Built-in Electric Fields Enhancing Photocarrier Separation and H2 Evolution

The construct of the internal electric field (IEF) is recognized as an effective driver for promoting charge migration and separation to enhance photocatalytic performance. In this study, one-dimensional nanorods of Mn_0.2Cd_0.8S (MCS) co-doped with interstitial chlorine (Cl_int) and substitutional chlorine (Cl_sub) were designed and synthesized using a one-step solvothermal method. The incorporation of Cl_int and Cl_sub led to an unbalanced charge distribution and the formation of IEF in the MCS nanorods, contributing to the improvement of photogenerated carrier kinetic behavior. Through density functional theory (DFT) calculations, the effect of Cl_int and Cl_sub doping on the activity of the MCS was visually explained by examining differences in electronic structure, charge distribution and H₂ adsorption/desorption balance. Interestingly, the modulation of the energy band structure of MCS primarily resulted from the contribution of Cl_int, while Cl_sub playing a negligible role. Moreover, the Cl_sub further facilitated the optimization of Cl_int concerning the H₂ adsorption-desorption Gibbs free energy $\left(\Delta G_{\text{H}*}\right)$ of MCS. Ultimately, the $\Delta G_{\text{H}*}$ of 0.9 Cl-MCS favored H₂ production (1.14 vs. 0.17 eV), leading to a 9 times increase in photocatalytic H₂ production activity compared to MCS. This investigation presents a valuable approach for constructing IEF in bimetallic sulfide photocatalysts.

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