Elucidating the Action Mechanism of the Carbon Substrate in Pt/C-Catalyzed Alkaline Hydrogen Evolution Reaction

In the alkaline hydrogen evolution reaction (HER), loading Pt on a carbon substrate can markedly enhance its activity. Electrochemical tests show that the Tafel slopes of Pt/C and Pt mesh are 73 and 171 mV dec–1, respectively, which indicate the HER mechanisms on Pt/C and Pt are different. In alkaline media, the HER on Pt is limited by H2O dissociation. Therefore, in this paper, the effect of the carbon substrate on the H2O dissociation process on a Pt cluster was systematically studied by density functional theory (DFT) calculations. The results indicate that the electron redistribution of the Pt cluster caused by the carbon substrate can enhance the Lewis acidity of the active site, thereby accelerating H2O dissociation step on the Pt cluster. Therefore, promoting the H2O dissociation step on Pt by the carbon substrate is one of the prime reasons for the eminent activity of Pt/C in the alkaline HER.