Structural design of Janus lamellar membrane based on bismuth oxychloride for comprehensive solar energy utilization

Photocatalysis and photothermal water evaporation (PWE), as two technologies that utilize solar energy, have received special attention in the context of carbon neutrality. It is undoubtedly attractive if a structure can effectively combine the two technologies. However, it remains a huge challenge to simplify structural design while improving energy efficiency and mass transfer. Herein, a Janus lamellar membrane (JLM) with an asymmetric bi-layered structure was constructed using facile vacuum filtration. Specifically, the top layer consists of BiOCl nanosheets (BNs) and cellulose nanofibers@carbon nanotubes (CNF@CNT), forming a functional layer that facilitates solar energy utilization. Within the top and bottom layers, CNF@CNT and CNFs are respectively embedded into the interlayer space formed by stacked BNs, offering abundant nanochannels for continuous and rapid water supply. Moreover, as the weight ratio of the BN-CNF@CNT and BN-CNF precursors is optimized to 1:1 with the BN-CNF@CNT layer facing light source, the photocatalytic hydrogen evolution (PHE) rate of JLM reaches up to 39.81 μmol·g−1·h−1, corresponding to approximately 3.12 and 1.57 times that of the BN-CNF and BN-CNF@CNT lamellar membranes, respectively. Importantly, the PHE rate remains consistent within ten cyclic stability experiments. Furthermore, the PWE rate of JLM achieves 1.98 kg·m−2·h−1 under 1.0 solar irradiation (100 mW·cm−2). A vital advantage of the JLM is its ability to float on the liquid surface, enabling concurrent photocatalytic decontamination and PWE processes. The research on designing JLM with an asymmetric structure for both photocatalysis and PWE provides a practical approach to the comprehensive utilization of solar energy.