The development of neutral zinc–air batteries (ZABs) is long been impeded by the sluggish oxygen reduction reaction (ORR) derived from insufficient O2 activation and OH* blocking effect. Herein, the synthesis of a series of rare‐earth Ce single‐atom catalysts (CeNCs) is reported with enhanced spin‐state for boosting neutral ORR. Experimental analysis and theoretical calculations indicate that the unique local coordination/geometric structure reshapes the electronic configuration of Ce sites to achieve a transition from 4d104f1 to 4d84f3. The high‐spin Ce active sites accelerate the unpaired f electrons to occupy the anti‐π orbitals of O2 and generate suitable binding strength with reaction intermediates. In neutral conditions, CeNC‐40 exhibits excellent ORR performance with half‐wave potentials of 0.78 V and negligible decay after 10 000 cycles. Additionally, the self‐breathing ZABs based on CeNC‐40 demonstrates a peak power density of 81 mW cm−2 and impressive long‐cycle stability (>1 600 cycles) at 2 mA cm−2. This work presents an effective strategy for developing high‐spin catalysts to address the challenges of neutral ZABs.
Atomically dispersed main group element single‐atom catalysts (SACs) have recently attracted increasing attention in electrocatalysis. However, their performances in acidic oxygen reduction reaction (ORR) remain unsatisfactory owing to the suboptimal coordination environment, limited mass transfer, and active site exposure. Herein, a series of p‐block Sn SACs with hierarchical pore structures are prepared by a dual melting salt‐mediated soft template method. By deliberately regulating the pore structures, highly exposed Sn active sites with N/O coordination are obtained, which endow SnN3O‐50 with exceptional ORR performances, especially in acidic medium. The half‐wave potential of SnN3O‐50 is up to 0.816 V, with a loss of only 15 mV after 10 000 potential cycles. Furthermore, the peak power densities of the fuel cell and zinc–air battery assembled using SnN3O‐50 as cathodes reach 502 and 173.5 mW cm−2, respectively, demonstrating great potential for practical applications. Density functional theory (DFT) calculations reveal that the N/O coordination of Sn induces localization of 5p electrons, which leads to strong coupling with the p orbit of O2. Meanwhile, the presence of defects synergistically regulates the adsorption of reaction intermediates, thereby optimizing the free energy of the four successive ORR steps.
Direct formic acid fuel cells (DFAFCs) are considered
promising
sustainable power sources due to their high energy density, nonflammability,
and low fuel crossover. However, serious CO poisoning and activity
attenuation of the anodic formic acid oxidation reaction (FAOR) greatly
restrict the output and durability of DFAFCs. Inspired by the specific
relationship between the composition, type, and property of alloys,
in this work, we synthesize a series of hybrid substitutional/interstitial
quaternary alloys P-PdAuAg by means of a novel polyphosphide route
to address these issues. Due to the simultaneous interstitial P-doping
and metal (Au, Ag, Pd) co-reduction, the P-PdAuAg quaternary alloy
obtained is only 3 nm in diameter with abundant defects. It not only
achieves a new high mass activity of 8.08 A mgPd
–1 (6.78 A mgcatalyst
–1) but also maintains
high stability in the high potential range and harsh reaction conditions.
Both the activity and anti-poisoning ability are far exceeding those
of the currently reported FAOR catalysts. Detailed density functional
theory (DFT) calculations reveal that the superb electrochemical performances
originate from the shift of the d-band center of Pd as a result of
the synergistic electronic/ligand effects between Pd, Au, Ag, and
P. The introduction of interstitial P inhibits the occurrence of an
indirect reaction pathway on Pd, while Au and Ag suppress the adsorption
of CO and optimize the sequential dehydrogenation steps, leading to
boosted reaction kinetics and CO tolerance. This work pioneered a
facile way for the synthesis of Pd-based substitutional/interstitial
hybrid alloys, providing a promising means of further improving the
performance of alloying catalysts.
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