times suppression in surface recombination rate constants for CoS2 modified BiVO4, which suggests that the key reason for the improved interfacial charge transfer efficiency possibly originates from the passivated surface states due to the coating of CoS2.
A facile strategy is developed to synthesize NiFe-LDH-Vo@NiCu electrocatalysts with high efficient electrocatalytic performance, and vacancy construction/NiCu alloy effects stimulate the electrons ...more localized around Ni.
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•A facile strategy is developed to synthesize NiFe-LDH-Vo@NiCu bifunctional electrocatalyst.•NiFe-LDH-Vo@NiCu electrode exhibits excellent electrocatalytic activity and low cell voltage.•Vacancy construction and NiCu alloy effects stimulate the electrons more localized around Ni.
Designing bifunctional electrocatalytic materials with non-precious metals for efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains a tremendous challenge. NiFe layered double-hydroxide (NiFe-LDH) materialss with modifiable nanostructures and tunable electronic properties have attracted considerable attention. At present, its modification strategies mainly include single structural defect, simple material composite and so on, while there are few studies involving multiple structure defect synergy. In this work, environmental-friendly hydrothermal-electrodeposition method was employed to build oxygen defects on the surface of NiFe layered double hydroxides and anchor NiCu nanoclusters with abundant, cheap nickel foam (NF) as the conductive substrate. The synergistic effect of oxygen defects and NiCu alloys resulted in a significant increase in the exposure of active sites and an enjoyable enhancement in intrinsic electrocatalytic activity. The obtained NiFe-LDH-Vo@NiCu sample exhibits outstanding OER (244 mV@50 mA cm−2)/HER (85 mV@10 mA cm−2) performance in 1 M KOH solution. Furthermore, NiFe-LDH-Vo@NiCu presents ultra-low battery voltage of 1.54 V as well as remarkable stability as a bifunctional electrode. Finally, DFT calculations were applied to reveal the effects of the introduction of O vacancies and the anchoring of NiCu nanoclusters on the internal electronic structure of NiFe-LDH materials. In general, this research can provide new insights into designing of high performance NiFe-LDH electrocatalysts.
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