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Formic acid (FA) as a safe and promising hydrogen carrier has attracted widespread attention. The use of solid catalysts in the controllable and efficient dehydrogenation of FA is still a challenge. Here, a series of Au nanoclusters supported on rare earth metal doped ZrO2 catalysts (Au/ReZrO2 (Re = Nd, Ce and Sm)) was prepared. Doping rare earth metals in zirconia stabilizes the mixed-phase zirconia into the tetragonal phase. Meanwhile, the rare earth metal dopants can promote the formation of oxygen vacancies in zirconia, which promotes charge transfer from the support to Au and enhances the metal–support interaction on all the three catalysts. As a result, Au/ReZrO2 (Re = Nd3+, Ce3+ and Sm3+) catalysts exhibited better catalytic performance in the liberation of CO-free H2 from FA, outperforming Au supported on primary ZrO2. Structural and electronic characterization by XPS and H2-TPR further confirmed the contribution of doping rare earth metal cations in Au/ReZrO2, which can enhance the metal–support interaction and accelerate the decomposition of HCOOH into H2, thus resulting in the improvement in catalytic activity for hydrogen production from FA. [ABSTRACT FROM AUTHOR]

A nano-confined pyrolysis approach was developed for constructing highly nitrogen-doped hierarchically porous metal/N/C nanospheres (typically Fe/N/C-HP). Hierarchically porous silica nanospheres (NKM-5) were used as a hard template, and an amorphous Fe/Zn-(MeIm)2 complex was employed as a carbon and nitrogen source. During the pyrolysis process, first, the molten Fe/Zn-(MeIm)2 complex diffused into hierarchically porous tunnels of NKM-5. Secondly, the interface confinement effect of nanopores in NKM-5 could effectively immobilize nitrogen to coordinate with iron atom, prevent the aggregation of Fe-based species and form single-atom Fe sites. After the silica template was removed, the catalyst exhibited a hierarchically porous structure and uniform spherical morphology. This hierarchically porous structure of Fe/N/C-HP can enhance mass transport/electron transfer and greatly improve the accessibility of Fe/N/C sites. As a result, the Fe/N/C-HP catalyst exhibits excellent oxygen reduction performance with a half-wave potential (E1/2) of 0.90 V in alkaline media and 0.78 V in acidic media. A primary Zn–air battery with Fe/N/C-HP as the cathode catalyst exhibits a large peak power density of 181 mW cm−2 and discharge stability. This nano-confined pyrolysis of amorphous M/Zn-(MeIm)2 complex is a general method to construct a hierarchically porous M/N/C (M = Fe, Co, Cu, Mn and Ni) electrocatalyst with well-defined morphology. [ABSTRACT FROM AUTHOR]

Ultrafine and highly dispersed PdAu nanoparticles were immobilized on amine functionalized carbon black (VXC-72-NH 2 ) for dehydrogenation of formic acid (FA). The introduction of amines is of vital importance for the formation of ultrafine PdAu nanoparticles (∼1.5 nm). Moreover, the presence of the amino groups also increased the electron density of PdAu nanoparticles, and this effect facilitated the formation of metal-formate, which further enhanced the rate of the catalytic dehydrogenation of FA. The as-prepared Pd 0.6 Au 0.4 /VXC-72-NH 2 exhibited high catalytic activity and 100% H 2 selectivity for dehydrogenation of formic acid without any additive, with turnover frequency (TOF) values of 7385 h -1 at 298 K and 17 724 h -1 at 333 K, which are the highest TOF values ever reported among heterogeneous catalysts for FA dehydrogenation., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)