Abstract
Co-catalysis is regarded as a promising strategy to improve the hydrogen evolution performance of semiconductor-based photocatalysts. But developing a simple and effective technique to achieve the optimal synergy between co-catalysts and host photocatalysts has been a great challenge. Herein, hybrid photocatalysts consisting of β-NiS modified CdS nanowires (NiS/CdS NWs) have been synthesized via a simple and green hydrothermal route using CdS NWs as the template from thiourea and nickel acetate in the presence of sodium hypophosphite. As a result, a metal Ni intermediate was formed via an electroless plating process assisted by H2PO2-, which facilitated the growth of highly conducting flake-like β-NiS nanostructures onto the surface of the CdS NWs. With the optimal loading amount of NiS, the obtained NiS/CdS NWs present a record-high photocatalytic activity for H2 evolution in lactic acid aqueous solutions under visible light irradiation. At 25 °C, the rate of H2 evolution was measured as 793.6 μmol h-1 (over a 5 mg photocatalyst sample), which is nearly 250-fold higher than that over pure CdS NWs, and the apparent quantum yield reached an exceptionally high value of 74.1% at 420 nm. The mechanism for the photocatalytic H2 evolution over the present NiS/CdS NWs was also proposed. This strategy would provide new insight into the design and development of high-performance heterostructured photocatalysts.
Highlights
To alleviate the ever-increasing consumption of fossil fuels and the associated environmental pollution as well as global climate change, considerable efforts have recently been devoted to developing clean, abundant, and renewable energy as an alternative to fossil fuels
To synthesize the proposed nickel sul de (NiS)/cadmium sul de (CdS) NW hybrid photocatalyst, 29 mg ($0.2 mmol) of CdS NWs and a designated amount of Ni(CH3COO)2$4H2O were dispersed in 50 mL of deionized water, and stirred for 3 h
Increasing the loading amount of NiS onto CdS through increasing the Ni/Cd feed molar ratio (FMR) rst led to an increase and a decrease in the H2 evolution rate, with the highest H2 evolution reaction (HER) rate of 592.1 mmol hÀ1 achieved by the NiS/CdS hybrid photocatalyst prepared at a Ni/Cd FMR of 0.8, which is ca. 204-fold higher than that of pure CdS NWs
Summary
In the last decade, cadmium sul de (CdS) has received considerable attention for use as an efficient HER photocatalyst due to its suitable direct band-gap ($2.5 eV) allowing for the absorption of visible light of the solar spectrum, as well as its appropriate conduction band (CB) and valence band (VB) positions, which are thermodynamically favorable for water splitting.[10]. Onedimensional (1D) nanostructures (e.g. nanowires and nanotubes) offer several advantages, for example, a large surface area resulting from their high aspect ratios, high charge separation and transfer efficiencies, and enhanced light absorption ability, which could substantially improve the activity of the photocatalytic HER.[3,36,37] the challenge lies in obtaining good contact between the CdS semiconductor host photocatalysts and co-catalysts over the entire 1D structure to enhance the transfer efficiency of photo-generated carriers To address these problems, we develop a simple and green hydrothermal synthesis route to fabricate a b-NiS modi ed CdS nanowire (NiS/CdS NW) hybrid photocatalyst using CdS NWs as the scaffold. This simple, cost-effective, and environmentally friendly strategy would provide new insight into the design and development of high-performance heterostructured photocatalysts
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