Interfacial engineering to boost photocatalytic hydrogen evolution via synergistic Z-scheme heterojunction in novel n-type metal free NiCoV-LDH/g-C3N4 composite

Abstract

Fabrication of low cost, highly effective, noble metal free, thermally and chemically stable photocatalyst and alkaline water electrocatalyst with the wide pH range is posing a significant challenge in the hydrogen evolution reaction from water splitting to resolve the worldwide energy issues. In this study we have designed a novel n-type 2D semiconductor NiCoV-LDH/g-C₃N₄ (LCN) composite with easy one-step hydrothermal method. Morphological results proved that in situ NiCoV-LDH lamellar sheets were deposited uniformly on g-C₃N₄ support, resulting in larger electrochemical active surface area and enhanced photo/electrocatalytic hydrogen evolution rate (HER). Furthermore, the LCN with 15 % loading of g-C₃N₄ (LCN-15) composite exhibited the highest photocatalytic hydrogen evolution rate of 1673.4 ${\mu \text{mol}g}^{-1}$, representing a 27.93-fold enhancement compared to that of bare CN at 59.9 ${\mu \text{mol}g}^{-1}\text{.}$ The improved photocatalytic activity of LCN-15 composite was attributed to (1) enhanced surface area with a large number of active sites, (2) slow formation of NiCoV-LDH precipitates leading to the fabrication of successful composite material with the g-C₃N₄, and (3) development of Z-scheme heterojunction, which effectively reduced the recombination rate of photogenerated charge carriers. Furthermore, the electrocatalytic HER performance for LCN-15 composite achieved a current density of −135.86 ${\text{mA}\text{cm}}^{-2}$, which was about 10 times greater than that for bare CN. Moreover, LCN-15 composite exhibited excellent stability during repeated usage for both photocatalytic activities. Thus, this study presented a successful development of NiCoV-LDH/g-C₃N₄ (LCN) composite structures for enhanced photo/electrocatalytic hydrogen evolution.