Abstract
Ir‐implanted titanium near‐surface alloys were prepared by ion implantation, characterized (Ir concentration/depth profiles) by Rutherford backscattering (RBS), and subsequently anodically oxidized to form electrocatalytically active
electrodes. The electrochemical behavior of the metallic‐like 
electrodes in acidic chloride, sulfate, and perchlorate solutions was investigated, and the results compared with those previously obtained with similarly prepared 
electrodes. For both electrodes, 
, the Tafel slope for the 
evolution reaction is 40 mV, i.e., 
. The reaction order 
with respect to chloride ion concentration, 
, approaches limiting values of 1.0 and 2.0 at high and low chloride ion concentrations, respectively, i.e., 
, where 
for 
and 
for 
. A modified Volmer‐Heyrovsky mechanism, one in which the role of adsorbed chloride ions is taken into account, is shown to be consistent with the aforementioned diagnostic parameters. A correlation of the rate of 
evolution with the M‐implant profiles enabled the determination of the instantaneous in situ surface concentration of the catalytically active M(IV) component of the 
electrodes. This, in turn, enabled the evaluation of the specific catalytic activities (rate per catalyst surface site) of 
and 
, and their relative catalytic activity. 
is only 45% as effective a catalyst for 
evolution as 
, but it is far more stable, i.e., its corrosion rate is only ∼5% that of
.