Professor Xiaolin Zheng, Mechanical Engineering, Energy Science & Engineering, Stanford University

Beyond Photoelectrochemical Water Splitting: from Hydrogen Production to Water Disinfection

ABSTRACT Photoelectrochemical (PEC) water splitting area has been investigated for decades as a means to convert sunlight to fuels. To date, PEC still faces many challenges, ranging from low efficiency, poor stability, and non-competitive cost. I will present two examples of our recent efforts in overcoming some of the challenges facing PEC. The first example is related to the well-known hydrogen evolution reaction (HER) catalyst, MoS2. For MoS2, the perfect basal plane is long regarded as inert, but it can be activated for HER by creating S-vacancies. The activity of the S-vacancy can also be further improved by either strain or transition metal doping. The second example is switched to the water oxidation side of water splitting. So far, most research on water oxidation has been focusing on producing O2. Here, I will discuss the potential of using the competing two-electron water oxidation pathway to produce a valuable chemical, i.e., H2O2. Importantly, such a reaction can be coupled with oxygen reduction to H2O2 reaction to construct an unassisted PEC system, which uses light, water, and oxygen to simultaneously produce electricity and H2O2: Light + 2H2O + O2 = Electricity + 2H2O2. This new unassisted PEC system demonstrates an alternative solar-chemical pathway by using sunlight and water.

BIOGRAPHY Xiaolin Zheng is a Professor of Mechanical Engineering and Energy Science & Engineering at Stanford University. She received her B.S. in Thermal Engineering from Tsinghua University (2000), her Ph.D. in Mechanical & Aerospace Engineering from Princeton University (2006), and her postdoctoral training in the Department of Chemistry and Chemical Biology at Harvard University.

Her research group focuses on the development and testing of novel materials for energy and propulsion applications, ranging from combustion synthesis of novel nanomaterials, designing electrocatalysts and devices to convert water into hydrogen, oxygen, and hydrogen peroxides, to developing new metal/polymer composites as high energy density fuels for propulsion applications.

She is a senior fellow of Stanford Precourt Institute of Energy, and a faculty co-director of Stanford Hydrogen Initiative. Her selected awards include the Resonate Award from Resnick Institute at Caltech (2016), Nano Letters Young Investigator Lectureship (2015), MIT Technology Review (2013), one of the 100 Leading Global Thinkers by the Foreign Policy Magazine (2013), Presidential Early Career Award for Scientists and Engineers (PECASE) from the White House (2009).