Unconventional direct synthesis of Ni3N/Ni with N-vacancies for efficient and stable hydrogen evolution

• Published in: Energy & environmental science Vol. 15; no. 1; pp. 185 - 195
• Main Authors: Zhang, Doudou, Li, Haobo, Riaz, Asim, Sharma, Astha, Liang, Wensheng, Wang, Yuan, Chen, Hongjun, Vora, Kaushal, Yan, Di, Su, Zhen, Tricoli, Antonio, Zhao, Chuan, Beck, Fiona J, Reuter, Karsten, Catchpole, Kylie, Karuturi, Siva
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2022
• Subjects: Catalysts; Catalytic activity; Chemical synthesis; Corrosion resistance; Electrical resistivity; Electrochemistry; Electrolysis; Electrolytic cells; Energy conversion; Feasibility; Hazardous areas; High temperature; Hydrogen evolution; Magnetron sputtering; Metal nitrides; Photocathodes; Pourbaix diagrams; Stability; Substrates; Transition metals; Vacancies; Wettability; Working conditions
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/d1ee02013g

Transition metal nitrides are a fascinating class of catalyst materials due to their superior catalytic activity, low electrical resistance, good corrosion resistance and earth abundance; however, their conventional synthesis relies on high-temperature nitridation processes in hazardous environments. Here, we report a direct synthesis of Ni3N/Ni enriched with N-vacancies using one-step magnetron sputtering. The surface state of Ni3N(001) with 75% N-vacancies is hydrogen-terminated and exhibits four inequivalent Ni3-hollow sites. This leads to stronger H* binding compared to Ni(111), and is affirmed as the most stable surface termination under the electrochemical working conditions (pH ≈ 13.8 and E = −0.1 V) from the Pourbaix diagram. The Ni3N/Ni catalyst shows low crystallinity and good wettability and exhibits a low overpotential of 89 mV vs. RHE at 10 mA cm−2 in 1.0 M KOH with excellent stability over 3 days. This performance closely matches that of the Pt catalyst synthesized under the same conditions and surpasses that of other reported earth-abundant catalysts on planar substrates. The application of Ni3N/Ni as a cocatalyst on Si photocathodes produces an excellent ABPE of 9.3% and over 50 h stability. Moreover, its feasibility for practical application was confirmed with excellent performance on porous substrates and robustness at high operating currents in zero-gap alkaline electrolysis cells. Our work demonstrates a general approach for the feasible synthesis of other transition metal nitride catalysts for electrochemical and photoelectrochemical energy conversion applications.