Hierarchical PdNi alloy nanochains coupled with Ni(OH)2 nanosheets to enhance CO-poisoning resistance for the methanol oxidation reaction.

Hybridizing Pd-based electrocatalysts with Ni-based species has been recognized as an effective pathway to enhance the catalytic performance for the methanol oxidation reaction (MOR). However, doping Ni-based species with heterogeneous valences into Pd nanocrystals still remains challenging, although heterogeneous valence Ni species may result in improved properties of Pd from different aspects. Herein, a facile one-pot synthetic method is reported to simultaneously introduce alloyed Ni0 into Pd lattices and couple hydroxy Ni2+ species with a Pd surface, generating 1D porous PdNi alloy nanochains@Ni(OH)2 nanosheet hybrids (PdNi NCs@Ni(OH)2 NSs). Borane-tert-butylamine (C4H14BN) plays the key role in realizing the formation of Ni-based species with heterogeneous valence. On one hand, it works as a reducing agent to facilitate the doping of alloyed Ni0 into the lattice of Pd nanochains. On the other hand, it raises the solution pH value and converts the remaining [Ni(CN)4]2- into Ni(OH)2 nanosheets. Each component of the PdNi NCs@Ni(OH)2 NSs plays an important role: Pd serves as the active site, alloyed Ni0 modifies the electronic structure of Pd, and Ni(OH)2 provides abundant OHads species to strengthen the anti-poisoning capability, thus greatly enhancing the activity, CO-tolerance, and durability for the MOR.

Modulating Hydroxyl-Rich Interfaces on Nickel-Copper Double Hydroxide Nanotyres to Pre-activate Alkaline Ammonia Oxidation Reactivity.

The surface hydroxyl groups of Nix Cu1-x (OH)2 play a crucial role in governing their conversion efficiency into Nix Cu1-x Ox (OH)2-x during the electro-chemical pre-activation process, thus affecting the integral ammonia oxidation reaction (AOR) reactivity. Herein, the rational design of hierarchical porous NiCu double hydroxide nanotyres (NiCu DHTs) was reported for the first time by considering hydroxyl-rich interfaces to promote pre-activation efficiency and intrinsic structural superiority (i.e., annulus, porosity) to accelerate AOR kinetics. A systematic investigation of the structure-function relationship was conducted by manipulating a series of NiCu DHs with tunable intercalations and morphologies. Remarkably, the NiCu DHTs exhibit superior AOR activity (onset potential of 1.31 V with 7.52 mA cm-2 at 1.5 V) and high ammonia sensitivity (detection limit of 9 µm), manifesting one of the best non-noble metal AOR electrocatalysts and electro-analytical electrodetectors. This work deepens the understanding of the crucial role of surface hydroxyl groups on determining the catalytic performance in alkaline medium.

High-density growth of ultrafine PdIr nanowires on graphene: reducing the graphene wrinkles and serving as efficient bifunctional electrocatalysts for water splitting.

Manipulating the space distribution states, exposed surfaces, and interfacial interactions of graphene-based nanomaterials is a key strategy for taking full advantage of graphene's characteristics. Herein, we report the in situ deposition of numerous ultrafine PdIr alloy nanowires (diameter of 1.8 nm) to predominately cover the entire surface of graphene (PdIr UNWs/WFG). The high density but low atom loading (8.6 at%) of PdIr nanowires gives rise to abundant edge atoms and a rough surface, which are beneficial for the full exposure of active sites. Meanwhile, the compact PdIr overlay provides strong surface tension to stretch the graphene wrinkles, thus averting the wrapping of active sites and ensuring structural uniformity. The PdIr UNWs/WFG are qualified as efficient and robust electrocatalysts in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), affording 10 mA cm-2 at an HER overpotential of 23 mV and 10 mA cm-2 at an OER overpotential of 290 mV, respectively. The corresponding water electrolyzer requires a cell voltage of only 1.51 V to achieve a water-splitting current density of 10 mA cm-2. This simple and novel approach for studying the coordinated form, dispersion state, and interfacial tension is promising to be a versatile method for improving the properties of graphene-based nanomaterials.