Ligand Charge Donation-Acquisition Balance: A Unique Strategy to Boost Single Pt Atom Catalyst Mass Activity toward the Hydrogen Evolution Reaction

Developing oxide supports for stabilizing single-atom catalysts enables more flexibility for tuning the electronic metal-support interactions (EMSIs) toward better catalytic activities. However, due to the electronegativity of oxygen anions, single-metal atoms often remain positively charged in these oxide supports and are poor at binding hydrogen species for the hydrogen evolution reaction (HER). Here, we report a ligand charge donation-acquisition balance strategy via an amorphous TiBxOy, support to tune the EMSIs, which lead to the boosted HER mass activity of a single Pt atom catalyst. Based on spectroscopic characterizations, we found that Pt single atoms preferentially bonded with nearly neutral B atoms originating from TiB2-like species in the Ti-B-O framework rather than O anions. Density functional theory calculations reveal that due to the charge-transfer balance between B-O and B-Pt, the nucleophilicity of Pt was tuned to an optimum state, with an ideal hydrogen binding energy that benefits the HER. As a result, this Pt/TiBxOy catalyst achieves a high HER mass activity (37.8 A mg(-1) Pt) and a turnover frequency (33.2 H-2 s(-1) Pt site(-1)) at an overpotential of 50 mV in an acid medium, outperforming commercial Pt/C by a factor of 34 and 33, respectively.