Interfacial coupling in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>CsSnCl</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:mo>−</mml:mo> <mml:msub> <mml:mi>MoS</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mro

The electrochemical instability of Sn-based halide perovskites in aqueous media is commonly linked to surface electron accumulation and defect-assisted oxidation of ${\mathrm{Sn}}^{2+}$ to ${\mathrm{Sn}}^{4+}$. Here, we examine how interfacial coupling in a cesium tin chloride (${\mathrm{CsSnCl}}_{3})$-molybdenum disulfide $({\mathrm{MoS}}_{2})$ (CSC--MS, 10%) composite electrode influences charge distribution and electrochemical behavior. Electrochemical and spectroscopic measurements indicate trends consistent with effective electronic redistribution at the interface between $n$-type ${\mathrm{CsSnCl}}_{3}$ and $p$-type 2H-${\mathrm{MoS}}_{2}$, suggestive of a type-II--like alignment. Mott-Schottky analysis yields an apparent flat-band offset on the order of several hundred millivolts, which reflects an effective interfacial capacitance response rather than a uniquely defined junction potential in the heterogeneous composite electrode. Correlated trends in x-ray photoelectron spectroscopy, impedance spectroscopy, and kinetic analyses support reduced near-surface electron density in ${\mathrm{CsSnCl}}_{3}$ and an enhanced pseudocapacitive response. In addition, ${\mathrm{MoS}}_{2}$ contributes hydrophobic basal planes and electronically active edge states that cooperatively improve interfacial stability, electronic percolation, and charge transport. As a result, the composite exhibits a kinetically extended aqueous operating window approaching 2.3 V under scan conditions and mixed charge-storage behavior in which reversible ${\mathrm{Sn}}^{2+}/{\mathrm{Sn}}^{4+}$ redox processes are contributory but not exclusive. These results provide a physically consistent, though not uniquely resolved, picture of how interfacial coupling and composite engineering can enhance the aqueous pseudocapacitive performance of lead-free halide perovskite electrodes.