Crystalline Ni(OH)₂/Amorphous NiMoO_x Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

Abstract

electrocatalysts, NiMo-based carbides, [10,11] nitrides, [12,13] sulfides, [14] phosphides [15] as well as NiMo-alloy electrocatalysts [16][17][18][19][20][21] can possess remarkable HER capabilities. As the variety of NiMo-based catalysts being enriched, pure NiMo-based oxide or hydroxides have rarely been explored as HER catalysts, instead they usually are coupled with other active components for realizing efficient HER. [22,23] Meantime, it has been proved the effect of accelerating water dissociation of Ni(OH) 2 in alkali [24,25] and the superior catalytic performance of MoO 2 . [26] Herein, we speculate that the alkaline HER performance of NiMo-based (hydr) oxide is greatly underestimated.Inspired by above considerations, a novel 3D porous integrated electrocatalyst Ni(OH) 2 -NiMoO x /NF constituted of crystalline Ni(OH) 2 and amorphous NiMoO x was fabricated through ZnO templateassisted electrodeposition and subsequent KOH soaking operations. Interestingly to note, soaking alters the crystallinity of the amorphous precursor and triggers phase transformation, generating the crystalline/amorphous electrocatalyst. To deliver current densities of 10 and 200 mA cm −2 for alkaline HER, this catalyst requires overpotentials of 36 and 176 mV, respectively. It also displays a much decreased Tafel slope (38 mV dec −1 ) compared with the precursor (92 mV dec −1 ), illustrating an optimized reaction kinetics from Volmer-Heyrovsky step to Heyrovsky step. And the overpotential is only 13 mV increased after the multicurrent step stability test, manifesting its excellent durability. When composed into the two-electrode electrolyzer for ureaassisted electrolysis, a cell voltage of 1.42 V is barely demanded to achieve 10 mA cm −2 . Meanwhile, the catalytic activity can sustain for more than 40 h without declination, proving the feasibility of realizing high-efficient HER through urea-assisted electrolysis. Furthermore, the synergy effect between crystalline Ni(OH) 2 and amorphous NiMoO x are identified through contrastive experiments and the Fourier transform infrared spectroscopy (FTIR) results: Ni(OH) 2 serves for accelerating the dissociation of water (Volmer step) in alkali to generate H*, while amorphous areas are the active sites for H* adsorption and desorption through subsequent Heyrovsky and Tafel steps. This work not only fabricates the electrocatalyst of NiMo-based (hydr) oxides with brilliant HER and urea oxidation reaction (UOR) capabilities, but also discovers a new pathway for designing mixed-crystal materials for other catalysis systems.The Ni(OH) 2 -NiMoO x /NF electrocatalyst was prepared via electrodeposition and soaking operations exhibited in The achievement of effective alkaline hydrogen production from water electrolysis is an active field of research. Herein, an integrated electrode composed of crystalline Ni(OH) 2 and amorphous NiMoO x is fabricated onto nickel foam (denoted as Ni(OH) 2 -NiMoO x /NF). The hydrogen evolution reaction (HER) kinetics are optimized along with phase transformation process...

Etching‐Doping Sedimentation Equilibrium Strategy: Accelerating Kinetics on Hollow Rh‐Doped CoFe‐Layered Double Hydroxides for Water Splitting

“…Considering these results, the reaction process driven by Rh doped CoFe-ZLDH follows the Volmer-Heyrovsky mechanism to achieve a rapidly increasing hydrogen evolution rate under the application of voltage. As shown in Figure 3c and Table S2 in the Supporting Information, Rh-doped CoFe-ZLDH outperforms many other previously reported state-of-art HER electrocatalysts, such as Rh 2 P, [41] L-Ag, [42] single atomic Co supported on phosphorized carbon nitride nanosheets (Co 1 /PCN), [43] NiMoO x -Ni(OH) 2 /NF, [44] interface catalyst consisting of atomic cobalt array covalently bound to distorted 1T MoS 2 nanosheets (SA Co-D 1T MoS 2 ), [45] Pt clusters in hollow mesoporous carbon spheres (Pt 5 /HMCS), [46] Ni-Fe nanoparticle (Ni-Fe NF), [39] oxygen vacancy enrich CoFe 2 O 4 (r-CFO), [47] CoFeP TAPs/Ni, [48] nickel-molybdenum-nitride nanoplates on carbon fiber cloth (Ni-Mo-N/CFC), [40] Ru SA -N-S-Ti 3 C 2 T x , [9] W-CoP NAs-CC, [49] MoP@NCHs-900, [50] Co 9 S 8 @C, [51] and Co 0.31 Mo 1.69 C/MXene/NC. [52] The cyclic voltammetry (CV) method was utilized to calculate the electrochemical double-layer capacitance (C dl ) to reflect the electrochemical active area (ECSA).…”

Electrodeposition: Synthesis of advanced transition metal-based catalyst for hydrogen production via electrolysis of water

“…ZnO nanorods and porous oxides of silicon and aluminum are regarded as typical self-sacrifice template to grow nanoarray [58,[116][117][118]. Dong et al [119] have constructed nanoarray Ni(OH) 2 /NiMoO x by three steps in Fig. 5 (b).…”

MOFs‐Derived Carbon‐Based Metal Catalysts for Energy‐Related Electrocatalysis

“…[1][2][3][4][5][6] Therefore, utilizing energy-related storage and conversion technologies to power the future society are hailed as the new and sustainable green energy methods to achieve environmentally benign. Among various next-generation renewable energy systems, the electrochemical devices, such as fuel cells, [1,7,8] water splitting electrolyzers, [9][10][11][12][13][14] metal-air batteries, [15,16] carbon dioxide reduction, [17][18][19] and nitrogen reduction, [20][21][22] are expected largely to fulfill the sustainable development in the future. Fundamentally, these electrochemical devices usually involve several familiar redox reactions, such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction Electrochemical devices, as renewable and clean energy systems, display a great potential to meet the sustainable development in the future.…”