New 2D bismuth oxychalcogenide nanosheets have excellent theoretical properties such as high electronic mobility and excellent oxidation resistance, which have good application prospective for optoelectronic devices. In this paper, during the synthesis process via mild hydrothermal route, ammonium bismuth citrate (C6H13BiN2O7·H2O) is selected as Bi source. Both Bi2O2S and Bi2O2Se nanosheets (lateral size: over 2.0 µm, thickness: ≈ 5.0 nm) are synthesized successfully using thiourea (CH4N2S) as S source, and sodium selenite (Na2O3Se) as Se source, respectively. The as‐synthesized Bi2O2S and Bi2O2Se materials have desirable nanosheet‐like morphologies. After adding C6H13BiN2O7·H2O, [(NH3)2C6H7O7]3‐ can intercalate between the interlayers of Bi2O2S or Bi2O2Se, limiting the growth along c‐axis direction, so that 2D sheets can be obtained. Finally, the photodetectors are fabricated based on Bi2O2S and Bi2O2Se films coated by thermal spraying. The experimental results show that the maximum responsivity and detectivity of Bi2O2S‐based photodetector are 0.059 A W‐1 and 6.77 × 109 Jones, respectively. As to Bi2O2Se‐based photodetector, the maximum responsivity and detectivity can reach 75.14 A W‐1 and 3.95 × 1012 Jones, respectively. The mild hydrothermal synthesis using ammonium bismuth citrate as Bi source is a universal and facile method to obtain Bi2O2S and Bi2O2Se nanosheets for optoelectronic applications.

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Aqueous alkaline battery represents a promising energy storage technology with both high energy density and high power density as rechargeable batteries. However, the low theoretical capacities, kinetics and stability of anode materials have limited their developments and commercializations. In this study, we propose a novel method to produce two‐dimensional layered bismuth oxide selenium (Bi2O2Se) and reduced graphene oxide (rGO) composites via a one‐step hydrothermal method. The volume change caused by phase change during rapid charging and discharging is significantly reduced and the capacity reaches 263.83 mAh g−1 at a current density of 0.5 A g−1. The Bi2O2Se/rGO electrode exhibits excellent cycling stability in which the capacity retention rate is 81.04% after 5000 cycles. More importantly, the Bi2O2Se/rGO nanosheet composite is used as the anode electrode material with MnCo2O4.5@Ni(OH)2 as the cathode electrode material in aqueous alkaline battery. When the energy density is 76.16 W h kg−1, the power density reaches 308.65 W kg−1. At a power density of 10.21 kW kg−1, the energy density remains as high as 33.86 W h kg−1. The results presented here may advance the understanding of the issues facing the development of aqueous battery anode materials.

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