Suppressing hydrogen evolution in copper oxides for CO2 electroreduction by tuning metal oxide supports

Abstract In this work, a range of supported copper oxides were synthesised via a simple deposition precipitation method, and their catalytic performance for the hydrogen evolution reaction (HER) was analysed, evaluating the influence of the support on catalytic activity. Electrochemical measurements showed that Cu 2 O containing catalysts had superior HER activity compared to CuO containing catalysts, achieving lower HER overpotentials and Tafel slope values. The SnO 2 support showed the largest HER suppression, desirable for use within the CO 2 reduction reaction (CO 2 RR), reducing the activity of the competing reaction, achieving a large HER overpotential value of 0.73 V vs. RHE, along with a small HER exchange current density of 5.93 µA/cm 2 , for Cu 2 O/SnO 2 , shown to be through possessing large HER charge-transfer resistance and small electrochemically active surface areas. The ZnO support was also shown to be adequate at supressing the HER activity, whilst also achieving the highest electrochemically active surface area for the reduction reactions to proceed on, out of all supported catalysts assessed in this work.