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Designing nanoscale photocatalysts to improve photocatalytic efficiency is a popular research topic. However, for wide application and friendly environment, achieving good dispersion and multiple recycling of photocatalysts at the nanoscale remains challenging. Herein, a general bottom-up assembly method is proposed for designing a class of two-dimensional lamellar membranes (2DLMs) for photocatalytic applications. A bismuth oxychloride (BiOCl) nanosheet (BN) was used as a demo photocatalyst to construct a 2DLM via self-stacking. The designed BiOCl membrane (BM) exhibited excellent physical properties including flexibility, mechanical strength (tensile strength = 15.75 MPa, fracture strain = 0.056%), and translucence, as well as superior photocatalytic performance with excellent recycling stability and reusability. The photocatalytic hydrogen evolution performance of BM was 2.5-fold that of BN particles dispersed in an aqueous solution. Further theoretical calculations revealed that a BM with appropriately sized nanochannels can accelerate water transport, and the main horizontal channel size of the BM (3.13 nm) is very close to the size of the ideal water transport nanochannel. Furthermore, the confined internal space reduces the number of hydrogen bonds for water molecules within the nanochannels, thereby enhancing the interfacial reaction rate and photocatalytic efficiency. This study presents a simple bottom-up assembly method to design photocatalysts with further improved performance. [Display omitted] • A general strategy to design lamellar membrane (LM) for photocatalytic is proposed. • The nanochannels speed up water transport and facilitate photocatalytic reaction. • The hydrogen bonds among water molecules inside nanochannels are weakened. • Photocatalytic H 2 evolution activity of BiOCl LM is 2.5-fold that of its particles. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D BiOCl lamellar membrane with CNFs is constructed for photocatalyst. • Hydrogen evolution rate of BiOCl/CNF 2DLM is 4.7-times that of the BiOCl nanosheets. • Experimental and theoretical analyses revealed the effect of CNFs on photocatalysis. • CNFs can regulate hydrogen bonds networks of confined water. • Confined water promotes the release of H+ from H 2 O. Photocatalytic hydrogen evolution (PHE) is a sustainable alternative for generating green and clean energy. However, it requires the use of nanoscale photocatalysts, whose applicability is limited by their poor reusability and proton release from water molecules. Herein, a porous two-dimensional lamellar membrane (2DLM) photocatalyst was fabricated from bismuth oxychloride (BiOCl) nanosheets (BNs) and cellulose nanofibers (CNFs) via layer-by-layer self-assembly. The hybridization of the CNFs with the BNs improved the PHE rate of the resulting BiOCl/CNFs membrane (BCM). The optimal PHE rate was observed for a CNF content of 3.2 wt% and was 4.7-times that of raw BNs dispersed in an aqueous solution alone and 1.85-times that of the BiOCl membrane (BM). Moreover, the PHE rate remained unchanged even after 10 discontinuous cycles for a total time of 60 h. Comprehensive experimental characterization and molecular dynamics simulations confirmed that the introduction of the CNFs effectively regulated the hydrogen bond network of the confined water molecules, thus improving the efficiency of the conversion of H 2 O into H 2. Meanwhile, the optimization of the nanochannel sizes of the BNs by the hybridized CNFs accelerated water transport within the nanochannels. The 2DLM also showed excellent mechanical strength, flexibility, and translucence. This strategy of fabricating 2DLMs using a nanosheet photocatalyst and CNFs not only results in improved PHE performance but also should also aid the development of stable and reusable photocatalysts for other industrial applications. [ABSTRACT FROM AUTHOR]