Abstract
Identification of the active site is important in developing rational design strategies for solid catalysts but is seriously blocked by their structural complexity. Here, we use uniform Cu nanocrystals synthesized by a morphology-preserved reduction of corresponding uniform Cu2O nanocrystals in order to identify the most active Cu facet for low-temperature water gas shift (WGS) reaction. Cu cubes enclosed with {100} facets are very active in catalyzing the WGS reaction up to 548 K while Cu octahedra enclosed with {111} facets are inactive. The Cu–Cu suboxide (CuxO, x ≥ 10) interface of Cu(100) surface is the active site on which all elementary surface reactions within the catalytic cycle proceed smoothly. However, the formate intermediate was found stable at the Cu–CuxO interface of Cu(111) surface with consequent accumulation and poisoning of the surface at low temperatures. Thereafter, Cu cubes-supported ZnO catalysts are successfully developed with extremely high activity in low-temperature WGS reaction.
Highlights
Identification of the active site is important in developing rational design strategies for solid catalysts but is seriously blocked by their structural complexity
We report the identification of the most active Cu facet for low-temperature water gas shift (WGS) reaction up to 548 K employing uniform capping ligands-free Cu NCs synthesized by a morphology-preserved reduction of corresponding uniform Cu2O NCs
The Cu–Cu suboxide (CuxO, x ≥ 10) interface of Cu (100) surface is the active site on which all elementary surface reactions within the catalytic cycle proceed smoothly, but the Cu–CuxO interface of Cu(111) surface is poisoned by an accumulation of formate intermediate stable at low reaction temperatures
Summary
Identification of the active site is important in developing rational design strategies for solid catalysts but is seriously blocked by their structural complexity. The above comprehensive characterization results demonstrate a successful synthesis of uniform c-Cu, o-Cu, and d-Cu NCs respectively with well-defined {100}, {111}, and {110} surfaces via a morphology-preserved reduction of corresponding c-Cu2O, o-Cu2O, and d-Cu2O NCs. Effect of Cu facet on activity.
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