Development　of　electrocatalytically　active,　durable　hydrogen　electrode　materials　is　vital　for　solid　oxide　cells　(SOCs).　La0.75Sr0.25Cr0.5Mn0.5O3　(LSCM)　hydrogen　electrode　shows　great　potential　for　durability　in　a　harsh　operational　environment,　although　its　practical　application　is　critically　limited　by　the　low　intrinsic　electrocatalytic　activity.　Herein,　a　heterogeneous　LSCM-Gd0.1Ce0.9O1.95　(GDC)　nanocomposite　hydrogen　electrode　is　synthesized　by　coupling　a　self-assembly　synthesis　method　with　a　sintering-free　direct　assembly　technique.　The　self-assembly　method　gives　rise　to　the　formation　of　a　nanocomposite　with　a　robust　LSCM-GDC　heterointerface　and　increased　surface　oxygen　vacancies.　The　direct　assembly　method　enables　preservation　of　the　original　nanostructure　and　heterointerface　in　the　hydrogen　electrode,　and　the　subsequent　electrochemical　polarization　induces　in　situ　construction　of　a　coherent　electrode|electrolyte　interface.　A　corresponding　electrolyte-supported　single　cell　achieves　a　peak　power　density　of　1.04　W　cm-2　and　an　electrolysis　current　density　of　1.51　A　cm-2@1.5　V　in　pure　CO2　at　850　degrees　C.　The　cell　shows　no　noticeable　degradation　during　200　h　galvanostatic　test　in　fuel-cell　and　electrolysis　modes.　This　work　provides　an　innovative　approach　for　the　development　of　LSCM-GDC　nanocomposite　electrodes　for　efficient　and　durable　SOCs.