“…Typically, the industrially-used Raney Ni electrocatalysts operating at 500 mA cm −2 for overall water splitting required a cell voltage of 2.4 V, [13] which largely exceeds the thermodynamic potential of 1.23 V. To date, the overall water splitting catalyzed by NiMoO x @NiMoS x , [14] FeP@Ni 2 P [15] and NiMoN@NiFeN [16] still required the cell voltages as high as 1.75, 1.73 and 1.72 V, respectively, at 500 mA cm −2 . Although tremendous progress by regulation of phase structure, defects, interface, and active sites has been developed to boost activities of electrocatalysts for robust water splitting, [17][18][19][20][21][22][23][24][25][26][27] traditional electronic regulation to construct a semiconductor heterostructure toward overall water splitting is difficult to realize for durable and fast Volmer H* and Heyrovsky H 2 generation for large-current operation, owing to the instinct of relatively low electronic conductivity and high ohmic contact resistance [11,28,29] (Figure 1a).…”