N-doped TiO 2 nanotube arrays with uniformly embedded Co x P nanoparticles for high-efficiency hydrogen evolution reaction.

Efficient and stable non-precious metal based electrocatalysts are crucial to the hydrogen evolution reaction (HER) in renewable energy conversion. Herein, Co x P nanoparticles (NPs) are uniformly embedded in N-doped TiO 2 nanotube arrays (Co x P/N-TiO 2 NTAs) by low-temperature phosphorization of the precursor of metallic cobalt NPs embedded in N-doped TiO 2 NTAs (Co/N-TiO 2 NTAs) which were fabricated by phase separation of CoTiO 3 NTAs in ammonia. Owing to the abundant exposed surface active sites of Co x P NPs, tight contact between the Co x P NPs and TiO 2 NTAs, fast electron transfer in N-doped TiO 2 , and channels for effective diffusion of ions and H 2 bubbles in the tubular structure, the Co x P/N-TiO 2 NTAs have excellent electrocatalytic activity in HER exemplified by a low overpotential of 180 mV at 10 mA cm -2 and small Tafel slope of 51 mV dec -1 in 0.5 M H 2 SO 4 . The catalyst also shows long-term cycling stability and is a promising non-precious metal catalyst for HER.