PT  - JOURNAL ARTICLE
AU  - Le, Jia-Bo
AU  - Fan, Qi-Yuan
AU  - Li, Jie-Qiong
AU  - Cheng, Jun
TI  - Molecular origin of negative component of Helmholtz capacitance at electrified Pt(111)/water interface
AID  - 10.1126/sciadv.abb1219
DP  - 2020 Oct 01
TA  - Science Advances
PG  - eabb1219
VI  - 6
IP  - 41
4099  - http://advances.sciencemag.org/content/6/41/eabb1219.short
4100  - http://advances.sciencemag.org/content/6/41/eabb1219.full
SO  - Sci Adv2020 Oct 01; 6
AB  - Electrified solid/liquid interfaces are the key to many physicochemical processes in a myriad of areas including electrochemistry and colloid science. With tremendous efforts devoted to this topic, it is unexpected that molecular-level understanding of electric double layers is still lacking. Particularly, it is perplexing why compact Helmholtz layers often show bell-shaped differential capacitances on metal electrodes, as this would suggest a negative capacitance in some layer of interface water. Here, we report state-of-the-art ab initio molecular dynamics simulations of electrified Pt(111)/water interfaces, aiming at unraveling the structure and capacitive behavior of interface water. Our calculation reproduces the bell-shaped differential Helmholtz capacitance and shows that the interface water follows the Frumkin adsorption isotherm when varying the electrode potential, leading to a peculiar negative capacitive response. Our work provides valuable insight into the structure and capacitance of interface water, which can help understand important processes in electrocatalysis and energy storage in supercapacitors.