Title: Elucidating contact electrification mechanism of water Show Chinese title

Title: 阐明水的接触起电机制

Abstract: The open water surface is known to be charged. Yet, the magnitude of the charge and the physical mechanism of the charging remain unclear, causing heated debates across the scientific community. Here we directly measure the charge Q of microdrops ejected from hydrophilic and hydrophobic capillaries and show that the water surface can take both positive or negative charge values depending on pH and the capillary type. Our experiments, theory, and simulations provide evidence that a junction of two aqueous interfaces with a different ion adsorption energy (e.g., liquid-solid and liquid-air interfaces) develops a pH-dependent contact potential difference {\Delta}{\phi} up to 52 mV. The longitudinal charge transfer between the interfaces stimulated by {\Delta}{\phi} determines the charge of the open water surface. The suggested static electrification mechanism provides far-reaching insights into the origin of electrical potentials in biological and electrochemical energy systems. Show Chinese abstract

Abstract: 已知开放的水表面带有电荷。然而，电荷的大小以及充电的物理机制仍然不清楚，这在科学界引发了激烈的争论。在这里，我们直接测量了从亲水性和疏水性毛细管中喷射出的微滴的电荷 Q，并表明水表面可以根据 pH 值和毛细管类型携带正或负电荷。我们的实验、理论和模拟提供了证据，表明两个具有不同离子吸附能的水界面（例如，液-固和液-空气界面）之间的结点会发展出依赖于 pH 的接触电势差{\Delta }{\phi } ，高达 52 mV。由{\Delta }{\phi } 激发的界面之间的纵向电荷转移决定了开放水表面的电荷。所提出的静态电离机制为生物和电化学能量系统中电势的起源提供了深远的见解。