Ultrathin PtPd‐Based Nanorings with Abundant Step Atoms Enhance Oxygen Catalysis

Abstract

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 and 4.90 mA cm 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 ) 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.

Low‐Coordinate Step Atoms via Plasma‐Assisted Calcinations to Enhance Electrochemical Reduction of Nitrogen to Ammonia

“…By combining the theory of crystal structure analysis and simulation of the HAADF‐STEM image (see detail in Figure S3 in the Supporting Information), it can be accurately deduced that a large density of high‐index facets, such as {202}, {212}, and {313}, frequently emerge around the irregular surfaces of IrP 2 nanocrystals, strongly verifying the existence of low‐coordinate atomic steps. [ 16,20,30 ] To corroborate the distributions of the Ir, P, C, and N elements in IrP 2 @PNPC‐NF, mapping analysis and line scans were performed in scanning transmission electron microscopy energy‐dispersive X‐ray spectroscopy (STEM‐EDX) (Figure 1e). As shown in Figure 1f–j, it is clear that the C and N elements are homogeneously distributed over the whole selected area, while Ir and P are mainly concentrated in the bright portion shown in Figure 1e, thus further implying the formation of IrP 2 nanocrystals.…”

“…To address this critical but thorny problem, stepped facets and doping modification may be the two effective ways to intrinsically enhance their catalytic activity. [ 16–21 ] On the one hand, stepped facets usually have low coordination number (CN) of surface atoms, where these unsaturated sites can more favorably adsorb and activate N 2 molecule compared with the flat facets. [ 22 ] For example, Zhang's group reported tetrahexahedral gold nanorods enclosed by stepped {730} facets that exhibit unexpectedly electrocatalytic NRR performance, indicating low‐coordinate step atoms are the favorable active sites in optimizing the activity of the metal‐based catalysts.…”

Rh-doped PdAg nanoparticles as efficient methanol tolerance electrocatalytic materials for oxygen reduction

“…The peaks of Rh 4 Pd 40 Ag 56 NPs are those between fcc Pd (JCPDS No. 46-1043) [50] and fcc Ag (JCPDS No. 04-0783) [51] (Fig.…”

Ultrathin‐Polyaniline‐Coated Pt–Ni Alloy Nanooctahedra for the Electrochemical Methanol Oxidation Reaction

“…Platinum nanomaterials have been considered to be highly efficient electrocatalysts of academic and industrial importance in polymer electrolyte membrane fuel cells (PEMFCs) for decades. [1][2][3][4] However,P tc atalysts are severely restricted by high cost and limited Pt reserves. [5,6] Furthermore, inadequate activity and durability,w hich have been attributed to shape deformation and surface poisoning of Pt catalysts by strong adsorption of intermediate speciesd uring electrocatalytic reactions, are other significant issues that remaint ob eo vercome in terms of their application in PEMFCs.…”