There are numerous examples of catalysts used to speed up the production of H2 in hydrogen evolution reactions (HERs) under either acidic or basic conditions. At neutral pH, however, the kinetics become sluggish, but could be improved with catalyst interfaces designed to better facilitate mass transport, thus expanding the scope of future applications such as fuel cell designs for seawater-based electrocatalytic water splitting.

The hydrogen bonded network of water at a heterogeneous interface greatly impacts HER kinetics. Only a small subset of the bulk water electrolyte will interface with the electrode surface. The growth of rigid interfacial water networks participating in hydrogen bonding with an electrode surface creates ‘ice-like’ and ‘liquid-like’ water, that slows H2O dissociation and impedes the transport of ions to the catalyst surface. Interestingly, free water interfaces have been shown to promote HER activity (see figure).