An integrated cobalt disulfide (CoS₂) co-catalyst passivation layer on silicon microwires for photoelectrochemical hydrogen evolution

Abstract

Integrated cobalt disulfide (CoS2) co-catalyst passivation layer on Si microwires (MWs) were used as a photocathode for solar hydrogen evolution. Si MWs were prepared by photolithography and dry etching technique. The CoS2-Si photocathodes were subsequently prepared by chemical deposition and thermal sulfidation of the Co(OH)2 outer shell. The optimized onset potential and photocurrent of the CoS2-Si electrode were 0.248 V and −3.22 mA cm −2 (at 0 V), respectively. The best photocatalytic activity of the CoS2-Si electrode resulted from lower charge transfer resistances among the photoabsorber, co-catalyst, and redox couples in the electrolyte. X-ray absorption near edge structure was conducted to investigate the unoccupied electronic states of the CoS2 layer. We propose that more vacancies in the S-3p unoccupied states of the CoS2-Si electrode were present with a lower negative charge of S2 2to form weaker S-H bond strength, promoting water splitting efficiency. Moreover, the CoS2 co-catalyst that completely covered underlying Si MWs, was served as a passivation layer to prevent oxidation and reduce degradation during photoelectrochemical measurements. Therefore, the optimal CoS2-Si electrode maintained the photocurrent at about −3 mA cm −2 (at 0 V) for 9 h, and its hydrogen generation rate was approximately 0.833 μmol min −1 , respectively.

The Design of a New Cobalt Sulfide Nanoparticle Implanted Porous Organic Polymer Nanohybrid as a Smart and Durable Water‐Splitting Photoelectrocatalyst

“…[41] The high-resolution N1sX PS peak appearing at 398.9 eV could be assigned to the presence of the mono-functional symmetrical nitrogen group on POP surface, supplying additional evidence for the formation of aC o-N x bond which is beneficial in improving electrocatalytic activity (Figure 6f). [42][43][44][45] The onset overpotential of the photocurrent of CoS x @POP film is approximately 92 mV versus RHE.T he photocurrentd ensity of the pristine Co 3 O 4 and CoS x is not high with the value of ca.À1.5 andÀ2.5 mA cm À2 at 0Vversus RHE, whichi sq uite similar to each other in terms of over potential. Similarly,t he positive displacement in the binding energies in the N1Ss pectrum of CoS x @POP compared with the bare POP demonstrated the interaction between the N-rich POP and cobalt sulfide nanoparticles which builds a" bridge"f or the charge transfer between POP and Co 9 S 8 (Figure 6f).…”

Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

“…Pan et al constructed TiO 2 p-n homojunction to realize enhanced PEC H 2 evolution performance. Virtually, it is revealed that most of the excellent PEC water splitting cocatalysts are electrocatalysts, [18][19][20] such as transition metal dichalcogenides (TMDs), [21][22][23][24][25] phosphorous metal compounds, [26][27][28] metal oxides, [29][30][31][32] metal hydroxides, [29,33] etc. [16] Alternatively, engineering cocatalysts on the surface of photoelectrodes gradually came to sight recently, as the existence of cocatalysts can bring about the reduced overpotential, accelerated reaction kinetics, enriched active sites, and suppressed corrosion.…”

Hybrid Dot–Disk Au-CuInS2 Nanostructures as Active Photocathode for Efficient Evolution of Hydrogen from Water

“…The R ct1 signifies charge transfer resistance between PEDOT:PSS layer and the active material, whereas R ct2 refers to charge transfer resistance between the electrolyte and photoactive layer. 65 The resistive characteristics of the photocathodes are tabulated in Table S2. The solution resistance and R ct1 were found to be slightly different for different photocathodes.…”