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

Abstract 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, Ni 2 P clusters sensitized TiO 2 nanotube arrays photoanode (Ni 2 P/TiO 2 ‐NTAs) for PEC‐UOR with high efficiency are developed. The 1D TiO 2 ‐NTAs structure accelerates urea molecules diffusion and promotes CO 2 gas release at the electrode interface. Meanwhile, Ni 2 P is also beneficial to urea molecule absorption and CO 2 desorption and enable to lower the energy barrier for amine (NH) dehydrogenation. Furthermore, the robust interfacial charge transfer pathway between Ni 2 P and TiO 2 interface promotes the separation of photogenerated electrons and holes and the transfer of photogenerated electrons from Ni 2 P to TiO 2 . 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 TiO 2 ‐NTAs and Ni(OH) 2 /TiO 2 ‐NTAs, respectively.