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The development of highly active and stable oxygen evolution reaction (OER) electrocatalysts is crucial for improving the efficiency of water splitting and metal-air battery devices. Herein, an efficient strategy is demonstrated for making the oxygen vacancies dominated cobalt-nickel sulfide interface porous nanowires (NiS /CoS -O NWs) for boosting OER catalysis through in situ electrochemical reaction of NiS /CoS interface NWs. Because of the abundant oxygen vacancies and interface porous nanowires structure, they can catalyze the OER efficiently with a low overpotential of 235 mV at j = 10 mA cm and remarkable long-term stability in 1.0 m KOH. The home-made rechargeable portable Zn-air batteries by using NiS /CoS -O NWs as the air-cathode display a very high open-circuit voltage of 1.49 V, which can maintain for more than 30 h. Most importantly, a highly efficient self-driven water splitting device is designed with NiS /CoS -O NWs as both anode and cathode, powered by two-series-connected NiS /CoS -O NWs-based portable Zn-air batteries. The present work opens a new way for designing oxygen vacancies dominated interface nanowires as highly efficient multifunctional electrocatalysts for electrochemical reactions and renewable energy devices.

The development of active and durable bifunctional electrocatalysts for overall water splitting is mandatory for renewable energy conversion. This study reports a general method for controllable synthesis of a class of IrM (M = Co, Ni, CoNi) multimetallic porous hollow nanocrystals (PHNCs), through etching Ir-based, multimetallic, solid nanocrystals using Fe ions, as catalysts for boosting overall water splitting. The Ir-based multimetallic PHNCs show transition-metal-dependent bifunctional electrocatalytic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acidic electrolyte, with IrCo and IrCoNi PHNCs being the best for HER and OER, respectively. First-principles calculations reveal a ligand effect, induced by alloying Ir with 3d transition metals, can weaken the adsorption energy of oxygen intermediates, which is the key to realizing much-enhanced OER activity. The IrCoNi PHNCs are highly efficient in overall-water-splitting catalysis by showing a low cell voltage of only 1.56 V at a current density of 2 mA cm , and only 8 mV of polarization-curve shift after a 1000-cycle durability test in 0.5 m H SO solution. This work highlights a potentially powerful strategy toward the general synthesis of novel, multimetallic, PHNCs as highly active and durable bifunctional electrocatalysts for high-performance electrochemical overall-water-splitting devices.

The grand challenge in the development of atomically dispersed metallic catalysts is their low metal-atom loading density, uncontrollable localization and ambiguous interactions with supports, posing difficulty in maximizing their catalytic performance. Here, we achieve an interface catalyst consisting of atomic cobalt array covalently bound to distorted 1T MoS2 nanosheets (SA Co-D 1T MoS2). The phase of MoS2 transforming from 2H to D-1T, induced by strain from lattice mismatch and formation of Co-S covalent bond between Co and MoS2 during the assembly, is found to be essential to form the highly active single-atom array catalyst. SA Co-D 1T MoS2 achieves Pt-like activity toward HER and high long-term stability. Active-site blocking experiment together with density functional theory (DFT) calculations reveal that the superior catalytic behaviour is associated with an ensemble effect via the synergy of Co adatom and S of the D-1T MoS2 support by tuning hydrogen binding mode at the interface.

The development of highly efficient bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for improving the efficiency of the Zn-air battery. Herein, we report porous NiO/CoN interface nanowire arrays (PINWs) with both oxygen vacancies and a strongly interconnected nanointerface between NiO and CoN domains for promoting the electrocatalytic performance and stability for OER and ORR. Extended X-ray absorption fine structure spectroscopy, electron spin resonance, and high-resolution transmission electron microscopy investigations demonstrate that the decrease of the coordination number for cobalt, the enhanced oxygen vacancies on the NiO/CoN nanointerface, and strongly coupled nanointerface between NiO and CoN domains are responsible for the good bifunctional electrocatalytic performance of NiO/CoN PINWs. The primary Zn-air batteries, using NiO/CoN PINWs as an air-cathode, display an open-circuit potential of 1.46 V, a high power density of 79.6 mW cm, and an energy density of 945 Wh kg. The three-series solid batteries fabricated by NiO/CoN PINWs can support a timer to work for more than 12 h. This work demonstrates the importance of interface coupling and oxygen vacancies in the development of high-performance Zn-air batteries.