Enhancing photo electrocatalytic water splitting efficiency using Bi2O2CO3@Ni(OH)2 composite with flower-like morphology

Abstract

The rational design of semiconductor heterojunctions is pivotal in enhancing photoelectrochemical (PEC) water-splitting performance. In this study, we synthesized Bi₂O₂CO₃ (BOC) nanosheets, Ni(OH)₂ (NH) nanosheets, and their composite Bi₂O₂CO₃@Ni(OH)₂ (BOC-NH) separately using a hydrothermal process. The BOC-NH composite displays a distinct 3D flower-like structure with cross-linked petals of 21.82 nm, substantially enhancing the surface area and facilitating effective heterojunction formation between BOC and NH. This synergistic effect enhances charge separation and transport, leading to superior PEC water oxidation performance. The BOC-NH photoanode achieved a remarkable photocurrent density of 5.87 mA/cm², 4.48 times higher than pure BOC and 1.75 times that of NH, along with a reduced onset potential of 0.464 V. Transient photocurrent measurements demonstrated excellent stability, while electrochemical impedance spectroscopy (EIS) revealed a significantly lower solution resistance (11.06 Ω), and charge transfer resistance (5.27 Ω) compared to the individual BOC and NH photoanodes. The applied bias photon-to-current efficiency (ABPE) of BOC, NH, and BOC-NH was 0.21 %, 0.36 %, and 0.58 %, respectively, with the composite showing the highest efficiency under light illumination. Long-term stability tests over 7200 s showed sustained photoactivity, with the photocurrent density rising from 0.26 to 0.53 mA/cm², highlighting the durability of the composite. This work presents a robust strategy for improving PEC water splitting through heterojunction engineering and morphological optimization.