Interfacial sp C–O–Mo Hybridization Originated High-Current Density Hydrogen Evolution

Abstract

High-current density (≥1 A cm–2) is a critical factor for large-scale industrial application of water-splitting electrocatalysts, especially seawater-splitting. However, it still remains a great challenge to reach high-current density due to the lack of active and stable intrinsic catalytic active sites in catalysts. Herein, we report an original three-dimensional self-supporting graphdiyne/molybdenum oxide (GDY/MoO3) material for efficient hydrogen evolution reaction via a rational design of “sp C–O–Mo hybridization” on the interface. The “sp C–O–Mo hybridization” creates new intrinsic catalytic active sites (nonoxygen vacancy sites) and increases the amount of active sites (eight times higher than pure MoO3). The “sp C–O–Mo hybridization” facilitates charge transfer and boosts the dissociation process of H2O molecules, leading to outstanding HER activity with high-current density (>1.2 A cm–2) in alkaline electrolyte and a decent activity and stability in natural seawater. Our results show that high-current density electrocatalysts can be achieved by interfacial chemical bond engineering, three-dimensional structure design, and hydrophilicity optimization.

Recent Advances in Design of Electrocatalysts for High‐Current‐Density Water Splitting

“…The state-of-the-art electrocatalysts developed for HCD water splitting include HER electrocatalysts such as Pt-based nanoparticles, [20,21] transitional metal phosphides, [22,23] sulphides, [24,25] and oxides, [26] as well as OER electrocatalysts such as Ir-and Ru-based nanoparticles, [21,27,28] transitional metal (oxy)hydroxides, [29][30][31] and other derived catalysts [32,33] (Table 2). Catalysts containing low amounts of noble metals or non-noble metal catalysts are highly desired to reduce the cost of water splitting.…”

“…Batch-type cell, 1 m KOH, on Ni foam, electrode area: ≈1 cm 2 [40] MoC 2 /MoS 2 220 mV @ 1000 mA cm -2 Batch-type cell, 1 m KOH, on Ti foil, electrode area: ≈1 cm 2 [24] h-NiMoFe 97 mV @ 1000 mA cm -2 Batch-type cell, 1 m KOH, on Ni foam, electrode area: 1 cm 2 [41] GDY/MoO 3 1850 mV @ 1200 mA cm -2 Batch-type cell, 0.1 m KOH, on Cu foam, electrode area: 1 cm 2 [26] CoP HNS/CF 180 mV @ 500 mA cm -2 Batch-type cell, 0.5 m H 2 SO 4 , on carbon foam, electrode area: ≈1 cm 2 [42] 2H-Nb 1.35 S 2 420 mV @ 5000 mA cm -2 Batch-type cell, 0.5 m H 2 SO 4 , on glassy carbon, electrode area: not referred to [25] Ta-TaS 2 398 mV @ 2000 mA cm -2 Batch-type cell, 0.5 m H 2 SO 4 , material itself as both electrodes and catalyst, electrode area: ≈1 cm 2 [43] MoC 2 /MoS 2 227 mV @ 1000 mA cm -2 Batch-type cell, 0.5 m H 2 SO 4 , on Ti foil, electrode area: ≈1 cm 2 [24] α-MoB 2 334 mV @ 1000 mA cm -2 Batch-type cell, 0.5 m H 2 SO 4 , on Cu foil, electrode area: ≈1 cm 2 [44] PtGa 113 mV @ 600 mA cm -2 Batch-type cell, 0.5 m H 2 SO 4, material itself acts as both electrode and catalyst, electrode area: not referred to [21] HC-MoS 2 /Mo 2 C 414 mV @1000 mA cm -2 Batch-type cell, 0.5 m H 2 SO 4 , on Cu foam, electrode area: ≈1 cm 2 [45] Ta-TaS 2 (HER) || IrO 2 1.98 V @ 1000 mA cm -2 PEM electrolyzer, ambient condition, electrode area: 1 cm 2 [43] CoP (HER) || IrO x 2.02 V @ 1860 mA cm -2 PEM electrolyzer, at 55 °C, 400 psi, electrode area: 86 cm 2 [22] Pd/PG (HER) || RuO 2 2.32 V @ 2000 mA cm -2 PEM electrolyzer, at 80 °C, catalyst on PEM, electrode area: 25 cm 2 [46] Mo 3 S 13 -NCNT (HER) || IrO 2 2.36 V @ 4000 mA cm -2 PEM electrolyzer, at 80 °C, on carbon cloth, electrode area: 5 cm 2 [47] MoP|S-CB (HER) || Ir/C 1.81 V @ 500 mA cm -2 PEM electrolyzer, at 80 °C, on carbon paper, electrode area: 5 cm 2 [23] NiCu mixed metal oxide (HER) || Ir/C 2.0 V @ 1850 mA -2 AEM electrolyzer, at 50 °C, on carbon paper, electrode area: 25 cm 2 [48] OER Co-doped FeNi carbonate hydroxide 254 mV @ 500 mA cm -2 Batch-type cell,1 m KOH, on Ni foam, electrode area: ≈1 cm 2 [29] Nanostructured NiFe (oxy)hydroxide 261 mV @ 500 mA cm -2 Batch-type cell, 1 m KOH, on Ni foam. electrode area: ≈1 cm 2 [30] Ni-Fe oxyhydroxide @ NiFe alloy 248 mV @ 500 mA cm -2 258 mV @ 1000 mA cm -2 Batch-type cell, 1 m KOH, on Ni foam.…”

Engineering transition metal catalysts for large-current-density water splitting

“…More recently, Guo et al realized the apparent HER activity enhancement in the MoO 3 catalyst by coupling with graphdiyne (GDY). 85 To be specific, they have constructed C-O-Mo bonds between GDY and MoO 3 through the interfacial sphybridized carbon atom design. It is revealed that the unique "sp C-O-Mo hybridization" in GDY/MoO 3 facilitates the formation of a new type of active site (non-oxygen vacancy sites), explosive exposure of more active sites, fast charge transfer, and dissociation process of H 2 O molecules (Fig.…”

Bifunctional catalysts of Ni nanoparticle coupled MoO2nanorods for overall water splitting

“…3d, the O 1s peaks at 530.1, 531.5, and 532.9 eV are assigned to the hydroxy species of the metal-O band (denoted as lattice O), oxygen vacancies (denoted as vacancy O), and absorbed water molecules (denoted as absorbed O), respectively. 42 The Ni 2p and Mo 3d XPS spectra of CNMO-700 after acid etching are shown in Fig. S7.…”