Structural Engineering of Functional Nanomaterials for Electrochemical Energy Conversions

Shaowei Chen 

University of California

Abstract: Development of effective technologies for clean and sustainable hydrogen energy has been attracting great attention. Toward this end, a promising approach is based on the electrolysis of water for hydrogen production. To date, the most effective electrocatalysts towards hydrogen evolution reaction (HER) are based on Pt-group metals. However, the high costs and natural scarcity have severely limited their broad utilization. Transition-metal compounds have been prepared as effective, alternative HER catalysts in a series of recent studies. However, thus far, it has remained a great challenge to develop highly active HER catalysts with a low overpotential based on earth-abundant and cost-effective materials. Recently, carbon-based electrocatalysts have attracted a great deal of interest because of their low overpotentials toward HER. Notably, the active sites of carbon for HER can be modulated by the incorporation of transition metal nanoparticles and (non)metal doping. In this presentation, we will summarize recent progress in the development of carbon-based electrocatalysts toward HER. In particular, we will report recent development in the design and engineering of single-atom catalysts for HER, which is exemplified with graphitic carbon nitride (C3N4) nanosheets embedded with ruthenium ions. This takes advantage of the strong affinity of ruthenium ions to pyridinic nitrogen of the tri-s-triazine units of C3N4. Significantly, the hybrid materials exhibit apparent electrocatalytic activity towards HER in acid and the activity increases with the loading of ruthenium metal centers in the C3N4 matrix. Control experiments show only markedly reduced activity with other transition metal ions such as Fe3+, Ni3+, Co3+ and Cu2+, and minimal contributions from the C3N4 nanosheets to the HER activity. The activity is most likely due to the formation of Ru-N moieties where the synergistic interactions between the carbon nitride and ruthenium metal centers facilitate the adsorption of hydrogen due to charge redistribution. This is strongly supported by results from density functional theory calculations.

Biography:Shaowei Chen finished his undergraduate studies in China in 1991 with a BS degree in Chemistry from the University of Science and Technology of China, and then went to Cornell University receiving his MS and PhD degrees in 1993 and 1996 respectively. Following a postdoctoral appointment in the University of North Carolina at Chapel Hill, he started his independent career in Southern Illinois University in 1998. In summer 2004, he moved to the University of California at Santa Cruz (UCSC). He is currently a Professor of Chemistry and the Faculty Director of the UCSC COSMOS program. He has also been an adjunct professor in South China University of Technology since 2012.