Nickel Phosphide Clusters Sensitized TiO2 Nanotube Arrays as Highly Efficient Photoanode for Photoelectrocatalytic Urea Oxidation

The photoelectrocatalytic urea oxidation reaction (PEC-UOR) holds a great promise for the wastewater remediation and energy production. However, the low efficiency of semiconductor/cocatalysts type photoanodes for UOR restricts their applications in photoelectrocatalytic system. Herein, a new semiconductor/cocatalyst, Ni2P clusters sensitized TiO2 nanotube arrays photoanode (Ni2P/TiO2-NTAs) for PEC-UOR with high efficiency are developed. The 1D TiO2-NTAs structure accelerates urea molecules diffusion and promotes CO2 gas release at the electrode interface. Meanwhile, Ni2P is also beneficial to urea molecule absorption and CO2 desorption and enable to lower the energy barrier for amine (N-H) dehydrogenation. Furthermore, the robust interfacial charge transfer pathway between Ni2P and TiO2 interface promotes the separation of photogenerated electrons and holes and the transfer of photogenerated electrons from Ni2P to TiO2. Therefore, this photoanode shows excellent PEC-UOR performance with the potential of 1.43 V versus reversible hydrogen electrode (RHE) when the current density reaches 10 mA cm(-2), which is much lower than that of 2.24 V versus RHE and 1.58 V versus RHE for TiO2-NTAs and Ni(OH)(2)/TiO2-NTAs, respectively.