From 3D to 2D Co and Ni Oxyhydroxide Catalysts: Elucidation of the Active Site and Influence of Doping on the Oxygen Evolution Activity

Layered oxyhydroxides (ox-hys) of Ni and Co are among the most active catalysts for oxygen evolution in alkaline media. Their activities can be further tuned by delamination into single-layer oxide sheets or by means of doping. The active site for the reaction and how doping and delamination promote the intrinsic activity, however, remain elusive. To shed light on these open questions, we have undertaken a systematic analysis of the stability, catalytic activity, and electronic conductivity of Ni and Co ox-hys ranging from bulk (3D) to single-layer (2D) catalysts. In both cases, we investigate the role of terrace and edge sites and use stability, catalytic activity, and electronic conductivity as evaluation criteria to pinpoint the best catalysts. We arrive at several important conclusions: the ox-hy surface is fully oxidized under oxygen evolution conditions, bulk terraces are ostensibly the most active sites, and Ni ox-hy sheets are more electronically conductive in comparison to their Co equivalents. F...