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Minimizing precious metal loading into electrocatalysts for water splitting is vital to promoting hydrogen energy technology toward practical applications. Low-content loading of precious-metal electrocatalysts is achieved by decorating precious metal nanostructures on co-electrocatalysts typically via surface confinement. Here, an electrocatalyst of ultralow-content Pt nanodots (0.71 wt%)/Ni 3 Fe nanoparticles on reduced oxidation graphene (Pt/Ni 3 Fe/rGO) is constructed for overall water splitting by pyrolyzing a single-source precursor PtCl 6 3- guest-intercalated MgNiFe-layered double hydroxide (MgNiFe-LDH) host via a distinctive interlayer confinement. Consequently, Pt/Ni 3 Fe/rGO demonstrates attractive overpotentials of 240 and 76 mV at 10 mA cm -2 for the oxygen and hydrogen evolution reactions (OER and HER), respectively, outperforming those of its /Ni 3 Fe/rGO counterpart. Moreover, the Pt/Ni 3 Fe/rGO∥Pt/Ni 3 Fe/rGO electrolyzer generates a current density of 10 mA cm -2 at 1.55 V, with a retention of 92.4% after 50 h. Furthermore, the measured specific activity and low transfer resistance, as well as the density functional theory (DFT) calculations, indicate that the active Pt/Ni 3 Fe in Pt/Ni 3 Fe/rGO can optimize the adsorption/desorption of reaction intermediates and thus boost OER/HER kinetics, all of which lead to enhanced performance. The results demonstrate that such an interlayer confinement-based synthesis strategy can allow for the design of cost-effective precious nanodots as potential electrocatalysts.

O3-type layered oxide cathodes (Na x TMO 2 ) for sodium-ion batteries (SIBs) have attracted significant attention as one of the most promising potential candidates for practical energy storage applications. The poor Na + diffusion kinetics is, however, one of the major obstacles to advancing large-scale practical application. Herein, we report bismuth-doped O3-NaNi 0.5 Mn 0.5 O 2 (NMB) microspheres consisting of unique primary nanoplatelets with the radially oriented {010} active lattice facets. The NMB combines the advantages of the oriented and exposed electrochemical active planes for direct paths of Na + diffusion, and the thick primary nanoplatelets for less surface parasitic reactions with the electrolyte. Consequently, the NMB cathode exhibits a long-term stability with an excellent capacity retention of 72.5% at 1 C after 300 cycles and an enhanced rate capability at a 0.1 C to 10 C rate (1 C = 240 mA g -1 ). Furthermore, the enhancement is elucidated by the small volume change, thin cathode-electrolyte-interphase (CEI) layer, and rapid Na + diffusion kinetics. In particular, the radial orientation-based Bi-doping strategy is demonstrated to be effective at boosting electrochemical performance in other layered oxides (such as Bi-doped NaNi 0.45 Mn 0.45 Ti 0.1 O 2 and NaNi 1/3 Fe 1/3 Mn 1/3 O 2 ). The results provide a promising strategy of utilizing the advantages of the oriented active facets of primary platelets and secondary particles to develop high-rate layered oxide cathodes for SIBs.