Co3Mo3N-An efficient multifunctional electrocatalyst.

Efficient catalysts are required for both oxidative and reductive reactions of hydrogen and oxygen in sustainable energy conversion devices. However, current precious metal-based electrocatalysts do not perform well across the full range of reactions and reported multifunctional catalysts are all complex hybrids. Here, we show that single-phase porous Co3Mo3N prepared via a facile method is an efficient and reliable electrocatalyst for three essential energy conversion reactions; oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) in alkaline solutions. Co3Mo3N presents outstanding OER, ORR, and HER activity with high durability, comparable with the commercial catalysts RuO2 for OER and Pt/C for ORR and HER. In practical demonstrations, Co3Mo3N gives high specific capacity (850 mA h gZn -1 at 10 mA cm-2) as the cathode in a zinc-air battery, and a low potential (1.63 V at 10 mA cm-2) used in a water-splitting electrolyzer. Availability of Co and Mo d-states appear to result in high ORR and HER performance, while the OER properties result from a cobalt oxide-rich activation surface layer. Our findings will inspire further development of bimetallic nitrides as cost-effective and versatile multifunctional catalysts that will enable scalable usage of electrochemical energy devices.

Intrinsic Electron Localization of Metastable MoS2 Boosts Electrocatalytic Nitrogen Reduction to Ammonia.

The advancement of efficient electrocatalysts toward the nitrogen reduction reaction (NRR) is critical in sustainable ammonia synthesis under ambient pressure and temperature. Manipulating the electronic configuration of electrocatalysts is particularly vital to form metal-nitrogen (MN) bonds during the NRR through regulating the active electronic states of sites. Here, in sharp contrast to stable 2H MoS2 without metal chains, MoMo bonding in metastable polymorphs of MoS2 bulk (zigzag chain in the 1T' phase and diamond chain in the 1T″' phase) is discovered to significantly increase intrinsic electron localization around the metal chains. This can enhance the charge transfer from the adsorbed nitrogen molecule to the metal chains, allowing for boosted NRR kinetics. The electrochemical experiments show that the NH3 yield rate and the faradaic efficiency of the metastable 1T″' MoS2 rich with abundant Mo-Mo bonds are about 9 and 12 times above average than those of 2H MoS2 , correspondingly. Theoretical simulations reveal the high local electron density surrounding the MoMo chains and sites can promote π back-donation, which is beneficial for increasing nitrogen adsorption, strengthening the MN bonds, and reducing the cleavage barrier of the triple NN bond.

Titanium Nitride-Supported Platinum with Metal-Support Interaction for Boosting Photocatalytic H2 Evolution of Indium Sulfide.

Metal-support interaction strongly influences the catalytic properties of metal-based catalysts. Here, titanium nitride (TiN) nanospheres are shown to be an outstanding support, for tuning the electronic property of platinum (Pt) nanoparticles and adjusting the morphology of indium sulfide (In2S3) active components, forming flower-like core-shell nanostructures (TiN-Pt@In2S3). The strong metal-support interaction between Pt and TiN through the formation of Pt-Ti bonds favors the migration of charge carriers and leads to the easy reducibility of TiN-Pt, thus improving the photocatalytic atom efficiency of Pt. The TiN-Pt@In2S3 composite shows reduction of Pt loading by 70% compared to the optimal Pt-based system. In addition, the optimal TiN-Pt@In2S3 composite exhibits a H2 evolution rate 4 times that of a Pt reference. This increase outperforms all other supports reported thus far.

A Surface-Oxide-Rich Activation Layer (SOAL) on Ni2 Mo3 N for a Rapid and Durable Oxygen Evolution Reaction.

The oxygen evolution reaction (OER) is key to renewable energy technologies such as water electrolysis and metal-air batteries. However, the multiple steps associated with proton-coupled electron transfer result in sluggish OER kinetics and catalysts are required. Here we demonstrate that a novel nitride, Ni2 Mo3 N, is a highly active OER catalyst that outperforms the benchmark material RuO2 . Ni2 Mo3 N exhibits a current density of 10 mA cm-2 at a nominal overpotential of 270 mV in 0.1 m KOH with outstanding catalytic cyclability and durability. Structural characterization and computational studies reveal that the excellent activity stems from the formation of a surface-oxide-rich activation layer (SOAL). Secondary Mo atoms on the surface act as electron pumps that stabilize oxygen-containing species and facilitate the continuity of the reactions. This discovery will stimulate the further development of ternary nitrides with oxide surface layers as efficient OER catalysts for electrochemical energy devices.

A size tunable bimetallic nickel-zinc nitride as a multi-functional co-catalyst on nitrogen doped titania boosts solar energy conversion.

To enable high-efficiency solar energy conversion, rational design and preparation of low cost and stable semiconductor photocatalysts with associated co-catalysts are desirable. However preparation of efficient catalytic systems remains a challenge. Here, N-doped TiO2/ternary nickel-zinc nitride (N-TiO2-Ni3ZnN) nanocomposites have been shown to be a multi-functional catalyst for photocatalytic reactions. The particle size of Ni3ZnN can be readily tuned using N-TiO2 nanospheres as the active support. Due to its high conductivity and Pt-like properties, Ni3ZnN promotes charge separation and transfer, as well as reaction kinetics. The material shows co-catalytic performance relevant for multiple reactions, demonstrating its multifunctionality. Density functional theory (DFT) based calculations confirm the intrinsic metallic properties of Ni3ZnN. N-TiO2-Ni3ZnN exhibits evidently improved photocatalytic performances as compared to N-TiO2 under visible light irradiation.

Zirconium nitride catalysts surpass platinum for oxygen reduction.

Platinum (Pt)-based materials are important components of microelectronic sensors, anticancer drugs, automotive catalytic converters and electrochemical energy conversion devices1. Pt is currently the most common catalyst used for the oxygen reduction reaction (ORR) in devices such as fuel cells and metal-air batteries2,3, although a scalable use is restricted by the scarcity, cost and vulnerability to poisoning of Pt (refs 4-6). Here we show that nanoparticulate zirconium nitride (ZrN) can replace and even surpass Pt as a catalyst for ORR in alkaline environments. As-synthesized ZrN nanoparticles (NPs) exhibit a high oxygen reduction performance with the same activity as that of a widely used Pt-on-carbon (Pt/C) commercial catalyst. Both materials show the same half-wave potential (E1/2 = 0.80 V) and ZrN has a higher stability (ΔE1/2 = -3 mV) than the Pt/C catalyst (ΔE1/2 = -39 mV) after 1,000 ORR cycles in 0.1 M KOH. ZrN is also shown to deliver a greater power density and cyclability than Pt/C in a zinc-air battery. Replacement of Pt by ZrN is likely to reduce costs and promote the usage of electrochemical energy devices, and ZrN may also be useful in other catalytic systems.