A pinboard by
Siwen Wang

PhD candidate, Virginia Polytechnic Institute and State University


This research is about computational catalysis and surface science, energy capture and storage

My research focuses on modeling structure-function relationships of nanoscale assemblies for energy and electronics applications. Ongoing research includes design of hybrid materials for catalysis, solar energy capture and storage, charge transport, etc. This research will be supported by a collaborative effort in assembling diverse classes of functional materials on the nanoscale. To guide materials design, special attention has been given to the development of a multiscale modeling framework that integrates our expertise in ab-initio calculations, kinetic simulations, and statistical learning. Motivated by recent advances in ultrafast science, we specifically tackle challenging problems in energy and electronics that require fundamental understanding of atomistic and charge dynamics at interfaces.


Ag-Sn Bimetallic Catalyst with a Core-Shell Structure for CO2 Reduction.

Abstract: Converting greenhouse gas carbon dioxide (CO2) to value-added chemicals is an appealing approach to tackle CO2 emission challenges. The chemical transformation of CO2 requires suitable catalysts that can lower the activation energy barrier, thus minimizing the energy penalty associated with the CO2 reduction reaction. First-row transition metals are potential candidates as catalysts for electrochemical CO2 reduction; however, their high oxygen affinity makes them easy to be oxidized, which could, in turn, strongly affect the catalytic properties of metal-based catalysts. In this work, we propose a strategy to synthesize Ag-Sn electrocatalysts with a core-shell nanostructure that contains a bimetallic core responsible for high electronic conductivity and an ultra-thin partially oxidized shell for catalytic CO2 conversion. This concept was demonstrated by a series of Ag-Sn bimetallic electrocatalysts. At an optimal SnOx shell thickness of ~1.7 nm, the catalyst exhibited a high formate Faradaic efficiency of ~80% and a formate partial current density of ~16 mA cm(-2) at -0.8 V vs. RHE, a remarkable performance in comparison to state-of-the-art formate-selective CO2 reduction catalysts. Density-functional theory calculations showed that oxygen vacancies on the SnO (101) surface are stable at highly negative potentials and crucial for CO2 activation. In addition, the adsorption energy of CO2- at these oxygen-vacant sites can be used as the descriptor for catalytic performance because of its linear correlation to OCHO* and COOH*, two critical intermediates for the HCOOH and CO formation pathways, respectively. The volcano-like relationship between catalytic activity towards formate as a function of the bulk Sn concentration arises from the competing effects of favorable stabilization of OCHO* by lattice expansion and the electron conductivity loss due to the increased thickness of the SnOx layer.

Pub.: 18 Jan '17, Pinned: 04 Jul '17