Activation and degredation of Co-based nitrate reduction electrocatalyst under relevant industrial conditions probed with XRD and XAS

The electrochemical reduction of nitrate into ammonia (NO3RR) is a promising approach to valorizing nitrogen waste from industrial point sources. Efficient catalysts based on metal-oxides/hydroxides, e.g. CoxOxHz, often undergo severe structural and compositional alterations during NO3RR which can even become superimposed by parasitic hydrogen evolution reaction (HER). Here, we apply a tandem X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) technique under operando conditions to probe for the first-time catalyst activation and possible degradation phenomena under realistic industrial conditions in flow-cell configuration using nitrate concentrations beyond 1 M and electrolytes with a pH 4.5. We will demonstrated to which extent the local increase of the surface pH at ampere level NO3RR rates may kinetically stabilize cobalt oxides/hydroxides as active catalyst species even at mildly acid pH in the ”bulk” electrolyte solution.