Guohua Li,Meitong Zhao,Fan Yang,Hongchen Liu,Jing Wang,Jintian Ren,Yongfeng Li
Designing small size well-dispersed transition metal phosphides nanoparticles with more exposed catalytic sites and strong interfacial coupling properties is an efficient method for optimizing water splitting performance. Herein, various adjustable sizes of CoP/CoNiP nanoparticles securely anchored on asphalt-derived porous carbon (labeled as Co x Ni 1-x P/C) are successfully constructed by using preferred ethanol/water solvent. The as-obtained optimal 6-8 nm-sized Co 0.67 Ni 0.33 P/C achieves cutting-edge catalytic performance than the counterparts with an overpotential of 58 mV for hydrogen evolution reaction and 231 mV for oxygen evolution reaction at 10 mA cm −2 in 1.0 M KOH. Importantly, it requires an overpotential of 225 mV@500 mA cm −2 for HER superior to that of commercial Pt/C. Meanwhile, Co 0.67 Ni 0.33 P/C represents outstanding stability as proved by almost perfectly overlapping curves of current density in the long-time voltage cycles (3000 cycles) and negligible degradation after chronopotentiometry tests (up to 24 h) under 10 mA cm −2 . In catalyzing overall water splitting, just 1.59 V is obtained to accomplish 10 mA cm −2 using Co 0.67 Ni 0.33 P/C as both electrodes, surpassing most advanced bifunctional catalysts. By this research, we introduce an efficient synthetic strategy for creating carbon-based transition metal phosphides with small particle size and remarkable catalytic activity in new ways.
Xiaoyan Wang,Ying Xie,Wei Zhou,Xiuwen Wang,Zhicheng Cai,Zipeng Xing,Mingxia Li,Kai Pan
The hierarchical electrocatalysts with the superaerophobic property are in favor of removal of gas bubbles and supply of numerous active sites to improve the electrochemical catalytic activity for water splitting. In this work, the self-supported Zn-doped CoNiP (Zn–CoNiP/NF) hierarchical structure that consisted of nanothorns and radial microspheres were prepared with via a facile precursor phosphorization method. Zn-doping could tailor the initial electronic state of CoNiP to improve the hydrogen or oxygen atom binding, which effectively promoted the catalytic kinetics of water splitting. The hierarchical structure not only offered more catalytic active sites for water splitting, but also facilitated gas releasing due to the superaerophobic interface. The hierarchical Zn–CoNiP structure showed a high hydrogen evolution reaction (HER) efficiency in electrolytes with pH 0–14, which yielded low overpotentials of 73 mV in acidic solution and 34 mV in alkaline media at current density of 10 mA cm −2 . Furthermore, it also had evidenced by an overpotential of 310 mV for oxygen evolution reaction (OER) at the current density of 50 mA cm −2 . Note that the required cell initial voltage was 1.51 V for overall water splitting. These results were comparable or even better than many non-noble catalysts.
As a safe and efficient hydrogen storage material, ammonia borane (NH3–BH3, AB) shows great promise in the era of clean energy advocated by hydrogen. Thus, it is imperative to focus on the exploitation of high-performance heterogeneous catalytic systems for the effective utilization of hydrogen energy stored in AB. However, noble metal catalysts as high-efficiency systems suffer from high expenditure, and the traditional powder-based catalyst faces poor processability and recoverability. Herein, a bimetallic (Co/Ni) MOF-derived CoNiP/hierarchically porous carbon (HPC) monolithic aerogel was successfully prepared by the gelation–carbonization–phosphorization method and applied in the hydrolysis of AB. The ultrasmall transition bimetallic phosphide CoNiP nanoparticles were uniformly fabricated in the hierarchically porous aerogel after pyrolysis. Benefiting from the rapid mass transfer and high exposure of well-defined CoNiP-active species within the hierarchical aerogel support, the Co0.3Ni0.7P/HPC aerogel performed high hydrogen evolution activity and exhibited fast hydrogen generation rate with a completion time of 2 min under mild conditions. The theoretical calculations reveal the key effects of the adsorption energies between AB and water on CoNiP-active sites in the Co0.3Ni0.7P/HPC aerogel. Furthermore, the Co0.3Ni0.7P/HPC monolithic aerogel catalyst can be effortlessly separated and recycled at least 10 times without a remarkable loss of activity. The controllable design of P-doped bimetallic species in the porous aerogel herein should serve as the foundation for the preparation of practical functional monolithic applied catalysts for the hydrolysis of AB.
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