Heterostructure of Si and CoSe₂: A Promising Photocathode Based on a Non‐noble Metal Catalyst for Photoelectrochemical Hydrogen Evolution

Abstract

Development of a solar water splitting device requires design of a low-cost, efficient, and non-noble metal compound as alternative to noble metals. For the first time, we showed that CoSe2 can function as co-catalyst in phototoelectrochemical hydrogen production. We designed a heterostructure of p-Si and marcasite-type CoSe2 for solar-driven hydrogen production. CoSe2 successively coupled with p-Si can act as a superior photocathode in the solar-driven water splitting reaction. Photocurrents up to 9 mA cm(-2) were achieved at 0 V vs. reversible hydrogen electrode. Electrochemical impedance spectroscopy showed that the high photocurrents can be attributed to low charge transfer resistance between the Si and CoSe2 interfaces and that between the CoSe2 and electrolyte interfaces. Our results suggest that this CoSe2 is a promising alternative co-catalyst for hydrogen evolution.

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).…”

“…All the photocurrents exhibited ar eductive photocurrent, which is attributed to the PEC water reduction. [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. However, after grafting on the surface of the POP,t he biphasic composite system showed enhanced current density with lowering of the over potential to 0.18 and 0.25 Vf or Co 3 O 4 @POP and CoS x @POP respectively.…”

“…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). [22,45,46] The reversibility of the photoactivity of the as-prepared photocathodes was investigated using amperometricm easurements at relativelyh igher appliedv oltage of À0.7 Vv ersus RHE. For the sake of completeness of the experiment, Co 3 O 4 @POP, CoS x and spinel Co 3 O 4 species were takena sc ontrols.…”

“…[46] It is worth mentioning here that the photo- current recorded with CoS x @POP photocathode is found to be comparable to many recently reported photocathodes comprised of polymer and/or cobaltc halcogenides. [22,45,46] The reversibility of the photoactivity of the as-prepared photocathodes was investigated using amperometricm easurements at relativelyh igher appliedv oltage of À0.7 Vv ersus RHE. Figure 7b shows the transient photocurrent response of the different photocathode materials.…”

“…This is clearly attributed the synergistic effect of POP towards the separation of electron-hole pair and lowering the resistance for vectorial transfer of electron into electrolyte solution, which resembles as imilars tudy,e xplored in the previous work. [45] For the assessment of the chemicals tability and catalytic durability of our newly designed CoS x @POP PEC catalyst, we have carried out the powderX RD of the respective materials after being stored in open air for about 2weeks and we have observed no detectable phasec hange in that PXRD pattern ( Figure S3, Supporting Information). This crucial observation revealed that chemical stabilityo fo ur catalyst is significantly improved towards air and moisturea fter successful interaction with the N-doped porouso rganic polymer which was not likely to have happened for the CoS 2 /CNT catalysta sr eported by Wang et al [23] In order to investigate chemical and mechanical stabilityo ft he used CoS x @POP catalyst after PEC test, we have characterised the used catalystb ye mploying TEM, 13 CC Ps olid state MAS NMR spectroscopya nd XPS analysis.…”