In-Situ Formation of CoP/Co3O4 Heterojunction for Efficient Overall Water Splitting.

Electrochemical water splitting is an environmentally friendly and effective energy storage method. However, it is still a huge challenge for preparing no-noble metal based-electrocatalysts which possess high activity and long-term durability to realize efficient water splitting. Here, we put forward a novel method of low-temperature phosphating to prepare CoP/Co3O4 heterojunction nanowires catalyst on titanium mesh (TM) substrate for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting. CoP/Co3O4@TM heterojunction showed an excellent catalytic performance and long-term durability in 1.0 M KOH electrolyte. The overpotential of CoP/Co3O4@TM heterojunction was only 257 mV at 20 mA cm-2 during the OER process, and it could work stably more than 40 h at 1.52 V versus reversible hydrogen electrode (vs. RHE). During the HER process, the overpotential of CoP/Co3O4@TM heterojunction was only 107 mV at -10 mA cm-2.  More importantly, when CoP/Co3O4@TM heterojunction were used as anodic and cathodic electrocatalysts, respectively, they displayed 10 mA cm-2 at 1.59 V. The Faradaic efficiencies of OER and HER were 98.4% and 99.4%, respectively. It was more excellent than the Ru/Ir-based noble metal electrocatalysts and other non-noble metal electrocatalysts which have been reported for overall water splitting.