pH-dependent electrochemical interface reconstruction: A facile route to BiOCl/bi₂₄O₃₁cl₁₀ heterojunction with boosted conductivity and cycling stability for supercapacitors

BiOCl and its derivatives show considerable promise for supercapacitor applications because of their high theoretical specific capacity and rich redox activity. However, their practical performance is often limited by poor electrical conductivity and structural instability. To address these issues, we constructed a BiOCl/Bi₂₄O₃₁Cl₁₀ heterojunction to improve both charge transport and structural stability. A flake-like BiOCl precursor was first synthesized and then electrochemically treated at a constant current of 0.02 A over a wide pH range (1−13) to generate a BiOCl/Bi₂₄O₃₁Cl₁₀ heterojunction, denoted as BiOCl-1/24-X. By tuning the pH of the reaction system, pH-dependent formation of a reconstructed Bi₂₄O₃₁Cl₁₀ phase on the BiOCl surface was achieved, thereby strengthening the interfacial interaction between the two phases. This interfacial reconstruction process modulated the extent of heterointerface formation and the concentration of oxygen-vacancy-related defects, thereby promoting ion transport and charge-transfer kinetics. The results indicate that the sample treated at pH = 9 exhibits battery-type energy-storage behavior dominated by diffusion-controlled processes. Accordingly, it delivered a specific capacity of 411C·g−1 at 1·A g−1, far exceeding that of pristine BiOCl (80C·g−1). Moreover, it retained 79.3% of its initial capacity after 10,000 cycles. It also achieved an energy density of 35.67 Wh·kg−1 at a power density of 923.83 W·kg−1. In a practical demonstration, the BiOCl-1/24//AC device powered a 3.2 V LED for 900 s, highlighting its application potential. This work proposes a facile electrochemical interfacial reconstruction strategy for developing high-performance electrode materials, offering a simpler and more effective alternative to conventional chemical methods.