Pt single-atom materials possess an ideal atom economy but suffer from limited intrinsic activity and side reaction of producing H2O2 in catalyzing the oxygen reduction reaction (ORR); platinum alloys have higher intrinsic activity but weak stability. Here, we demonstrate that anchoring platinum alloys on single-atom Pt-decorated carbon (Pt-SAC) surmounts their inherent deficiencies, thereby enabling a complete four-electron ORR pathway catalysis with high efficiency and durability. Pt3Co@Pt-SAC demonstrates an exceptional mass and specific activities 1 order of magnitude higher than those of commercial Pt/C. They are durable throughout 50000 cycles, showing only a 10 mV decay in half-wave potential. An in situ Raman analysis and theoretical calculations reveal that Pt3Co core nanocrystals modulate electron structures of the adjacent Pt single atoms to facilitate the intermediate absorption for fast kinetics. The superior durability is attributed to the shielding effect of the Pt-SAC coating, which significantly mitigates the dissolution of Pt3Co cores. The hybridizing strategy might promote the development of highly active and durable ORR catalysts.

Cost-effective electrochemical water splitting technology hinges on the development of efficient and durable catalysts for oxygen evolution reaction (OER). Spinel oxides (formula: A x B3–x O4) are structurally stable for real applications. Much effort has been devoted to improving the catalytic activity. Here, we report a eutectic dealloying strategy to activate the porous spinel NiFe2O4 nanowires with up to four metal cation substitutions. As-obtained spinel NiFeXO4 (X = Fe, Ni, Al, Mo, Co, Cr) delivers a benchmark current density of 10 mA·cm–2 at an overpotential of only 195 mV, outperforming most spinel phase OER electrocatalysts and comparable to the state-of-the-art NiFe hydroxides. It is stable for over 115 h of electrolysis. Aberration-corrected transmission electron microscopy, high-resolution electron energy loss spectroscopy, and atomic-scale strain mappings reveal that the multivalent cation substitutions result in substantial lattice distortion and significant electronic coupling of metal 3d and O 2p orbitals for increased covalency. Further theoretical calculations suggest that the NiFeXO4 are stabilized by the high configurational entropy, and their synergy favors the absorption of H2O molecules and lowers the adsorption energy barrier of the OOH* intermediate. The improved intrinsic activity together with the highly nanoporous structures contribute to the appealing apparent catalytic performances. The work demonstrates an effective approach for the synthesis of stable multicomponent spinel oxides and highlights the effectiveness of the multication substitution strategy for producing highly durable and active spinel catalysts, which meet multiplexed structure and superior property requirements in practical applications.

Oxygen vacancies (Ov) engineering has demonstrated tremendous power to expedite electrocatalytic kinetics for oxygen evolution reaction (OER). The mechanism is elusive, and most of them were attributed to the decoration or creation of active sites. Here, we report the critical role of superficial Ov in enhancing the electronic transport, thereby unfolding the catalytic potential of NiFe-layered double hydroxides for OER. We reveal that the superficial Ov engineering barely regulates the intrinsic catalytic activities but lowers the charge transport resistances by more than one order of magnitude. Loading-dependent electrochemical analysis suggests that the superficial Ov engineering intensively modulates the utilization rate of electronically accessible active sites for OER catalysis. By correlating catalytic activities to charging capacitances of C Φ (related to the absorption of reaction intermediates), we unveil a linear dependence, which indicates switchable catalysis on electronically accessible active sites. Based on the unified experimental and theoretical analysis of the electronic structures, we propose that the superficial Ov imposes electron donation to the conductive band of NiFeOOH, thereby enabling the regulation of electronic transport to switch on/off OER catalysis. The switch effect holds fundamental and technical implications for understanding and designing efficient electrocatalysts.

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Electrocatalysts for the oxygen reduction reaction (ORR) play a central role in fuel cells and zinc–air batteries. Bimetal single atoms and nanoparticle hybrids are emerging ORR electrocatalysts, superior to the most exploited unary metal single-atom catalysts (SACs). Here, we report bimetal SAC-based nanofiber networks of Co3Fe7@Co/Fe-SAC for efficient ORR electrocatalysis and zinc–air batteries. A facile and easy-to-scale-up process is developed, and the versatility is validated in three hybrids. Strong electronic interaction is revealed between bimetal single atoms and alloy nanoparticles, leading to improved catalytic performances for ORR. Specifically, the Co3Fe7@Co/Fe-SAC hybrids exhibit a half-wave potential of 0.841 V in a basic electrolyte, comparable to the Pt/C electrocatalyst. Assembled in a zinc–air battery, a Co3Fe7@Co/Fe-SAC hybrid-based cell demonstrates a power density 1.8 times higher than the benchmark Pt/C-IrO2-based one, and it is stable for 150 cycles galvanostatic charge/discharge. The superior device performance is attributed to the appealing intrinsic activity, the carbon shielding effect for anti-leaching, and the hierarchical porous networks for large accessibility of active sites and favorable mass transport. Theoretical calculations suggest that alloy nanoparticles significantly improved the intrinsic catalytic activity of Fe single-atom sites at the expense of slightly lowering the activity of Co single-atom sites. This work presents a versatile process for the mass production of efficient composite electrocatalysts and highlights the power of bimetal single-atom-based hybrids and hierarchically porous structures for ORR device performances.