Evaluation of sputtered nickel oxide, cobalt oxide and nickel–cobalt oxide on n-type silicon photoanodes for solar-driven O₂(g) evolution from water

Abstract

Thin films of nickel oxide (NiOx), cobalt oxide (CoOx) and nickel–cobalt oxide (NiCoOx) produced integrated, protected Si (111) photoanodes integrated, protected Si photoanodes that did not require deposition of a separate heterogeneous electrocatalyst for water oxidation.

Strategies To Construct n-Type Si-Based Heterojunctions for Photoelectrochemical Water Oxidation

“…The deposition of a multifunctional layer that served as both protective layer and electrocatalytic layer on the semiconducting absorber without sacrificing device efficiency should be desired, because of the simplified synthesis process. Various transparent conductive oxides (TCOs) with catalytic activity have been employed as a protective layer on n -Si directly to form highly efficient and stable photoanodes, including NiO x , − ,,− CoO x , ,,− NiCoO x , , IrO x , NiRuO x , NiMoO x , IrO x -RuO x , , MnO x , ,, FeO x , etc.…”

“…Similarly, introducing other ternary p -TCOs (NiMoO 4 , NiRuO x ) on n -Si also showed no obvious enhancement in PEC performance relative to that of NiO x and CoO x coatings. , Thus, more work should be conducted to improve the interface between n -Si and ternary p -type transparent conductive oxides and the crystalline quality of oxides to form a high-quality heterojunction with high photovoltage. Yang et al systematically evaluated and compared the PEC performance of NiO x -, CoO x -, and NiCoO x -coated n -Si photoanodes . The deposition of sputtered p -TCO (75 nm) on n -Si showed similar onset potential but different saturated photocurrent ( j NiOx > j NiCoOx > j CoOx ) for PEC oxidation in 1 M KOH.…”

Ultrathin Cobalt Oxide Interlayer Facilitated Hole Storage for Sustained Water Oxidation over Composited Tantalum Nitride Photoanodes

“…Interestingly, iron, nickel, and cobalt mixed oxide/hydroxides in terms of electrochemical water oxidation reaction have been reported to exhibit high electrocatalytic activity and stability for oxygen evolution due to the strong electronic interactions between two elements, the charge-transfer activation effect, and heterojunction formation. − It thus provides guidance for designing transition-metal-based interfacial modification layers to help boost the photoelectrochemical (PEC) water splitting owing to its great hole extraction/transport ability and high valence state active species generation. − Thereinto, CoO x has been widely applied as an earth-abundant and low-cost oxygen-evolving cocatalyst for achieving efficient PEC water splitting. ,, Most importantly, Co–Ni mixed hydroxides exhibit preferable electrochemical water oxidation activity compared to Ni (hydro)­oxide, primarily due to the increase of Co active sites as well as synergy effects. , Typically, the NiO x /CoO x layer has been applied in interfacial engineering for yielding improved performance and stable photoelectrodes, primarily due to the synergistic effects between NiO x and CoO x . , However, apart from the role of accumulating charge-transfer kinetics, the underlying mechanism of CoO x for charge-transfer modulation remains in its infancy. To address the deficiency, Dai et al established a qualitative relation between interfacial charge recombination and hole-storage capacity of the electrocatalyst CoO x .…”

Defect-Tolerant TiO2-Coated and Discretized Photoanodes for >600 h of Stable Photoelectrochemical Water Oxidation

“…The (111)Si was reported to be stable for operating in an alkaline condition due the local self-passivation. 22 The stability of the GaAs nanowire top/Si bottom tandem structure was also compared directly to the behavior of GaAs nanowires grown on corrosion-susceptible substrates, e.g., degenerately doped GaAs (111)B. The comparison should test the defecttolerant strategy and demonstrate self-limiting corrosion mitigation.…”