Discrimination And Regulation Of Active Sites Over Carbon-Supported Pt-Based Catalyzed Hydrogen Evolution

Hydrogen evolution reaction(HER)plays a significant role in obtaining high-purity hydrogen and achieving sustainable distributed storage of hydrogen energy.Although commercial Pt/C catalysts show state-of-the-art HER activity,their large-scale commercialization is limited by its high expense,low Pt atom utilization and poor long-term stability.To this end,from the viewpoint of catalyst active sites,model calculations are first employed to discriminate the main active sites of Pt/C catalyst.Then,the microstructures and properties of the catalyst active sites are correlated with the HER activity,kinetics behavior and stability,aiming to reveal the underlying nature of the catalyst structure-performance relations.Finally,the well-fabircated Pt/C catalysts with simultaneously high atom-utilization efficiency and stability are developed.The main findings are shown below:(1)Based on the model calculations,by plotting the catalyst activity(TOF)of each type Pt sites with the Pt particle size of the metal particles can discriminate the Pt(100)surface as the dominant active sites of HER.The underlying nature of the Pt particle size effects is revealed.When the Pt particle size is≥ 2.1 nm,the difference in the HER activity is mainly due to the changed number of Pt active sites with the Pt particle size.In addition,when the Pt particle size is<2.1 nm,there are significant electronic effects,in which the electron-deficient Pt particles show higher HER activity.(2)Changing the types of Pt precursors as well as the reduction method and atmosphere is employed to tune the number of active sites,local environments and electronic properties of Pt-based catalysts.It is found that the resultant Pt/C catalysts by using H2PtCl6·6H2O precursor and hydrogen plasma reduction method show uniform,highly dispersed and Pt-Cl bond-free Pt nanoparticles with high Pt electron binding energy,which give rise to a significantly improved HER activity.Compared with the commercial Pt/C at a current density of 10 mA cm-2,the HER activity of the Pt/C catalyst is increased by 35%.Moreover,the Tafel kinetics analysis indicates the change in the dominant HER mechanism from Volmer-Heyrovsky to Volmer-Tafel mechanism as Pt electron binding energy increases,greatly increasing the HER activity.(3)A new method of using hydrothermal oxidation modified carbon black as a support and using atomic layer deposition technology to fabricate a Pt/C catalyst with high atomic utilization and stability is developed.The carboxyl functional groups on the surfaces of the carbon support is found to not only effectively anchor the highly dispersed Pt nanoparticles,but also significantly regulate the Pt electronic structure.The as-obtained Pt/C catalyst has an overpotential of 23 mV under a current density of 10 mA cm-2,while the overpotential is only 19 mV after 3000 cycles of CV scans.Furthermore,compared with the commercial Pt/C catalysts,the HER activity is increased by 25%with the 26 times stability increasing.