A copper catalyst is active towards water reduction with distinctive pH-dependent mechanisms. The CuIII–H− intermediate is bypassed by PCET processes.

The cobalt complex, [Co­(CR)­Br2]+, where CR is the redox-active macrocycle 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]-heptadeca-1(17),2,11,13,15-pentaene, has been investigated for the electrocatalytic reduction of aqueous NO2 – and NO3 –. At neutral pH, the bromide ligands are hydrolyzed, providing [Co­(CR)­(OH2)­(OH)]2+ as the major species in aqueous solution. In the presence of nitrite, [Co­(CR)­(NO2)2]+ is formed as the major species in solution and is a precursor to the electrocatalytic reduction of NO2 –, which is selectively converted to ammonium with high Faradaic efficiency. There is evidence for both homogeneous and heterogeneous electrocatalysis. Although similar NO3 – binding is not observed, electrocatalytic reduction to ammonium also occurs, albeit with a lower Faradaic efficiency. In this case, NO2 – is generated as an intermediate product of NO3 – reduction.

Electrochemical arrays promise utility for accelerated hypothesis testing and breakthrough discoveries. Herein, we report a new high-throughput electrochemistry platform, colloquially called "Legion," for applications in electroanalysis and electrosynthesis. Legion consists of 96 electrochemical cells dimensioned to match common 96-well plates that are independently controlled with a fieldprogrammable gate array. We demonstrate the utility of Legion by measuring model electrochemical probes, pH-dependent electron transfers, and electrocatalytic dehalogenation reactions. We consider advantages and disadvantages of this new instrumentation, with the hope of expanding the electrochemical toolbox.