▎ 摘　　要

NOVELTY - A tin(IV) oxide powder comprises 90 %mass or more hollow spheres comprising tin(IV) oxide particles, and having a size (diameter) of 175-225 nm, preferably 190-210 nm. USE - Tin(IV) oxide powder is used in ink for forming catalyst for manufacturing electrode used in system for converting carbon dioxide into formate or formic acid (all claimed) which is used as emerging fuel for fuel cell, liquid hydrogen carrier with high volumetric capacity and biomass upgrading applications. ADVANTAGE - The three-dimensional hollow nanosphere electrocatalyst formed using the tin(IV) oxide powder with heterogeneous size distribution enables conversion of carbon dioxide into formate with high current density and Faradaic efficiency. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: manufacture of tin(IV) oxide catalyst, which involves providing a suspension of polymer particles, combining a tin salt with the suspension, removing the liquid from the suspension by evaporation to form tin-coated polymer particles, drying the tin-coated polymer particles, and calcining the dried particles to burn out the polymer particles to obtain hollow tin(IV) oxide spheres; a catalyst ink, which comprises the tin(IV) oxide particles dispersed in a liquid phase along with conductive particles and binder particles; an electrode, which comprises a conductive substrate coated with the tin(IV) oxide powder; manufacture of the electrode; a system, which comprises the electrode arranged in a solution that is saturated with carbon dioxide; and conversion of carbon dioxide into formate or formic acid, which involves contacting a tin(IV) oxide-coated electrode with carbon dioxide and water, and passing an electrical current through the electrode, where the carbon dioxide and water react over the tin(IV) oxide catalyst to form formate. The catalyst has a Faradaic efficiency to formate of 50% or more, preferably 60-85% after operating for at least 24 hours without replacing or regenerating the electrode, measured at a potential in the range of 0.7-1.4 V vs. reversible hydrogen electrode, preferably 0.9-1.3 V vs. reversible hydrogen electrode.