The reaction is performed in a batch process, which starts with the activation of nickel foam by acidic washing (Scheme S4). This process removes the layer of nickel oxide that was present on the surface, which in turn enhances the catalytic performance. In theory, the catalyst wash produces a discharge solution containing nickel sulfate (NiSO4) dissolved in water, which is disposed of in compliance with lab waste management rules (no measurement has detected such a small flow of NiSO4 in wastewater). As the presence of nickel oxide is significantly reduced during operation, this substance was not considered for the risk assessment.