Development of efficient and robust electrocatalysts is critical for practical fuel cells. We report one-dimensional bunched platinum-nickel (Pt-Ni) alloy nanocages with a Pt-skin structure for the oxygen reduction reaction that display high mass activity (3.52 amperes per milligram platinum) and specific activity (5.16 milliamperes per square centimeter platinum), or nearly 17 and 14 times higher as compared with a commercial platinum on carbon (Pt/C) catalyst. The catalyst exhibits high stability with negligible activity decay after 50,000 cycles. Both the experimental results and theoretical calculations reveal the existence of fewer strongly bonded platinum-oxygen (Pt-O) sites induced by the strain and ligand effects. Moreover, the fuel cell assembled by this catalyst delivers a current density of 1.5 amperes per square centimeter at 0.6 volts and can operate steadily for at least 180 hours.
Ac ompetitive complexation strategy has been developed to construct an ovel electrocatalyst with Zn-Co atomic pairs coordinated on Nd oped carbon support (Zn/ CoN-C). Sucha rchitecture offers enhanced binding ability of O 2 ,s ignificantly elongates the O À Ol ength (from 1.23 to 1.42 ), and thus facilitates the cleavage of O À Ob ond, showing at heoretical overpotential of 0.335 Vd uring ORR process.A saresult, the Zn/CoN-C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions with ah alf-wave potential of 0.861 and 0.796 Vr espectively. The in situ XANES analysis suggests Co as the active center during the ORR. The assembled zinc-air battery with Zn/CoN-Ca sc athode catalyst presents am aximum power density of 230 mW cm À2 along with excellent operation durability.T he excellent catalytic activity in acid is also verified by H 2 /O 2 fuel cell tests (peak power density of 705 mW cm À2 ).
A competitive complexation strategy has been developed to construct a novel electrocatalyst with Zn‐Co atomic pairs coordinated on N doped carbon support (Zn/CoN‐C). Such architecture offers enhanced binding ability of O2, significantly elongates the O−O length (from 1.23 Å to 1.42 Å), and thus facilitates the cleavage of O−O bond, showing a theoretical overpotential of 0.335 V during ORR process. As a result, the Zn/CoN‐C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions with a half‐wave potential of 0.861 and 0.796 V respectively. The in situ XANES analysis suggests Co as the active center during the ORR. The assembled zinc–air battery with Zn/CoN‐C as cathode catalyst presents a maximum power density of 230 mW cm−2 along with excellent operation durability. The excellent catalytic activity in acid is also verified by H2/O2 fuel cell tests (peak power density of 705 mW cm−2).
A metalorganic gaseous doping approach for constructing nitrogen‐doped carbon polyhedron catalysts embedded with single Fe atoms is reported. The resulting catalysts are characterized using scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray absorption spectroscopy; for the optimal sample, calculated densities of Fe–Nx sites and active N sites reach 1.75812 × 1013 and 1.93693 × 1014 sites cm‐2, respectively. Its oxygen reduction reaction half‐wave potential (0.864 V) is 50 mV higher than that of 20 wt% Pt/C catalyst in an alkaline medium and comparable to the latter (0.78 V vs 0.84 V) in an acidic medium, along with outstanding durability. More importantly, when used as a hydrogen–oxygen polymer electrolyte membrane fuel cell (PEMFC) cathode catalyst with a catalyst loading as low as 1 mg cm‐2 (compared with a conventional loading of 4 mg cm‐2), it exhibits a current density of 1100 mA cm‐2 at 0.6 V and 637 mA cm‐2 at 0.7 V, with a power density of 775 mW cm‐2, or 0.775 kW g–1 of catalyst. In a hydrogen–air PEMFC, current density reaches 650 mA cm‐2 at 0.6 V and 350 mA cm‐2 at 0.7 V, and the maximum power density is 463 mW cm‐2, which makes it a promising candidate for cathode catalyst toward high‐performance PEMFCs.
Highly stable and
efficient oxygen electrocatalyst with low cost
is of prime significance for fuel cells. Herein, we report hierarchical
tubular assembly of metal nitride nanosheets via a facile hydrothermal
method followed by nitridizing titanium-based dioxides. The resultant
Ti0.8Co0.2N nanosheets assembly demonstrates
considerable oxygen reduction activities in both acidic H2–air and alkaline Zn–air fuel cells. We intend to ascribe
the high performance to the integration of modified electronic effect
caused by the doping of cobalt, the high surface area and unique mesoporous
structure induced by its nanosheet assemblies, and inherent structural
stability of interlaced nitride nanosheets. This work offers an effective
approach for rational design and scalable preparation of binary nitride
nanostructures as well as a stable and efficient alternative electrocatalyst
that represents a key step toward low-cost catalysis and energy conversion.
Developing
efficient non-precious-metal catalysts to accelerate
the sluggish oxygen reduction reaction (ORR) is highly desired but
remains a great challenge. Herein, using 2D bimetallic Zn/Fe-MOF as
the precursor and g-C3N4 as the nitrogen source
and stabilizer, porous carbon nanosheets doped with large amounts
of single/paired Fe atoms (3.89 wt %) and N (10.28 wt %)
are successfully prepared. It is found that the addition of g-C3N4 plays a key role in achieving a high loading
of Fe single/paired atoms, and the 2D nanosheet structure gives the
materials a high surface area and highly porous structure, resulting
in outstanding ORR catalytic activity in both alkaline and acidic
solutions. Our optimal sample achieved half-wave potentials in alkaline
and acid media of up to 0.86 and 0.79 V (vs reversible hydrogen electrode
(RHE)), respectively, values 20 mV higher than a commercial Pt/C catalyst
in an alkaline medium and only 60 mV lower than Pt/C in an acidic
medium. Moreover, its ORR durability was superior to that of commercial
Pt/C in both electrolytes. We found that almost all the doped Fe in
the sample existed as single or paired atoms coordinated with N. This
work may provide an effective strategy for preparing high-performance
catalysts bearing single/paired atoms by using MOFs as precursors.
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