Topics in Current Chemistry (2019) 377:4
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4.2 Water Splitting
Electrochemical water splitting, including HER at the cathode and OER at the
anode, has attracted attention for hydrogen generation. To reduce the accompanying energy consumption, water electrolysis is usually carried out in either acidic
or alkaline conditions [79, 80]. The efficiency of HER in acidic conditions is
higher than that in alkaline conditions [81]. Intensive research has focused mainly
on acidic HER catalysts [82–84]. The development of OER catalysts in acidic
conditions has been relatively slow, because metal compounds are generally
not stable under these harsh conditions, with the exception of noble Ir/Ru-based
materials [81, 85], although great progress has been made in OER under alkaline
conditions [86, 87]. To date, Pt/Pt–Ru have been found to be the best HER catalysts in both acidic and alkaline conditions, while Ir/Ru are the best OER catalysts in acidic media.
Like ORR, development of single-atom metal supported on carbons is an effective strategy for replacing nanosized noble metals for water splitting. Cheng et al.
reported that single-atom Pt supported on N-doped graphene prepared by ALD
showed significantly enhanced HER catalytic activity (up to 37 times) and high
Fig. 6 a Schematic showing the preparation of N-doped CNT-based single-atom Fe catalyst. b HAADFSTEM image of CNT-based single-atom Fe catalyst. c ORR polarization curves of CNT-based singleatom Fe catalyst and reference samples in acidic media [77]
Reprinted from the journal
138
1 3
4.2 Water Splitting
Electrochemical water splitting, including HER at the cathode and OER at the
anode, has attracted attention for hydrogen generation. To reduce the accompanying energy consumption, water electrolysis is usually carried out in either acidic
or alkaline conditions [79, 80]. The efficiency of HER in acidic conditions is
higher than that in alkaline conditions [81]. Intensive research has focused mainly
on acidic HER catalysts [82–84]. The development of OER catalysts in acidic
conditions has been relatively slow, because metal compounds are generally
not stable under these harsh conditions, with the exception of noble Ir/Ru-based
materials [81, 85], although great progress has been made in OER under alkaline
conditions [86, 87]. To date, Pt/Pt–Ru have been found to be the best HER catalysts in both acidic and alkaline conditions, while Ir/Ru are the best OER catalysts in acidic media.
Like ORR, development of single-atom metal supported on carbons is an effective strategy for replacing nanosized noble metals for water splitting. Cheng et al.
reported that single-atom Pt supported on N-doped graphene prepared by ALD
showed significantly enhanced HER catalytic activity (up to 37 times) and high
Fig. 6 a Schematic showing the preparation of N-doped CNT-based single-atom Fe catalyst. b HAADFSTEM image of CNT-based single-atom Fe catalyst. c ORR polarization curves of CNT-based singleatom Fe catalyst and reference samples in acidic media [77]
Reprinted from the journal
138