Pt-based bimetallic catalysts for SO2-depolarized electrolysis reaction in the hybrid sulfur process

SO2-depolarized electrolysis (SDE) is pivotal in the hybrid sulfur process, which is a promising approach for mass hydrogen production without CO2 emission. The anode overpotential of SDE is the key component of electrolysis potential. This factor can be reduced by improving anode reaction kinetics. Such improvement is commonly achieved by employing Pt/AC as anode electrode and catalyst, thus also improving economic and electrocatalytic performances. In this work, anode catalysts for SO2 oxidation reaction are experimentally studied. Platinum-based bimetallic catalysts, including Pt–Pd/C, Pt–Rh/C, Pt–Ru/C, Pt–Ir/C, and Pt–Cr/C, are prepared and characterized. Their electrochemical characteristics for SDE in a once-through mode are investigated in SO2-saturated 30 wt% sulfuric acid at room temperature by various approaches such as cyclic voltammetry, linear sweep voltammetry, and polarization curves. Results show that 60 wt% Pt–Cr/C exhibits the highest electrocatalytic activity for SDE. Further studies on the metal proportion in Pt–Cr/C show that at a Pt:Cr atomic ratio of 1:2, this bimetallic catalyst demonstrates equal or even better electrolysis performance than 60 wt% Pt/C at a significantly lower economic cost.