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Electrocatalytic water oxidation is a rate-determining step in the water splitting reaction. Here, we report one single atom W 6+ doped Ni(OH) 2 nanosheet sample (w-Ni(OH) 2 ) with an outstanding oxygen evolution reaction (OER) performance that is, in a 1 M KOH medium, an overpotential of 237 mV is obtained reaching a current density of 10 mA/cm 2 . Moreover, at high current density of 80 mA/cm 2 , the overpotential value is 267 mV. The corresponding Tafel slope is measured to be 33 mV/dec. The d 0 W 6+ atom with a low spin-state has more outermost vacant orbitals, resulting in more water and OH − groups being adsorbed on the exposed W sites of the Ni(OH) 2 nanosheet. Density functional theory (DFT) calculations confirm that the O radical and O-O coupling are both generated at the same site of W 6+ . This work demonstrates that W 6+ doping can promote the electrocatalytic water oxidation activity of Ni(OH) 2 with the highest performance.

Identification of catalytic sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in carbon materials remains a great challenge. Here, we construct a pyridinic-N-dominated doped graphene with abundant vacancy defects. The optimized sample with an ultrahigh pore volume (3.43 cm3 g–1) exhibits unprecedented ORR activity with a half-wave potential of 0.85 V in alkaline. For the first time, density functional theory results indicate that the quadri-pyridinic N-doped carbon site synergized with a vacancy defect is the active site, which presents the lowest overpotential of 0.28 V for ORR and 0.28 V for OER. The primary Zn–air batteries display a maximum power density of 115.2 mW cm–2 and an energy density as high as 872.3 Wh kg–1. The rechargeable Zn–air batteries illustrate a low discharge–charge overpotential and high stability (>78 h). This work provides new insight into the correlation between the N configuration synergized with a vacancy defect in electrocatalysis.

Exploring new materials is essential in the field of material science. Especially, searching for optimal materials with utmost atomic utilization, ideal activities and desirable stability for catalytic applications requires smart design of materials’ structures. Herein, we report iridium metallene oxide: 1 T phase-iridium dioxide (IrO2) by a synthetic strategy combining mechanochemistry and thermal treatment in a strong alkaline medium. This material demonstrates high activity for oxygen evolution reaction with a low overpotential of 197 millivolt in acidic electrolyte at 10 milliamperes per geometric square centimeter (mA cmgeo−2). Together, it achieves high turnover frequencies of 4.2 sUPD−1 (3.0 sBET−1) at 1.50 V vs. reversible hydrogen electrode. Furthermore, 1T-IrO2 also shows little degradation after 126 hours chronopotentiometry measurement under the high current density of 250 mA cmgeo−2 in proton exchange membrane device. Theoretical calculations reveal that the active site of Ir in 1T-IrO2 provides an optimal free energy uphill in *OH formation, leading to the enhanced performance. The discovery of this 1T-metallene oxide material will provide new opportunities for catalysis and other applications.

The Janus structures of transition metal dichalcogenides with an intrinsic dipole have been proposed as efficient photocatalysts for water splitting, and successfully synthesized recently. However, the mechanism for their superior photocatalytic activities are not understood. Here, we systematically investigate the photocatalytic activities of Janus molybdenum dichalcogenides (MoXY, X/Y = O, S, Se, and Te), by studying their band gaps, redox energy levels and electrons and holes separation, by first-principles calculations. The intrinsic dipoles in the Janus structures cause notable band bending to achieve favorable band edge positions relative to water redox potentials, which makes the Janus structures as efficient heterojunction photocatalysts. Electrons and holes are spatially separated on different surfaces of the Janus structure due to the internal electric field, which effectively inhibits the recombination of excitons and ensures photocatalytic activity with high efficiency.