Although extracting carbon atoms from carbides, as the reverse route to carbide derived carbon (CDC), may have more potentials for constructing advanced nanostructures, it has not been realized yet. As a proof of concept, in this work we realize the extraction of carbon atoms from carbide lattices by rationally controlling the reaction between carbides and Cl2. Thus, a homologous metallic W layer adhered on a WC (W/WC) heterostructure is created. Based on experimental results, such a W/WC heterostructure can be used as an efficient catalyst for the photoelectrocatalytic hydrogen evolution reaction (HER), where the photocurrent density at 0 V can reach up to 16 mA cm-2. Our theoretical calculations disclose that the Mott-Schottky effect accelerates electron flow across the interfaces and significantly decreases the work function of the W facet, which leads to excellent photoelectrocatalytic HER activity on the W facets. The presented results have broad implications since they demonstrate the generic capability to build homologous M/TMC heterostructures.