(678f) First-Principles Study of Hydrogen Production on ZnO Supported Single-Atom Catalysts

Single-atom catalysts have attracted considerable interests in heterogeneous catalysis recently. These single atoms generally stabilized by lattice oxygen of oxide supports or alkali metals with the benefits of highest atomic efficiency and structural simplicity. Moreover, their promising catalytic activity has been reported for CO oxidation and water gas shift reaction (WGSR). However, it is still an open question that how to rational design single-atom catalyst for a certain catalytic reaction. Here we report that design of ZnO supported single atoms for hydrogen production from methanol steam reforming (MSR) and WGSR via density functional theory (DFT) calculations combined with experimental study. We found that the single Pt₁ and Au₁ atoms stabilized by lattice oxygen of ZnO surface have significantly higher activity for MSR. It is revealed that the catalysis of these single precious metal atoms together with coordinated lattice oxygen stems from its stronger binding towards the intermediates, lower reaction barriers, changing on the reaction pathway. The measured turn-over-frequency of single Pt₁ sites was more than 1000 times higher than the pristine ZnO. For WGSR on ZnO supported single transition metal atoms, we found that the activity of WGSR via favorable associative mechanism can be tuned by changing single atom. Based on microkinetic modeling analysis, a volcano-like relationship between calculated rates and binding energies of COOH intermediate was found. Among single transition metal atoms considered here, Ni₁/ZnO has the highest activity of WGSR. These results provide valuable insights into the catalysis of the atomically dispersed metals on oxide supports.

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