With their high catalytic activity, stability, selectivity, and 100% atom utilization, single atomic non-noble metal based materials are valuable alternatives to efficient but expensive Pt based catalysts. For efficient catalysis, single-atom catalysts must expose abundant single atomic metal active centers. Here, we report the rational design and synthesis of a Cu single-atom catalyst with high Cu content of over 20.9 wt%, made of single atomic Cu anchored into an ultrathin nitrogenated two-dimensional carbon matrix (Cu–N–C). The high Cu content was achieved by the introduction of additional N species, which can securely trap and protect the Cu atoms. During oxygen reduction, the single atomic Cu exhibited over 54 times higher mass activity than metallic Cu nanoparticles at a potential of 0.85 V versus a reversible hydrogen electrode (RHE). Furthermore, the Cu–N–C exhibited 3.2 times higher kinetic current at 0.85 V (vs. RHE), and a much lower Tafel slope (37 mV dec⁻¹), as well as better methanol/carbon monoxide tolerance and long-term stability than commercial Pt/C. Density functional theory (DFT) calculations reveal that the Cu active sites exhibit improved O–O bond stretching and favorable adsorption energies of O₂ and OOH for four-electron oxygen reduction.

Hydrogen adsorption/desorption behavior plays a key role in hydrogen evolution reaction (HER) catalysis. The HER reaction rate is a trade-off between hydrogen adsorption and desorption on the catalyst surface. Herein, we report the rational balancing of hydrogen adsorption/desorption by orbital modulation using introduced environmental electronegative carbon/nitrogen (C/N) atoms. Theoretical calculations reveal that the empty d orbitals of iridium (Ir) sites can be reduced by interactions between the environmental electronegative C/N and Ir atoms. This balances the hydrogen adsorption/desorption around the Ir sites, accelerating the related HER process. Remarkably, by anchoring a small amount of Ir nanoparticles (7.16 wt%) in nitrogenated carbon matrixes, the resulting catalyst exhibits significantly enhanced HER performance. This includs the smallest reported overpotential at 10 mA cm⁻² (4.5 mV), the highest mass activity at 10 mV (1.12 A mg_Ir⁻¹) and turnover frequency at 25 mV (4.21 H₂ s⁻¹) by far, outperforming Ir nanoparticles and commercial Pt/C.

Identification of active sites is one of the main obstacles to rational design of catalysts for diverse applications. Fundamental insight into the identification of the structure of active sites and structural contributions for catalytic performance are still lacking. Recently, X-ray absorption spectroscopy (XAS) and density functional theory (DFT) provide important tools to disclose the electronic, geometric and catalytic natures of active sites. Herein, we demonstrate the structural identification of Zn-N₂ active sites with both experimental/theoretical X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. Further DFT calculations reveal that the oxygen species activation on Zn-N₂ active sites is significantly enhanced, which can accelerate the reduction of oxygen with high selectivity, according well with the experimental results. This work highlights the identification and investigation of Zn-N₂ active sites, providing a regular principle to obtain deep insight into the nature of catalysts for various catalytic applications.

Regulating the electronic structure of catalysts is the most efficient strategy yet, despite its limitations, to improve their oxygen evolution efficiency. Instead of only adjusting the electronic structure, here we utilize ferroelectric polarization to accelerate the oxygen evolution reaction as well. This is demonstrated on a multiferroic layered perovskite Bi₅CoTi₃O₁₅ with in-situ grown BiCoO₃. Thanks to the superimposed effects of electronic regulation and ferroelectric polarization, the as-prepared multiferroic electrocatalysts are more efficient than the benchmark IrO₂ (with a final 320 mV overpotential at the current density of 10 mA cm⁻² and a 34 mV dec⁻¹ Tafel slope). This work not only demonstrates a low-cost and high-efficient OER electrocatalyst, but also provides a strategic design for multi-component electrocatalytic material systems by consideration of both spin and polarization degrees of freedom.