Design and synthesis Zn doped CoP/Co2P nanowire arrays for boosting hydrogen generation reaction

Abstract

Element doping is an effective method to improve the performance of noble-metal-free catalysts. Herein, Zn doped CoP/Co2P nanowire arrays on carbon cloth (CC) are synthesized via a two-step strategy. The two-steps involve the Zn doped Co(OH)F nanowire arrays are grown on the CC, and the conversion of Co(OH)F to CoP/Co2P. The conversion of Co(OH)F to CoP/Co2P can produce large number of porous. The porous structure provides abundant edge sites and more electroactive surface directly exposed to the electrolyte, leading to effectively improve the activity of the catalyst for hydrogen evolution reactions (HER). The doping of Zn element can create electronic defects, modulate the electronic structure, reduce hydrogen adsorption free energy and consequently enhance electrocatalytic performance of catalysts. Moreover, the ratio of doped Zn in the product also affects significantly the HER activities of CoP/Co2P@CC, minor-doping and over-doping is unfavorable to the improvement of catalyst performance. As a result, compare with pure CoP/Co2P@CC, the Zn0.64-CoP/Co2P@CC (which is obtained at the optimal ratio) exhibits better catalytic performance for HER in both acid and alkaline media. The overpotential of HER is as low as 81 ​mV in 0.5 ​M ​H2SO4 and 95 ​mV in 1 ​M KOH at a current density of 10 ​mA ​cm−2, respectively, which are nearly two times lower than the pure CoP/Co2P@CC. Correspondingly, the Tafel slope of the electrode reaction is as low as 69 ​mV dec−1 and 87 ​mV dec−1 in acid and alkaline solution, respectively. This study demonstrates that nontoxic Zn element can be used as an effective dopant to increase the activity of the catalysts, so as to provide some guidelines for fabricating other materials with excellent performances for energy storage and conversion devices.