Designing Efficient Solar‐Driven Hydrogen Evolution Photocathodes Using Semitransparent MoQ_xCl_y (Q = S, Se) Catalysts on Si Micropyramids

Abstract

Silicon micropyramids with n(+) pp(+) junctions are demonstrated to be efficient absorbers for integrated solar-driven hydrogen production systems enabling significant improvements in both photocurrent and onset potential. When conformally coated with MoSx Cly , a catalyst that has excellent catalytic activity and high optical transparency, the highest photocurrent density for Si-based photocathodes with earth-abundant catalysts is achieved.

Photo-assisted electrodeposition of MoSxfrom ionic liquids on organic-functionalized silicon photoelectrodes for H2generation

“…19 In two other cases, the research groups of Loo and Yang independently reported the integration of MoS 2 with silicon nanowire electrodes: an onset potential of +0.25 V (vs. RHE) for SiNW@MoS 2 in 1.0 M Na 2 SO 4 buffer (pH 5.0); +0.3 V (vs. RHE) for MoS 2 /TiO 2 /n + p-Si NW in 0.5 M H 2 SO 4 . 24 And although MoS 2 seems to t the requirement of a HER catalyst, all the deposition methods such as sputtering, sulfurization, and CVD present limitations in terms of economy, safety and performance. 22 The as-grown MoS 2 (2H-MoS 2 ) prepared by chemical vapor deposition was converted to metallic MoS 2 (1T-MoS 2 ) by chemical exfoliation with n-BuLi.…”

Nanostructured p-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes

“…Beside NiO [77,78,89] and Cu 2 O [90], other oxides [91][92][93] were studied as photocathodes for HER, e.g., the mixed oxides p-CaFe 2 O 4 [94] and p-LaFeO 3 with the latter system having presented an interesting value of hydrogen formation rate (11.5 mmol¨h´1) [95]. Metal sulfide photocathodes like CoS [96], CoS 2 [97,98] [99]), nitrides of semi-and non-metallic atoms (GaN [112] and C 3 N 4 [113]), borides of metals (Co 2 B [114]), arsenides of semi-metallic atoms or non-metals (GaPNAs [115], GaAs [116], AlGaAs [116]), tellurides of metals (CdTe QD [73]), and carbides of semi-metallic atoms (4H-SiC [117], 3C-SiC [118]). From the thermodynamic standpoint photoactivated HER can take place provided that p-type photoelectrodes have a small bandgap with respect to the energy separation of water splitting levels, and the lower edge of CB is above the energy level of H + reduction (Figures 16 and 17) [98,119].…”

“…Results of the photoelectrochemical performance achieved with PECs utilizing RGO-based photocathodes are reported in Table 4. Finally, we report now on the photoelectrocatalytic activity of p-Si based photocathodes for HER when silicon has different morphologies (nanowires, micropyramidal, nanomesh), various degree of doping (p-, n + and n + pp + ), and diverse types of photoelectrocatalyst (metallic, p-type semiconducting, metal alloy) [63,97,99,111,[125][126][127][128][129][130][131][132][133][134][135][136][137]. A scheme of the energy levels involved in the interface p-Si/electrolyte for HER is given in Figure 19 [126].…”

“…In fact, the systems possessing the most open morphologies, e.g., pyramids [99] or NWs [102], display the largest values of j ph,cat when Si is modified with Mo-based photocatalysts. In the framework of PECs with p-Si photocathodes for HER the most interesting finding is the comparable photoelectrochemical activity of these photoelectrodes when sensitized either with sulfide based semiconductors or with noble metals.…”

High performance nanostructured Silicon heterojunction for water splitting on large scales

“…Photo-electrochemical devices (PEC) for water splitting applications have stirred great interest, and different approach has been explored to improve the efficiency of these devices and to avoid optical losses at the interfaces with water. These include engineering materials and nanostructuring the device's surfaces [1]- [2]. Despite the promising initial results, there are still many drawbacks that needs to be overcome to reach large scale production with optimized performances [3].…”