Triggering the Intrinsic Catalytic Activity of Ni-Doped Molybdenum Oxides via Phase Engineering for Hydrogen Evolution and Application in Mg/Seawater Batteries

Abstract

Molybdenum oxides have been regarded as promising non-noble metal electrocatalysts for hydrogen evolution reaction (HER) due to their low cost, nontoxicity, and chemical stability. However, promoting the intrinsic catalytic activity of molybdenum oxides is crucial for achieving high HER performance. Herein, we demonstrate that the intrinsic HER activity of Nidoped molybdenum oxides is triggered via a thermal treatment induced phase engineering strategy. The HER overpotential at 10 mA cm −2 decreases from 493 mV (1 M KOH) and 818 mV (seawater) over Ni-doped molybdenum trioxide (Ni-MoO 3 ) to only 234 and 412 mV over Ni-doped molybdenum dioxide (Ni-MoO 2 ), respectively. Moreover, the electrochemical surface areas (ECSAs)-normalized current density over Ni-MoO 2 , as compared to Ni-MoO 3 , is at least a 35-fold increase in alkaline (at −0.2 V vs reversible hydrogen electrode (RHE)) and a 59-fold increase in seawater (at −0.4 V vs RHE), confirming the significantly triggered intrinsic HER activity via engineering orthorhombic MoO 3 to monoclinic MoO 2 . Finally, an assembled Mg/seawater battery with the Ni-MoO 2 cathode reveals a peak power density of 6.54 mW cm −2 and a continuous stable discharge for over 24 h. This study offers a facile strategy for promoting the intrinsic HER activity of non-noble metal electrocatalysts.

Anderson-Type Polyoxometalate-Assisted Synthesis of Defect-Rich Doped 1T/2H-MoSe2 Nanosheets for Efficient Seawater Splitting and Mg/Seawater Batteries

“…Impressively, the HER current density of Co-MoSe 2 exceeds that of the benchmark 20% Pt/C as the applied potential is negative at −0.38 V, suggesting a potential industrial application of the catalyst in seawater. In addition, the HER activity of the Co-MoSe 2 in seawater is much superior to the recently reported Mo-based electrocatalysts as listed in Table S3, including CoMoP@C (450 mV), Ni-MoO 2 (412 mV), Mo 2 C-MoP (346 mV), and Mo 2 C (420 mV) Figure b shows that Co-MoSe 2 has a Tafel slope of 142 mV dec –1 , which is obviously smaller than those of Pt/C (148 mV dec –1 ), Fe-MoSe 2 (177 mV dec –1 ), Ni-MoSe 2 (149 mV dec –1 ), and pure MoSe 2 (187 mV dec –1 ), implying its faster HER kinetics.…”

Recent advances in transition metal‐based electrocatalysts for seawater electrolysis

“…Moving towards the catalyst with low cost and high activity, great progress of TM compound has been made for sea water electrolysis, as shown in Table 1, which is practically feasible due to its abundant reserves 24,25 . As reported, TMNs, TMPs, TMCs, TMDs, TMOs(OH), and so on have been explored to be competitive electrocatalysts with high activity, corrosion resistance and optimal conductivity in seawater solution 24,26‐29 . Therefore, in this section, TM‐based electrocatalysts are introduced in detail.…”

“…24,25 As reported, TMNs, TMPs, TMCs, TMDs, TMOs(OH), and so on have been explored to be competitive electrocatalysts with high activity, corrosion resistance and optimal conductivity in seawater solution. 24,[26][27][28][29] Therefore, in this section, TM-based electrocatalysts are introduced in detail.…”

“…Recently, great progress of TM compounds has been made toward seawater electrolysis, which makes the process more practically feasible due to its abundant reserves 24,25 . As reported, transition metal nitrides (TMNs), transition metal oxides (TMOs), transition metal phosphides (TMPs), transition metal carbides (TMCs), transition metal dichalcogenides (TMDs), and metal‐organic frameworks (MOFs) have been explored to be competitive electrocatalysts with high activity, corrosion resistance and optimal conductivity in seawater solution 24,26‐29 . In addition, interest in the area of TM‐based research is anticipated to increase further and a review of recent advances and challenges of TM‐based materials for electrocatalytic seawater separation is highly desirable 24 …”

“…24,25 As reported, transition metal nitrides (TMNs), transition metal oxides (TMOs), transition metal phosphides (TMPs), transition metal carbides (TMCs), transition metal dichalcogenides (TMDs), and metal-organic frameworks (MOFs) have been explored to be competitive electrocatalysts with high activity, corrosion resistance and optimal conductivity in seawater solution. 24,[26][27][28][29] In addition, interest in the area of TM-based research is anticipated to increase further and a review of recent advances and challenges of TM-based materials for electrocatalytic seawater separation is highly desirable. 24 Guided by this, we provide a review that summarizing the fundamentals and challenges associated with electrocatalytic seawater splitting, and then outlining the recent development of TM-based materials for electrocatalysis in seawater, which is reflected in Figure 1.…”