Facile Preparation of Amorphous Fe–Co–Ni Hydroxide Arrays: A Highly Efficient Integrated Electrode for Water Oxidation

Grain Boundary Effects of Hierarchical Ni-Fe (Oxy)hydroxide Nanosheets in Water Oxidation

The robust and scalable oxygen evolution electrocatalysts that can deliver high current densities at low applied potential is a great challenge for the large-scale industrial application in hydrogen production. Here, the preparation of a grain-boundary-rich Ni-Fe (oxy)hydroxide catalyst on Ni foam is reported using a scalable coating approach followed by a chemical precipitating treatment. This facile method effectively assembles the hierarchical Ni-Fe (oxy)hydroxide nanosheet in the ultrasmall crystalline domains (<4 nm) with rich grain boundaries. The hierarchical nanosheet structure with the grain boundaries provides more accessible catalytic sites, facile charge, and mass transfer. Benefiting from the abundant grain boundaries in the hierarchical nanosheets, the as-prepared Ni-Fe (oxy)hydroxide electrodes deliver current densities of 500 and 1000 mA cm-2 at overpotentials of only 278 and 296 mV for the oxygen evolution reaction. The prepared electrode also exhibits long-term durability at a high current density in alkaline conditions.

Construction of Non-Precious Metal Self-Supported Electrocatalysts for Oxygen Evolution from a Low-Temperature Immersion Perspective

Water splitting is considered as a promising technology to solve energy shortage and environmental pollution. Since oxygen evolution reaction (OER) directly affects the efficiency of hydrogen evolution, the preparation of efficient and inexpensive OER catalysts is an urgent problem. "Low-temperature immersion" (LTI) is expected to be a prospective strategy for electrocatalyst preparation due to its simplicity and energy-saving advantages. However, there is almost no comprehensive overview on the progress of LTI engineering in the construction of non-precious metal self-supported electrocatalysts for OER. Herein, this review firstly introduces the principles and applications of LTI engineering-assisted preparation of non-precious metal self-supported electrocatalysts in terms of etching and deposition. Then the mechanism of OER is analyzed from an amorphous viewpoint, and finally some perspective insights and future challenges of this method are discussed.

Fe Engineering on Ru Nanosheets for Enhanced Hydrogen Evolution in pH-Universal Media

Fe-modified Ru nanosheets are achieved via preintercalated Al species serving as the self-sacrificial template. Benefiting from the amphoteric feature of Al and strong corrosion of Fe³⁺ ions, Fe is effectively incorporated into pristine Ru nanosheets. Correspondingly, the surface oxophilicity is improved, promoting the Volmer step. The charge density redistribution weakens hydrogen combination on Ru and thus accelerates the desorption kinetics (Heyrovsky step). Meanwhile, more defective sites are exposed, leading to an enhanced hydrogen production in pH-universal electrolytes.

Fabrication of a porous NiFeP/Ni electrode for highly efficient hydrazine oxidation boosted H2 evolution

Rational optimization of the surface electronic states and physical structures of non-noble metal nanomaterials is essential to improve their electrocatalytic performance. Herein, we report a facile dual-regulation strategy to fabricate NiFeP/Ni (P-NiFeP/Ni) porous nanoflowers, which involves Fe-doping and creating pores on nanosheets. The as-prepared P-NiFeP/Ni has a hierarchically porous surface, which exposes more electrochemically active sites and dramatically enhances the electron transfer rate. Thus, it exhibits excellent catalytic activity in both anodic hydrazine oxidation reaction (HzOR) and cathodic hydrogen evolution reaction (HER). Interestingly, the coupled electrolysis cell only offers a potential of 0.162 V at 10 mA cm^-2 to enable HzOR boosted H₂ evolution, highlighting an energy-saving hydrogen evolution strategy.