Controlled synthesis of Mo and Ni codoped Co2P as environmentally friendly catalyst for urea, freshwater and seawater oxidation

Abstract

The thermodynamic equilibrium potential of urea electrolysis (0.37 V) is lower than that of conventional water electrolysis (1.23 V). In this paper, the urea oxidation reaction performance of Ni-Co2P was regulated and enhanced by doping with different quantity of Mo. The growth characteristics of Mo doping Ni-Co2P were characterized and analyzed to reveal the electrochemical properties of the target catalysts, and finally the electrochemical performance tests were carried out. The experimental results show that MoNi-Co2P-0.12 electrode exhibits superior catalytic activity and durability at an iR compensation of 90. What is noteworthy is that at a current density of 10 mA cm−2, the MoNi-Co2P-0.12 catalyst showed an ultra-low voltage of 1.244 V with a small Tafel slope (79.52 mV dec−1) and stable catalysis for over 12 h, which is one of the best catalytic activities reported to date. Experimental results show that the increased activity of the MoNi-Co2P-0.12 catalyst is attributable to synergic catalytic effect of Mo and Co, electron regulation and exposure of more active sites. Density functional theory (DFT) calculations demonstrate the doping of Mo can increase the urea adsorption energy of the MoNi-Co2P material compared with the Ni-Co2P material, and is also conducive to the improvement of the conductivity of the MoNi-Co2P material. This work provides new research into the use of cheap transition metal catalysts as an alternative to precious metal catalysts for urea electrolysis.