Ammonia　decomposition　is　a　crucial　pathway　for　hydrogen　production,　holding　significant　promise　for　sustainable　and　efficient　energy　generation.　Initial　investigations　in　this　study　reveal　that　internal　diffusion　limitations,　influenced　by　the　size　of　industrial　catalyst　particles,　severely　impact　catalytic　performance　in　an　External　Wall-Heated　Reactor　(EWHR),　with　smaller　powders　causing　excessive　pressure　drop.　The　introduction　of　washcoated　SiSiC　foam　effectively　mitigates　diffusion　limitations,　thereby　enhancing　the　ammonia　decomposition　performance.　In　non-reactive　conditions,　the　Internal　Joule-Heated　Reactor　(IJHR)　demonstrates　remarkable　thermal　response　and　energy　efficiency　due　to　its　in-situ　Joule　heating　compared　to　the　EWHR.　For　ammonia　decomposition　process,　the　IJHR　also　exhibits　superior　catalytic　performance　and　lower　energy　consumption,　achieving　peak　energy　efficiency　at　600　degrees　C.　The　integration　of　IJHR　with　washcoated　SiSiC　foam　represents　an　innovative　breakthrough　in　hydrogen　production　via　ammonia　decomposition,　aligning　with　the　revolutionary　design　concept　of　IJHR　to　enhance　efficiency　and　energy　savings　for　industrial-scale　applications.