Building Fe atom–cluster composite sites using a site occupation strategy to boost electrochemical oxygen reduction

The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic clusters to nanoparticles.Therefore,understanding the interactions among these components,especially the synergistic effects between single atomic sites and cluster sites,is crucial for improving the oxygen reduction reaction(ORR)activity of M–N–C catalysts.Accordingly,herein,we constructed a model catalyst composed of both atomically dispersed FeN4 SA sites and adjacent Fe clusters through a site occupation strategy.We found that the Fe clusters can optimize the adsorption strength of oxygen reduction intermediates on FeN4 SA sites by introducing electron-withdrawing–OH ligands and decreasing the d-band center of the Fe center.The as-developed catalyst exhibits encouraging ORR activity with halfwave potentials(E1/2)of 0.831 and 0.905 V in acidic and alkaline media,respectively.Moreover,the catalyst also represents excellent durability exceeding that of Fe–N–C SA catalyst.The practical application of Fe(Cd)–CNx catalyst is further validated by its superior activity and stability in a metalair battery device.Our work exhibits the great potential of synergistic effects between multiphase metal species for improvements of singleatom site catalysts.

Engineering the HER catalytic behavior of heteroatom-doped molybdenum disulfide via versatile partial cation exchange

Water electrolysis is regarded as an environmental friendly and effective technique for large-scale hydrogen(H2)production[1,2].To date,Pt-based electrocatalysts are still the most efficient HER catalysts[3].However,the prohibitive cost and scarcity of precious metal catalysts have restricted its large-scale applications.Thus,finding an earth-abundant and effective alternative electrocatalysts is crucial to the development of‘hydrogen economy'.

Carbon monoxide powered fuel cell towards H_(2)-onboard purification

Proton exchange membrane fuel cells(PEMFCs)suffer extreme CO poisoning even at PPM level(<10 ppm),owning to the preferential CO adsorption and the consequential blockage of the catalyst surface.Herein,however,we report that CO itself can become an easily convertible fuel in PEMFC using atomically dispersed Rh catalysts(Rh-N-C).With CO to CO_(2) conversion initiates at 0 V,pure CO powered fuel cell attains unprecedented power density at 236 mW cm^(-2),with maximum CO turnover frequency(64.65 s^(-1),363 K)far exceeding any chemical or electrochemical catalysts reported.Moreover,this feature enables efficient CO selective removal from H_(2) gas stream through the PEMFC technique,with CO concentration reduced by one order of magnitude through running only one single cell,while simultaneously harvesting electricity.We attribute such catalytic behavior to the weak CO adsorption and the co-activation of H_(2)O due to the interplay between two adjacent Rh sites.