DFT-assisted rational design of CoMxP/CC (M = Fe, Mn, and Ni) as efficient electrocatalyst for wide pH range hydrogen evolution and oxygen evolution

Rational design of highly active transition-metal phosphides for electrocatalyzing overall water splitting in a wide pH range assisted by first-principle calculations can efficiently save the developing cost and hence is quite attractive. Under the guidance of density-functional theory (DFT) calculations that the introduction of dopants (Fe, Mn, and Ni) into CoP could promote the hydrogen evolution reaction (HER) performances, a series of binder-free CoMxP/carbon cloth (CC; M = Fe, Mn, and Ni; x = 0, 0.05, 0.2, 0.5, and 1) were fabricated. Both experimental measurements and DFT calculations confirm the electronic modulation of dopants. DFT calculations further reveal that the modulated electronic structure promotes the electronic conductivity, favors the adsorption of key species, and consequently promotes the electrochemical performances. As predicted, the bimetallic phosphides demonstrate excellent HER performances in alkaline, acidic, and alkaline simulated seawater solutions and also deliver excellent oxygen evolution reaction (OER) performances, overwhelming the commercial RuO2. Benefiting from the modulated electronic structure and the hierarchical structure with massive CoFe0.05P zero-dimensional (0D) quantum dots anchored on two-dimensional (2D) N-doped porous carbon, CoFe0.05P delivered the best HER in four kinds of electrolytes (η10 of 73 mV in an alkaline simulated seawater solution) and OER in two kinds of electrolytes (η10 of 264 mV in an alkaline solution) with excellent stability of 45 h in the alkaline solution. The assembled CoFe0.05P/CC//CoFe0.05P/CC with the electrodes folded by 180° can still maintain a low cell potential of 1.62 V at 10 mA·cm−2. This work proves the feasibility of the reported rational design strategy of developing efficient electrocatalysts for overall water splitting in a wide pH range.