Boosting Hydrogen Evolution Activities by Strong Interfacial Electronic Interaction in ZnO@Bi(NO3)3 Core-Shell Structures

Base-free hydrogen evolution from formaldehyde solution represents one of the most important reactions in the fuel cell based hydrogen economy. However, limited progresses have been made in the rational design of cheap and efficient heterogeneous catalysts for this reaction. Here, we for the first time propose a Lewis acid-base combination strategy to design efficient heterogeneous catalysts for HER from HCHO/H2O. By utilizing the Lewis acid/base properties of Bi(NO3)(3)center dot 5H(2)O/ZnO, we successfully fabricated core-shell structured ZnO@Bi(NO3)(3) composites. A strong interfacial electronic interaction between ZnO and Bi(NO3)(3)center dot 5H(2)O is evidenced by the unprecedented 3.3 eV upshift of Zn 2p and 0.5 eV downshift of Bi 4f, which boosts the HER activities of inert ZnO and Bi(NO3)(3)center dot 5H(2)O. Destroying the interfacial electronic interaction leads to a fast deactivation while increasing interfacial sites proportionally enhances the activity, indicating that interfacial sites are real active sites. DFT calculations confirm that ZnO@Bi(NO3)(3) composites greatly lower the activation barrier of H-2 formation from two adsorbed H atoms and thus promote the H-2 production. The Lewis acid-base combination strategy also applies to the TiO2@Bi(NO3)(3) system, further highlighting the importance of salt-metal oxide interface in heterogeneous catalysis.