Universal Strategy of Bimetal Heterostructures as Superior Bifunctional Catalysts for Electrochemical Water Splitting

Utilizing earth-abundant metals to design economical and efficient electrocatalysts for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) is critical for acquiring clean hydrogen energy by the electrochemical overall water-splitting system. In this work, we reported a facile and universal strategy toward developing a suite of bimetallic heterostructures, representing as highly efficient catalysts of the HER/OER process. By hybridizing transition-metal sulfides (CoS2, NiS2, FeS2, and CuS) with highly active MoS2 nanosheets, all heterostructural catalysts achieved largely improved bifunctional activity originating from the special interfacial interaction as well as synergetic catalytic effects. As a result, the optimal CoS2@MoS2/CC and NiS2@MoS2/CC heterostructures displayed the lowest overpotentials at 10 mA cm–2, which only required 31 and 225 mV for HER/OER, respectively. After assembling for water splitting, the electrolyzer exhibited a very small cell voltage of 1.58 V to reach 10 mA cm–2. This result is obviously better than a lot of reported non-precious metal catalysts. Our strategy experimentally confirms the feasibility of the heterostructure to enhance the bifunctional performance of advanced electrocatalysts for electrochemical water splitting.