Supercritical　water　gasification　is　an　innovative　handling　method　of　black　liquor,　which　can　also　produce　hydrogen-rich　gases.　In　this　study,　the　catalytic　activity　of　14　common　metal　oxides　on　SCWG　of　black　liquor　were　investigated　and　the　catalytic　mechanism　was　studied　through　X-ray　photoelectron　spectroscopy　(XPS)　analysis.　All　the　tested　oxides　improved　the　gasification　efficiency　and　V2O5,　WO3　and　Co2O3　showed　the　highest　performance.　The　H2　yields　of　21.67　and　21.03　mol/kg　were　achieved　with　the　presence　of　Co2O3　and　ZnO　respectively.　The　gasification　efficiency　increased　with　the　increasing　V2O5　amount,　but　the　H2　fraction　increased　firstly　and　then　decreased.　The　highest　H2　fraction　of　44.59%　was　obtained　with　V2O5　loading　amount　of　45　wt%.　The　increase　of　reaction　time　improved　the　CE,　but　the　further　prolongation　had　little　influence.　The　XPS　analysis　of　CuO　and　Fe2O3　showed　some　of　them　were　reduced　to　metal　(Cu)　or　lower-valence　oxides　(Cu2O,　FeO).　The　metal　oxides　probably　promoted　black　liquor　decomposition　by　introducing　reactive　oxygen,　and　the　generated　metal　also　catalyzed　the　gasification.　Accordingly,　an　oxidation　reactor　could　be　introduced　to　recycle　the　metal　oxides,　which　may　help　to　realize　the　complete　gasification　of　black　liquor　or　other　refractory　wastes　at　milder　temperatures.　©　2020　Elsevier　Ltd