Disruption of hydrogen bond structure of water near charged electrode surfaces

The understanding of the hydrogen (H) bonded structure of water near charged surfaces is highly relevant in the context of several important areas of research, including electrochemistry, biochemistry, and geology. Past simulation studies have not yielded conclusive answers; while some suggest breakage of H bonds near a charged surface, others argue that H-bonding interactions can stabilize the structure of surface water even in the presence of high electric (E) fields. Recent experiments, on the other hand, suggest a partial breakdown of H-bond structure near a charged electrode. In all these studies, however, the conclusions regarding H bonding were drawn based on the density profile of hydrogen/oxygen atoms near the interface. In the present paper, we investigate this problem using a new theory that explicitly accounts for the influence of E field on the H-bond network of water near the solid-liquid interface. We find that the average number of H bonds per molecule in bulk increases from approximately 3.8 at E<10(5) V/m to approximately 3.95 at E=2x10(9) V/m (suggesting enhancement in H-bond network), while that near the electrode surface decreases from approximately 2.8 to a saturation value of approximately 2.0 (suggesting weakening of H-bond network).