In situ interfacial optimization of CoOOH/W18O49/NF heterojunction for boosted water-splitting performance

The development of heterostructure electrocatalysts with abundant active sites as binderless electrodes is crucial for the improvment of the catalytic efficiency. Herein, the CoOOH/W18O49 heterojunction grown on nickel foam (abbreviated as Pre-CoOOH/W18O49/NF) was fabricated via a facile solvothermal method. It is found that in situ electrochemical reconstruction induces the amorphization of the non-stoichiometric tungsten oxide and effectively changes the interfacial interaction, which enables the electrons at the heterojunction interfaces to be redistributed. The Co2+/Ni2+ ions successfully optimize the valence configuration of tungsten (W) sites, leading to a high proportion of W4+ and Co3+/Ni3+ active sites. Simultaneously, the potential of the flat band becomes more negative than the reduction potential of hydrogen for the water splitting, so as to achieve enhanced intrinsic hydrogen evolution activity. As expected, the reconstruction contributes to more efficient electrocatalytic activity compared with that of the direct hydrogen/oxygen evolution in alkaline solution. The activated CoOOH/W18O49/NF electrode (abbreviated as Act-CoOOH/W18O49/NF) with the optimized amorphous-crystalline interface shows low overpotentials of 89 and 198 mV at 10 and 20 mA cm−2 for HER and OER, respectively. It only needs 1.55 V (10 mA cm−2) decomposition voltage for overall water splitting and retains a high stability at least 50 h.