Fabrication of Fe-doped Co2P nanoparticles as efficient electrocatalyst for electrochemical and photoelectrochemical water oxidation

A Review of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) have emerged as a class of materials for the oxygen evolution reaction (OER). Because of their high earth abundance, electrical conductivity, and OER performance, these electrocatalysts have the potential to enable the practical application of green energy conversion and storage. Under OER potentials, X-ide electrocatalysts demonstrate various degrees of oxidation resistance due to their differences in chemical composition, crystal structure, and morphology. Depending on their resistance to oxidation, these catalysts will fall into one of three post-OER electrocatalyst categories: fully oxidized oxide/(oxy)hydroxide material, partially oxidized core@shell structure, and unoxidized material. In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Previous review papers have provided limited conclusions and have omitted the significance of "catalytically active sites/species/phases" in X-ide OER electrocatalysts. In this review, a comprehensive summary of (i) experimental parameters (e.g., substrates, electrocatalyst loading amounts, geometric overpotentials, Tafel slopes, etc.) and (ii) electrochemical stability tests and post-analyses in X-ide OER electrocatalyst publications from 2013 to 2022 is provided. Both mono and polyanion X-ides are discussed and classified with respect to their material transformation during the OER. Special analytical techniques employed to study X-ide reconstruction are also evaluated. Additionally, future challenges and questions yet to be answered are provided in each section. This review aims to provide researchers with a toolkit to approach X-ide OER electrocatalyst research and to showcase necessary avenues for future investigation.

Hierarchical Highly Wrinkled Trimetallic NiFeCu Phosphide Nanosheets on Nanodendrite Ni3S2/Ni Foam as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

The sluggish oxygen evolution reaction (OER) and costly noble-metal oxide catalysts hinder the vast usage of environmentally friendly water splitting for hydrogen production. Elemental doping by partial replacing of parent metal elements with elements of higher electronegativity is considered to be one of the most efficient strategies to promote the electrocatalytic OER performance. In this work, we synthesize an efficient hierarchical highly wrinkled NiFeCu phosphide nanosheet on nanodendrite Ni₃S₂/NiF substrates through partial replacement of Cu instead of Ni and Fe in NiFeP@Ni₃S₂/NiF by using a facile electrodeposition method. The NiFeCuP@Ni₃S₂/NiF electrocatalyst needs only 230, 282, and 351 mV to reach 10, 50, and 100 mA × cm^-2, respectively. Notably, this electrocatalyst shows one of the lowest OER overpotentials at 10 mA/cm^-2 for metal phosphides and endured the OER at 20 mA × cm^-2 for 18 h with negligible voltage elevation. The X-ray photoelectron spectroscopy (XPS), double-layer capacitance (C_dl) plots, and electrochemical impedance spectroscopy show that the partial Cu doping in NiFeP@Ni₃S₂/NiF not only can change the electron density around Ni and Fe but also can increase the electrochemically active surface area and conductivity of electrocatalysts.