In electrocatalytic water splitting, low-cost dual-functional catalysts can not only reduce costs but also avoid cross-contamination of cathode and anode. However, the orderly aggregation of active sites for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) into a specific catalyst is very challenging. In this study, a Co/Fe₃O₄ Janus heterojunction supported on carbon fiber paper (J-CoFe-CFP) is designed and successfully synthesized. Generally, Co-Fe oxides have preferable OER activity but weak HER activity. However, in J-CoFe-CFP, due to the intense and special electronic interaction of different substances (Co and Fe₃O₄) in the Janus heterogeneous interface, a huge number of tidy high-quality HER and OER active sites are uniformly distributed on the interface simultaneously, which endows the catalyst with both excellent HER and OER performance. In HER, the overpotential @10 mA·cm⁻² (η_HER) is only 53.9 mV, and the Tafel slope is 43.7 mV·dec⁻¹. In OER, the η is 272 mV, and the Tafel slope is 50.2 mV·dec⁻¹, much lower than those of RuO₂/CFP. In the J-CoFe-CFP‖J-CoFe-CFP two-electrode system, the required voltage is only 1.26 V at the beginning and 1.56 V@10 mA·cm⁻², much lower than those of RuO₂/CFP‖20% Pt/C/CFP. This work provides a Janus heterojunction pathway for bifunctional water electrolysis catalysts.

在电催化水分解中，低成本的双功能催化剂不仅可以降低成本，还可以避免阴极和阳极的交叉污染。然而，将析氢反应（HER）和析氧反应（OER）的活性位点有序聚集成特定的催化剂非常具有挑战性。在本研究中，设计并成功合成了碳纤维纸负载的 Co/Fe ₃ O _{4 Janus 异质结 (J-CoFe-CFP)。}通常，Co-Fe 氧化物具有较好的 OER 活性，但 HER 活性较弱。然而，在J-CoFe-CFP中，由于不同物质（Co和Fe ₃ O ₄)在Janus多相界面中，大量整齐、优质的HER和OER活性位点同时均匀分布在界面上，赋予了催化剂兼具优异的HER和OER性能。在HER中，过电位@10 mA·cm ^-2 ( η _HER )仅为53.9 mV，Tafel斜率为43.7 mV·dec ^-1。在OER中，η为272 mV，Tafel斜率为50.2 mV·dec ^-1，远低于RuO ₂ /CFP。在J-CoFe-CFP‖J-CoFe-CFP双电极体系中，开始时所需电压仅为1.26 V，10 mA·cm ⁻²时为1.56 V ，远低于RuO ₂/CFP‖20% Pt/C/CFP。这项工作为双功能水电解催化剂提供了 Janus 异质结途径。