The design and preparation of high-efficiency and durable non-precious metal electrocatalysts are critical to the realization of large-scale water splitting. In this work, nano cubic clusters of Ni and Fe bimetallic phosphides (NiFeP@NC/NF) grown on NF substrates were synthesized through a simple secondary hydrothermal reaction and low-temperature phosphating. By exploring the phosphating temperature, the optimized NiFeP@NC/NF material shows excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) properties in 1.0 M KOH electrolyte. It has a small initial overpotential of 286 and 242 mV and low Tafel slope of 69 and 126 mV dec −1 at current density of 20 mA cm −2 , which is attributed to the synergistic effect of NC@ NiFeP nanocubic clusters and NF framework, NiFeP@NC nanocubic clusters not only provide more active specific surface area but also the interlaced structure is more stable. The introduction of miscellaneous elements can accelerate the mass transfer in the reaction. The results show that NiFeP@NC/NF is an excellent dual-function electrocatalyst for water splitting and a promising candidate for electrocatalytic water splitting.
Guyang Ning,Mingxuan Fu,Jiaxian Liu,Yuena Sun,Haijun Lu,Haiyang Wang,Xinyu Fan,Yufan Zhang,Huan Wang
Transition metal catalysts were supposed to be the most likely substitute for commercial noble metal catalysts, and the development of highly active and long-term catalyst for water splitting are the future trend. Herein, Ni rectangular nitrogen doped carbon nanorods@Fe–Co nanocubes (Ni-CNRs@Fe–Co cubes) were fabricated via a facile template-free method. This simple strategy not only realizes the structure tailoring, but also achieves high-quality nitrogen-doping. Specifically, nickel dimethylglyoxime [Ni(dmg) 2 ] with rectangular rodlike structure was firstly synthesized by solution method, then metal-organic frameworks Fe–Co nanocube with different contents were loaded on rectangular carbon nanorods with polydopamine as the locating and the connecting agent, and finally Ni-CNRs@xFe-Co cubes were obtained by a one-step calcination . A series of electrochemical tests were researched on materials with different metal contents in the 1 M KOH solution. The Ni-CNRs@Fe–Co cubes show excellent electrocatalytic activity in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). For HER and OER, the Tafel slopes were 83.3 mV dec −1 and 71 mV dec −1 , the onset potential were −167 mV and 1.62 V, and reached the current densities of 10 mA cm −2 , the overpotential just needed 196 mV and 433 mV, respectively. This novel synthetic strategy will provide a template-free way for cheap electrocatalysts of non-precious metal for OER and HER.
Ni2−xCoxP (0 ≤ x ≤ 2) nanocrystals (NCs) with good control of composition are synthesized by a facile economical approach. Low-cost air-stable triphenylphosphine is used as phosphorus source and NaBH4 is added to facilitate the reaction, which helps to carry out the reaction at relatively low temperature (250 °C). By modulating the Ni/Co precursor ratios, the composition of Ni2−xCoxP NCs can be tuned over the whole range. A comprehensive study of the key role of NaBH4 on the metal phosphide NCs formation reveals that NaBH4 can efficiently activate the triphenylphosphine, lowering the thermodynamic barrier for the P–C bond broken and thus reducing the reaction temperature. As-prepared Ni2−xCoxP NCs show Ni/Co-composition dependent catalytic performance on both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In particular, OER catalytic activities follow the volcano relationship due to the synergistic effect. The Ni1.0Co1.0P NCs exhibit the highest OER catalytic activity with the overpotential of 0.34 V at a current density of 10 mA cm−2, among the top tier of water oxidation catalysts. In addition to providing a new green low-cost route to composition controllable synthesis of ternary phosphides, this work also contributes to fundamental guideline on rational design of low-cost high-efficient catalysts for water splitting.
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