A molecular design strategy to enhance hydrogen evolution on platinum electrocatalysts

Design of electrode–aqueous interfaces for hydrogen evolution reactions (HERs) is crucial to developing improved electrolysers. Modifications at the surface of electrodes have been employed to accelerate HER, but effective guiding principles are lacking. Here we establish a molecular design strategy to enhance HER activity in alkaline media by up to 50 times by introducing an organic overlayer on Pt electrodes. We find that enhancement of HER activity by organic adsorbates is correlated with their binding energies to Pt electrodes; binding energy could be tuned by changing the number of aromatic rings and hydrophilicity of the adsorbates. Density functional theory calculations suggest that the overlayer led to a decrease in the d-band centre, resulting in weakened H adsorption, which mitigated its overbinding on Pt. Importantly, we demonstrate the enhancing effect of the 2,2′-bipyrimidine overlayer on Pt/C in a water electrolyser with a membrane electrode assembly configuration, confirming its effectiveness on the device level.