Electrochemical Deposition of Pt Nanoclusters on WC for Hydrogen Evolution Reaction in Acid
Fig. 1 shows Pt deposition as a function of applied potential from a NaCl-supporting electrolyte. An interesting finding is that the deposition of Pt is prevented at potentials below -0.5 V, in spite of high driving forces for Pt clusters to form and grow. This talk will present ways in which this anomalous deposition behavior can be exploited for preparing novel Pt catalysts. A brief summary will be given for Pt deposition on Au [] and Ni [] electrodes where a monolayer-thick Pt film is deposited at -0.8 V but additional growth is quenched. For WC substrates, we will discuss challenges associated with the lack of Pt depositing at -0.80 V, before introducing to a new approach that is developed to facilitate the formation of Pt nuclei.
The proposed method involves cycling the potential between -0.8 V and -0.45 V at a fast rate of 50 mV/s. As shown in Fig. 2, Pt nanoclusters with high particle density could be grown on WC, and their average size is about 5 nm. To gain mechanistic insights on Pt nanostructure nucleation and growth, the deposits were analyzed using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and underpotentially deposited (UPD) hydrogen and copper. Correlations between deposition potential cycle and particle growth and particle density will be discussed.
Finally, Pt deposits were examined as catalysts for HER in 0.5 M sulfuric acid. The dependence of HER activity on the number of deposition cycles is shown in Fig. 3 where the HER activity approaches that of bulk platinum as the deposition cycles increase even though the expected total amount of platinum is far less than a complete coverage. This work illustrates that electrodeposition provides a simple and scalable way for preparing Pt nanocluster/WC catalysts, which exhibit high activity and durability toward HER in acid media.