Research conducted at the Tufts Nano-CEL aims at applying principles of
heterogeneous catalysis to the solution of problems in the production of
hydrogen and green chemicals.
A major research effort is in the area of catalytic hydrogen production
reactions; e.g. fuel conversion to synthesis gas; steam reforming of hydrocarbons
and alcohols; and the water-gas shift reaction. Effective catalysts for these
reactions are highly dispersed metals (Au, Pt, Pd, Cu) on certain oxide supports.
We investigate the catalyst structure-activity relationships in these systems
by following specific metal structures (atoms, clusters, particles) and their
activity and stability on selected oxides; and by evaluating the potential shape
and crystal plane effect of oxides through careful preparation of the latter at
the nanoscale according to novel synthesis techniques.
An important reaction in all fuel conversions is the water-gas shift reaction
used to upgrade hydrogen gas streams. We have recently demonstrated that the active
sites for this reaction are single-atoms bound to various supports through -O, and
this holds true for [Au-Ox-], [Pt-Ox-}, [Cu-Ox-], etc.. The supports serve as dispersants
of the active sites, but do not participate in the reaction pathway, other than to supply ľOH,
which is regenerated by facile H2O dissociation. The oxide structure and its defects
control the dispersion of atom sites, and hence the overall catalytic activity.
Similar findings were reported for alcohol dehydrogenation and steam reforming reactions.
To study these atomic-scale interactions, controlled synthesis techniques are used,
as well as advanced characterization techniques to follow the structural evolution of
the catalyst in situ as a function of the reaction conditions.
Another area of research is that of selective hydrogenation and dehydrogenation
reactions using single atom alloys. These are alloys of a selective but low-activity
metal like Cu with small amounts of an active but non selective metal like Pd or Pt,
the latter present as atoms embedded in the surface of Cu. The new catalysts are
bifunctional, H2 dissociation taking place on the Pd or Pt, spillover to Cu, where
the reaction takes place. This was demonstrated for the selective hydrogenation of
alkynes and alkadienes both SAAs of Pt or Pd/Cu(111) and on Cu nanoparticle supported
on silica or alumina.
Work at the NanoCEL also supports research underway at the IMASC
(Integrated Mesoscale Architectures for Sustainable Catalysis), a DOE Energy Frontier
Research Center (EFRC) directed by Prof. Cynthia Friend, Harvard University.
Information about the IMASC center's activities >