Ti-assisted electrochemical reconstruction of CoCuCeMo xerogel-derived electrocatalysts for enhanced oxygen evolution

Abstract

The alkaline oxygen evolution reaction (OER) remains a slow anodic step in water electrolysis, so low-cost electrocatalysts that operate at reduced overpotential are still required. Here, CoCuCeMo multicomponent xerogel electrodes were prepared on nickel foam by a propylene oxide-assisted sol-gel route, which offers a mild and composition-tolerant platform for electrode construction. Ti was subsequently placed on the xerogel surface by DC magnetron sputtering with four nominal thicknesses (Ti-2.5, Ti-5, Ti-10 and Ti-20); Ti-free CoCuCeMo (Ti-0) and Ti sputtered on bare nickel foam (NF/Ti-10) were used for comparison. After electrochemical activation in 1 M KOH, each Ti-modified electrode showed higher activity than Ti-0. The optimized Ti-10 electrode required 214.2 mV to reach 10 mA cm-2, which is 35.3 mV lower than Ti-0 (249.5 mV). The weak performance of NF/Ti-10 shows that Ti deposition by itself is not the direct origin of the improvement. Meanwhile, the small change in Cdl among the Ti-modified samples suggests that the gain in activity is not simply caused by a larger accessible electrode/electrolyte interface. EDS analysis shows that, after activation, Ti in Ti-10 decreases from 1.22 to 0.25 at%, while Mo becomes undetectable by EDS. TEM/SAED and XPS indicate that the activated surface is a low-crystallinity Co-based (oxy)hydroxide layer containing residual Ti4+-related species. These results support a deposition-dissolution-residue picture for Ti-regulated electrochemical reconstruction and show that sputtering-assisted surface modification can tune reconstructable multicomponent non-noble-metal OER catalysts.