Corrosion inhibition and stability enhancement of cobalt phosphide in aqueous solution by coating TiO2 layer

Transition metal phosphides (TMPs) exhibit excellent performance in many fields, and possess low over-potential and high activity for H2 generation in water splitting, but the TMPs application has been limited by its deactivation due to corrosion in aqueous media. Developing corrosion resistance strategies is beneficial for overcoming the instability of TMPs in aqueous media reactions. In this work, the reaction of cobalt phosphide (CoxP) with H2O has been studied in detail. The reaction of CoxP and water induced formation of hydrogen and Co2+ and PO43− ions. The corrosion rate and degree of CoxP in water are dependent on the crystal structure, morphology, and surface composition. The concentration of Co2+ and PO43− in CoxP water mixture was 27.6 and 33.0 mg L−1, respectively, and 64.9 μmol of H2 was formed after 3 h of reaction in the dark at 50 °C. As a result, Co(OH)2 was formed on the CoxP surface. Coating a TiO2 protective layer on the surface of CoxP could inhibit self-corrosion. Increasing the TiO2 loading and high-temperature annealing can enhance the anti-corrosion ability of CoxP effectively.