RESUMEN
Direct methanol fuel cells (DMFCs) have received extensive attention on their high efficiency, high reliability, and no carbon emission. Unfortunately, the poor methanol tolerance and sluggish oxygen reduction reaction (ORR) at cathode have seriously hindered their further development. Herein we report the synthesis of a new class of Rh-doped PdAg alloy nanoparticles (NPs) for boosting ORR activity with high methanol tolerance capacity concurrently. The ORR mass activity of typical Rh4Pd40Ag56 NPs is 4.2 times higher than that of commercial Pt catalyst. Moreover, it shows a great methanol tolerance capability by maintaining 92.4% in ORR mass activity in alkaline solution with 0.1â¯molâ¯L-1 methanol, against a big decrease of almost 100% for commercial Pt. Even after 30,000 potential cycles with 1.0â¯molâ¯L-1 methanol, Rh4Pd40Ag56 NPs still retain ORR mass activity of up to 68.3%. DFT calculations reveal that excellent ORR performance with excellent methanol tolerance originates the active d-band-pinning engineering for an efficient site-independent electron-transfer. A generalized d-band mediated fine electron-transfer tuning path has blueprinted for effectively minimizing intrinsic ORR barriers with high current density. The present work highlights the key role of Rh doping in enhancing the ORR activity and methanol tolerance ability of PdAg NPs for future high-performance DMFCs.
RESUMEN
The lack of highly active and stable catalysts with low Pt usage for the oxygen reduction reaction (ORR) is a major barrier in realizing fuel cell-driven transportation applications. A general colloidal chemistry method is demonstrated for making a series of ultrathin PtPdM (M = Co, Ni, Fe) nanorings (NRs) for greatly boosting ORR catalysis. Different from the traditional ultrathin nanosheets, the ultrathin PtPdM NRs herein have a high portion of step atoms on the edge, high Pt utilization efficiency, and strong ligand effect from M to Pt and fast mass transport of reactants to the NRs. These key features make them exhibit greatly enhanced electrocatalytic activity for the ORR and the oxygen evolution reaction (OER). Among all the PtPdM NRs, the PtPdCo shows the highest ORR mass and specific activities of 3.58 A mg-1 and 4.90 mA cm-2 at 0.9 V versus reversible hydrogen electrode (RHE), 23.9 and 24.5-fold larger than those of commercial Pt/C in alkaline electrolyte, respectively. The theoretical calculations reveal that the oxygen adsorption energy (E O ) can be optimized under the presence of step atoms exposed on the edge and ligand effect induced by Co. They are stable under ORR conditions with negligible changes after 30 000 cycles.
RESUMEN
H2O2 sensors with high sensitivity and selectivity are essential for monitoring the normal activities of cells. Inorganic catalytic nanomaterials show the obvious advantage in boosting the sensitivity of H2O2 sensors; however, the H2O2 detection limit of reported inorganic catalysts is still limited, which is not suitable for high-sensitivity detection of H2O2 in real cells. Herein, novel atomic-thick PtNi nanowires (NWs) were synthesized and assembled on reduced graphene oxide (rGO) via an ultrasonic self-assembly method to attain PtNi NWs/rGO composite for boosting the electroanalysis of H2O2. In 0.05 M phosphate-buffered saline (pH 7.4) solution, the as-prepared PtNi NWs/rGO shows an extraordinary performance in quantifying H2O2 in a wide range of concentrations from 1 nM to 5.3 mM. Significantly, the detection limit of PtNi NWs/rGO reaches unprecedented 0.3 nM at an applied potential of -0.6 V (vs Ag/AgCl), which enables the detection of traced amounts of H2O2 released from Raw 264.7 cells. The excellent performance of H2O2 detection on PtNi NWs/rGO is ascribed to the high-density active sites of atomic-thick PtNi NWs.