Activating Inert ZnO by Surface Cobalt Doping for Efficient Water Oxidation in Neutral Media

Abstract

Precisely modulating the electronic structure of catalytic sites represents a promising strategy to design highly efficient electrocatalysts toward oxygen evolution reaction (OER). Here, the non-noble metal Co is successfully doped into the surface layer of ZnO and the doping concentration can be controllably adjusted by a partial cation exchange method. Our experimental and theoretical results demonstrate that the surface-doped Co can not only activate the inherently inert Zn sites by modifying their electronic structure and thereby promoting the OH* adsorption but also serve as active sites themselves for the adsorption of O* and OOH*, ultimately realizing the bimetallic synergetic effect in Co/ZnO for OER catalysis. Besides, the surface Co doping also benefits the obvious enhancement of electrical conductivity of the ZnO host. Therefore, relative to the inactive ZnO, the as-prepared Co/ZnO exhibits a much smaller overpotential and Tafel slope toward OER. This strategy provides a rational design of low-cost and efficient OER electrocatalysts.

Tuning the intrinsic catalytic activities of oxygen-evolution catalysts by doping: a comprehensive review

“…Mn and F dual-doped Ni(OH)2 91 233 mV @ 20 mA cm -2 56.9 10 h @ 20 mA cm -2 1 M KOH Ni-doped Co(OH)2 92 300 mV @ 10 mA cm -2 47 36 h @ 1.55 V vs RHE 1 M KOH Ni-doped FeOOH 93 239 mV @ 10 mA cm -2 90.4 -1 M KOH Ni0.83Fe0.17(OH)2 94 245 mV @ 10 mA cm -2 61 10 h @ 10 mA cm -2 1 M KOH Se-doped FeOOH 95 348 mV @ 500 mA cm -2 54 100 h @ 100 mA cm -2 1 M KOH W-doped Ni(OH)2 96 237 mV @ 10 mA cm -2 33 -1 M KOH Other oxides Ce-doped NiO-Au 97 244 mV @ 100 mA cm -2 >24 h @ 50 mA cm -2 1 M KOH Co-doped CuO 98 299 mV @ 50 mA cm -2 134 15 h @ 300 mV 1 M KOH Co-MnO2/OV 99 279 mV @ 20 mA cm -2 75 12 h @ 10 mA cm -2 1 M KOH Co-doped ZnO 100 450 mV @ 10 mA cm - portrays augmented OER activity among this series. 78 From the mechanism, superior OER activity is found to be linked with the reduction potential of Mn (IV) cation; and greater reduction potential facilitates improved kinetics by directly driving surface oxidation.…”

“…Interestingly, a small amount of cobalt doping (3.47%) could activate the OER activity of ZnO. Theoretical studies suggest that Co activates inherently inactivate adjacent Zn sites by increasing conductivity, acting as OER active sites for adsorption OER intermediates 100. Co doping also activates the OER activity in CuO.…”

Optimization and Modulation Strategies of Zinc Oxide-based Photoanodes for Highly Efficient Photoelectrochemical Water Splitting

“…72 Meng et al have doped Co into the surface of ZnO by a partial cation exchange process, demonstrating that the electrical conductivity of ZnO was enhanced and the active sites for OER were increased. 73 3.4. Other Semiconductor Coupling.…”

Amorphous Doping Promotes Utilization of Fe‐Doped Amorphous Zr(HPO4)2 for Superb Water Oxidation Electrocatalysis

“…[6][7][8] Besides, the doped hetero-atoms could serve as active sites, inducing a giant advance in the catalytic activity enhancement. [9][10][11] Up to now, there are many researchers reported doping transition metals such as Fe, [12,13] Co, [14,15] Ni, [16,17] is reported to serve as OER catalysts, shows an overpotential of 410 mV at a current density of 3 mA cm −2 , [36] which is still far from a satisfactory electrocatalyst. Therefore, it is significant to design and utilize novel as well as earth-abundant α-ZrP with high electrochemical activity for the OER rationally.…”