Molecular and Material Engineering of Photocathodes Derivatized with Polyoxometalate-Supported {Mo₃S₄} HER Catalysts

Abstract

Molecular engineering of efficient HER catalysts is an attractive approach for controlling the spatial environment of specific building units selected for their intrinsic functionality required within the multistep HER process. As the {Mo 3 S 4 } core derived as various coordination complexes has been identified as one as the most promising MoS xbased HER electrocatalysts, we demonstrate that the covalent association between the {Mo 3 S 4 } core and the redox-active macrocyclic {P 8 W 48 } polyoxometalate (POM) produces a striking synergistic effect featured by high HER performance. Various experiments carried out in homogeneous conditions showed that this synergistic effect arises from the direct connection between the {Mo 3 S 4 } cluster and the toroidal {P 8 W 48 } units featured by a stoichiometry which can be tuned from two to four {Mo 4 S 4 } cores per {P 8 W 48 } unit. In addition, we report that this effect is preserved within heterogeneous photoelectrochemical devices where the {Mo 3 S 4 }-{P 8 W 48 } (thio-POM) assembly was used as co-catalyst (cocat) onto a microstructured p-type silicon. Using drop-casting procedure to immobilize cocat onto the silicon interface led to high initial HER performance under simulated sunlight achieving a photocurrent density of 10 mA.cm-2 at +0.13 V vs RHE. Furthermore, electrostatic incorporation of the thio-POM anion cocat into a poly(3,4-ethylenedioxythiophene) (PEDOT) film is demonstrated to be efficient and straightforward to durably retain the cocat at the interface of a micropyramidal silicon (SimPy) photocathode. The thio-POM/PEDOT-modified photocathode is able to produce H 2 under 1 Sun illumination at a rate of ca. 100 µmol cm-2 h-1 at 0 V vs RHE, highlighting the excellent performance of this photoelectrochemical system.

Time‐Resolved Spectroscopy and High‐Efficiency Light‐Driven Hydrogen Evolution of a {Mo3S4}‐Containing Polyoxometalate‐Based System

“…These absorptions correspond to Mo IV -centered d-d transitions and E®Mo LMCT (with E = S, O) [18,19] which are characteristic of {Mo3S4} covalently linked to polyoxotungstate units. [20] Moreover, a study of a similar compound with a-A-[SiW11O39] 8as lacunary Keggin subunits reported that both {Mo3S4} units are almost electronically uncoupled. [16] At working concentrations, the portion of light absorbed by the [Ir] at 450 nm is about 47% while in the presence of thio-POM, the attenuation of light in the most concentrated solution equals 98.8% for 2 cm optical path of the reactor.…”

“…[13] The resulting mixed Mo3S4-containing POM was shown to be a very efficient electrocatalyst for HER, functioning either in homogeneous or in heterogeneous conditions, as deposited co-catalyst on silicon photocathode. [14] Such a strategy was demonstrated as a general efficient approach to synthesize polymodular thio-POM species that exhibit various combinations, stoichiometries and structures. [15] In context, we report on the combination of the {Mo3S4} core with the monovacant anion a-A-[PW11O39] 7resulting of a similar structure scheme of that previously reported for the [{(SiW11O39)Mo3S4(H2O)3(µ-OH)}2] 10cluster.…”

“…[11,12] Using a similar approach, the cationic thiomolybdic core {Mo 3 S 4 } 4 + has been grafted on the crownshaped anion [H 7 P 8 W 48 O 184 ] 33À , [13] leading to an efficient HER electrocatalyst functioning either in homogeneous or in heterogeneous conditions, as deposited co-catalyst on silicon photocathode. [14] Such a strategy has been shown to be an effective general approach to synthesize polymodular species of ThioPOM with various combinations, stoichiometries and structures. [15] In context, we report on the combination of the {Mo 3 S 4 } core (Figure 1B) with the monovacant anion α-A-[PW 11 O 39 ] 7À (Figure 1C) which is expected to give the ThioPOM adduct with similar structure scheme of that previously reported by Müller et al (Figure 1D).…”

Advances of transition-metal-modified {P<sub>2</sub>W<sub>12</sub>}-based polyoxometalates

“…而在王恩波团队 [37] [35,37,64,66,67] . [82] ; (b) {Mo 9 S 12 }/PEDOT光阴极的光致析氢示意图; (c, d) 析氢实验前后, {Mo 9 S 12 }/PEDOT的扫描电子显微镜图 [83] (网络版彩图) [85] ; (b)在改变IO 3 − 浓度的Na 2 SO 4 -H 2 SO 4 溶液中的电流-时间响应曲线 [86] (网络 版彩图) Figure 11 (a) Schematic illustration on the preparation of {P 8 W 48 }-Cu@Ag composite film [85], and (b) current-time response curve with varying concentrations of IO [87] ; (b) 杂化材料{P 8 W 48 }-ZrO 2 的制备过 程示意图 [90] (网络版彩图)…”

“…a) The synthetic steps of P 8 W 48 @rGO composite[82]; (b) the schematic diagram for hydrogen evolution by {Mo 9 S 12 }/PEDOT photocathode; and the SEM pictures of {Mo 9 S 12 }/PEDOT (c) before and (d) after HER experiment[83] (color online).…”