Inverted Pyramid Textured p-Silicon Covered with Co₂P as an Efficient and Stable Solar Hydrogen Evolution Photocathode

Abstract

Silicon (Si) has been investigated as a promising photoelectrode material for use in photoelectrochemical water splitting. However, development of Si photocathodes that can operate at a high photocurrent density for solar-driven hydrogen production with long-term stability remains challenging. Herein, we report the fabrication of inverted pyramid textured p-Si photocathodes covered conformally and continuously with a thicknessgradient cobalt phosphide (Co 2 P) layer, which not only effectively isolates p-Si from aqueous electrolyte to avoid corrosion but also efficiently catalyzes the solar-driven hydrogen evolution reaction (HER). Thanks to the unique inverted pyramid structure, the dropcast Co 2 P can distribute all over the p-Si photocathode and form a macroscopically continuous but locally nonuniform layer on the sidewalls of each inverted pyramid. The local nonuniform distribution enables light absorption to be partially separated from catalytic activity. Consequently, the as-fabricated Co 2 P-coated p-Si photocathode exhibits a high photocurrent density of 35.2 mA cm −2 at 0 V versus the reversible hydrogen electrode under AM 1.5G illumination and can photoelectrochemically catalyze the HER above 30 mA cm −2 at least 150 h without notable degradation.

Strategies for Semiconductor/Electrocatalyst Coupling toward Solar‐Driven Water Splitting

“…The as‐deposited Co 2 P layer not only served as a highly active HER catalyst but effectively passivated Si against corrosion, in such a way both the PEC HER activity and stability were remarkably improved (Figure 13h). Furthermore, using a similar method the same group recently demonstrated that a Co 2 P layer with a thickness gradient can be conformally and continuously deposited on inverted pyramid‐textured Si photocathode . The thickness‐gradient Co 2 P layer enabled partial spatial decoupling of light‐absorption and catalytic activity, and in this way the photocathode could deliver a photocurrent density as high as 35.2 mA cm −2 at 0 V RHE and show excellent stability of 150 h at a high photocurrent density of above 30 mA cm −2 under PEC operational conditions.…”

One-step synthesis of single-site vanadium substitution in 1T-WS2 monolayers for enhanced hydrogen evolution catalysis

“…Recently, various strategies have been developed to realize the highly efficient catalysts for hydrogen evolution reaction (HER), including semiconductor-based photocatalytic HER (polymer g-C 3 N 4 3 , Ag/semiconductor 4 , etc. ), photoelectrochemically catalytic HER 5 , and metal-based electrocatalytic HER (metal sulfides 1 , 6 , 7 , metal carbides 8 , 9 , etc.). Commercially, noble metals from the Pt group are utilized to reduce the overpotential of HER and boost the kinetics with unrivaled activities, however, they usually suffer from scarcity, high-cost, and long-term instability.…”

Extraterrestrial artificial photosynthetic materials for in-situ resource utilization

“…Numerous p-type semiconductors have been exploited and investigated for photocathodes, including p-type silicon [ 67 ], oxides [ 68 – 73 ], sulfides [ 74 ], phosphides [ 67 ] and selenides [ 75 ]. Tellurides [ 76 ] have been investigated for CO 2 reduction or H 2 O reduction.…”