Designing In₂S₃/FeVO₄/CNT Photoelectrode for Enhanced Visible Light Driven Oxygen Evolution

The development of efficient and stable photoelectrodes is essential for the advancement of photoelectrochemical (PEC) water-splitting technologies, which hold promise for efficient oxygen evolution reaction (OER), necessary for sustainable hydrogen production. In this study, the synthesis of a ternary composite, In <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>2</mml:mn></mml:msub> <mml:annotation>${_2 }$</mml:annotation> </mml:semantics> </mml:math> S <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>3</mml:mn></mml:msub> <mml:annotation>${_3 }$</mml:annotation> </mml:semantics> </mml:math> /FeVO <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>4</mml:mn></mml:msub> <mml:annotation>${_4 }$</mml:annotation> </mml:semantics> </mml:math> /CNT has been reported, designed for highly efficient PEC oxygen evolution. The formation of In <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>2</mml:mn></mml:msub> <mml:annotation>${_2 }$</mml:annotation> </mml:semantics> </mml:math> S <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>3</mml:mn></mml:msub> <mml:annotation>${_3 }$</mml:annotation> </mml:semantics> </mml:math> /FeVO <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>4</mml:mn></mml:msub> <mml:annotation>${_4 }$</mml:annotation> </mml:semantics> </mml:math> heterostructure enhances PEC performance significantly due to the type-II band alignment, which minimizes electron-hole recombination and improves charge separation. The addition of CNTs further enhances performance by providing conductive pathways that improve electron transport and reduce charge transfer resistance. The resulting In <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>2</mml:mn></mml:msub> <mml:annotation>${_2 }$</mml:annotation> </mml:semantics> </mml:math> S <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>3</mml:mn></mml:msub> <mml:annotation>${_3 }$</mml:annotation> </mml:semantics> </mml:math> /FeVO <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mn>4</mml:mn></mml:msub> <mml:annotation>${_4 }$</mml:annotation> </mml:semantics> </mml:math> /CNT ternary composite achieves a current density of 14.70 mAcm <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msup><mml:mrow></mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>2</mml:mn></mml:mrow> </mml:msup> <mml:annotation>${^{ - 2} }$</mml:annotation> </mml:semantics> </mml:math> at 1.8 V vs. RHE, representing a notable increase in performance. Electrochemical impedance spectroscopy (EIS) shows that the ternary composite has the lowest charge transfer resistance, while Bode phase analysis indicates a longer carrier lifetime, emphasizing the synergistic effect of heterostructure formation and CNT inclusion. The ternary composite also demonstrates excellent stability and responsiveness during transient photocurrent cycling, maintaining performance under repeated chronoamperometric ON/OFF cycles, making it a strong candidate for water-splitting applications driven by visible light.