Electrochemical water splitting is a promising strategy for reducing hydrogen production costs. However, the conventional phosphate buffer (PBS) electrolyte incurs a huge energy penalty in high overpotential ranges. This study investigates the hydrogen evolution reaction (HER) performance using two buffer electrolytes with different charge properties: H₂ PO₄^–/HPO₄^2– (PBS pK_a = 6.90) and IMZH⁺/IMZ (IMZS pK_a = 7.03). On Pt microelectrodes, results reveal that the plateau current density of PBS correlates closely with the electrode potential, a trend not observed with IMZS. In addition, when using commercial Pt/C nanocatalysts loaded on carbon paper, the plateau current density phenomenon disappears in the IMZS electrolyte, which is attributed to the preconcentration effect of the positively charged hydrogen source. In situ Raman characterization indicates that the configuration of H₂ PO₄^– at the electrochemical interface changes as the electrode potential becomes progressively negative. In comparison, the adsorption configuration of IMZH⁺ remains considerably stable across the tested potential range. The grand canonical density functional theory method with both implicit and explicit solvation models was further used to investigate the influence of electrode potential on the dissociation of a differently charged hydrogen source. Results indicate that when the electrode potential becomes progressively negative, H₂ PO₄^– is repelled from the electrode surface owing to electrostatic forces, increasing Gibbs free energy of dissociation accordingly. This phenomenon contributes to the inevitable energy penalty observed in the PBS electrolyte for the HER. In comparison, the Gibbs free energy of dissociation of IMZH⁺ decreases monotonically with the progressive negative cathode potential. To explain this discrepancy, this study briefly examined the influence of electrode potential in two aspects: theoretical thermodynamics energy and the state of the hydrogen source near the electrode surface.

中文翻译：

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了解中性环境下析氢反应中电极电位对不同电荷氢源的影响


电化学水分解是降低制氢成本的一种有前景的策略。然而，传统的磷酸盐缓冲液 (PBS) 电解质在高过电势范围内会产生巨大的能量损失。本研究使用两种具有不同电荷特性的缓冲电解质研究析氢反应 (HER) 性能：H ₂ PO ₄ ^– /HPO ₄ （PBS pK _a = 6.90）和 IMZH ⁺ /IMZ（IMZS pK _a = 7.03）。在 Pt 微电极上，结果表明 PBS 的平台电流密度与电极电位密切相关，而 IMZS 未观察到这种趋势。此外，当使用负载在碳纸上的商业Pt/C纳米催化剂时，IMZS电解质中的平台电流密度现象消失，这归因于带正电的氢源的预富集效应。原位拉曼表征表明，随着电极电位逐渐变为负值，电化学界面上 H ₂ PO ₄ ^– 的构型发生变化。相比之下，IMZH ⁺ 的吸附构型在测试的电位范围内保持相当稳定。进一步采用隐式和显式溶剂化模型的大正则密度泛函理论方法研究了电极电位对不同电荷氢源解离的影响。结果表明，当电极电势逐渐变为负值时，H ₂ PO ₄ ^– 由于静电力而被电极表面排斥，从而增加了电极的吉布斯自由能。相应地解离。 这种现象导致了在 HER 的 PBS 电解质中观察到的不可避免的能量损失。相比之下，IMZH ⁺ 的吉布斯离解自由能随着负阴极电位的增加而单调降低。为了解释这种差异，本研究从理论热力学能量和电极表面附近氢源的状态两个方面简要考察了电极电势的影响。